C<$5. '3 -VW/5 c//?e . w 3 I n. v a to a U.S. DEPARTMENT OF COMMERCE Juanita M. Kreps, Secretary National Oceanic and Atmospheric Administration Richard A. Frank, Administrator National Marine Fisheries Service National Marine Fisheries Service (NMFS) does not approve, rec- nmend or endorse any proprietary product or proprietary material itioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro- jtion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication. CONTENTS Page Identity 1 1.1 Nomenclature 1 1.2 Taxonomy 1 1.3 Morphology 2 Distribution 3 2.1 Total area 3 2.2 Differential distribution 4 2.3 Determinants of distribution 4 2.4 Hybridization 5 Bionomics and life history 5 3.1 Reproduction 5 3.2 Preadult phase 6 3.3 Adult phase 9 3.4 Nutrition and growth 12 3.5 Behavior 23 Population 25 4.1 Structure 25 4.2 Abundance and density 26 4.3 Natality and recruitment 29 4.4 Mortality and morbidity 30 4.5 Dynamics of the population as a whole 31 4.6 The population in the community and the ecosystem 31 Fishing 34 5.1 Fishing equipment 34 5.2 Fishing areas 35 5.3 Fishing seasons 35 5.4 Fishing operations and results 36 Protection and management 36 6.1 Regulatory (legislative) measures 36 6.3 Control or alteration of chemical features of the environment 36 6.4 Control or alteration of the biological features of the environment 39 Pond fish culture 39 7.1 Procurement of stock 39 7.2 Spawning 39 in Synopsis of Biological Data for the Winter Flounder, Pseudopleuronectes americanus (Walbaum) GRACE KLEIN-MacPHEE 1 ABSTRACT This monograph contains a synopsis of selected pertinent papers covering biological and tech- nical data of the winter flounder, Pseudopleuronectes americanus, including life history, taxonomy, physiology, disease, ecology, population dynamics, commercial and sports fishery, behavior, environ- mental effects, and culture. One hundred and fifty-four published reports and 12 unpublished reports are covered. Twenty-one figures are included. Literature up to and including 1976 is covered. 1 IDENTITY 1.1 Nomenclature After Jordan et al. 1930:227 and Norman 1934:345. 1.11 Valid scientific name Pseudopleuronectes americanus (Walbaum). 1.12 Subjective synonomy Pleuronectes. Schoepf 1788. Schrift. Ges. Nat. Freunde Berlin, VIII, p. 148. Pleuronectes americanus Walbaum 1792. Artedi Ichth. (3), ed. 2, p. 113 (based on the flounder of Schoepf). Pleuronectes planus Mitchill 1814. Rep. Fishes New York, p. 8. Platessa plana. Storer 1893. Boston J. Nat. Hist., ii, p. 475; Rep. Ichth. Mass., p. 140. Platessa pusilla De Kay 1842. Nat. Hist., New York (Fish), p. 296, pi. xivll; fig. 153 (New York). Pseudopleuronectes planus. Bleeker 1862. Versl. Akad. Wet. Amsterdam, xiii, p. 428. Pseudopleuronectes americanus. Gill 1864. Proc. Acad. Nat. Sci. Phila., xvi, p. 216. Pseudopleuronectes dignabilis Kendall 1912. Bull. U.S. Bur. Fish., xxx, (1910), p. 392, pi. lvii (Georges Bank). 1.2 Taxonomy 1.21 Affinities Suprageneric Phylum — Chordata Subphylum — Vertebrata 'U.S. Environmental Protection Agency. Environmental Research Laboratory, South Ferry Road, Narragansett, RI 02882. Class — Osteichthys Order — Pleuronectiformes (Heterosomata) Family — Pleuronectidae Generic (data from Norman 1934) Pseudopleuronectes. Bleeker 1862. Versl. Akad. Wet. Amsterdam, xiii. p. 428. [Pleuronectes planus Mitchill]; Norman 1933, Ann. Mag. Nat. Hist. (10) xi, p. 220. Limandella. Jordan and Starks 1906. Proc. U.S. Natl. Mus., xxxi, p. 204. [Pleuronectes yokohamae Giinther.) Generic — Body ovate, compressed. Eyes on right side separated by narrow naked or scaled ridge, upper eye close to edge of head; postocular ridge, if present, rugose; snout and eyeballs not scaled. Olfactory laminae, paral- lel, without rachis. Mouth moderate sized, length of maxillary on blind side less than one-third that of head, jaws and dentition stronger on blind side, no more than ■Mx teeth on ocular side of either jaw. teeth compact in- cisorlike, close-set, sometimes forming continuous cut- ting edge, not enlarged anteriorly, uniserial in both jaws; vomer toothless. Gill rakers few, lower pharyngeals nar- row. 120-180 mm in length, slender, not much ap- proximated anteriorly, inner edges evenly curved, each with widely separated rows of conical teeth. Dorsal fin less than 85 rays beginning behind posterior nostril of blind side and above eye; all rays simple, some scaled on ocular side; tip of first interhaemal spine projecting in front of anal fin which has less than 65 rays. Pectoral fin of ocular side usually larger than one on blind side; mid- dle rays branched. Caudal fin 13 or 14 branched rays; caudal peduncle short to moderate in length. Scales small, adherent, imbricate (at least anteriorly) ctenoid or cycloid; spinules, if present, short, few; no supplementary scales, lateral line curved above pectoral fin, supratem- poral branch is present without posterior prolongations. Vent median or slightly on blind side between pelvics. Intestine narrow, elongate, with three or more coils; 3+1 pyloric appendages moderate or rather elongate. Three species, one from Atlantic coast of North America; two from Japan. Specific Pseudopleuronectes americanus (Walbaum 1792) (Fig. 1). A. Interorbital ridge nearly naked; tips of gill rakers sharply pointed; 68-75 scales in lateral line; den- tal formula 2 Figure 1 .—Adult winter flounder. Type — not traced. Lateral line nearly straight, dorsal fin originates op- posite forward edge of eye and is nearly equal in height throughout its length. Ventral fins alike on two sides of body, both separated. Synopsis of the species is taken from Norman (1934:342). Synopsis of the Species I. Eyes separated by a ridge, which is naked or scaled, width less than one-fourth diameter of eye; postocular ridge rugose. + 14-23 2-6 + 19-24 1. P. herzensteini. B. Interorbital ridge scaled; tips of gill rakers rounded or obtusely pointed; 75-90 scales in lateral line; dental formula 0-3 + 8-16 2. P. yokohamae. 0-4 + 12-20 II. Interorbital space flat, scaled, width one-third to one- half diameter of eye; postocular ridge not rugose; 78- 89 scales in lateral line 3. P. americanus. 1.22 Taxonomic status Morpho — Species. 1.23 Subspecies See section 1.31 1.24 Standard common names, vernacular names Winter flounder, blackback, Georges Bank flounder, lemon sole, flounder, sole, flatfish, rough flounder, (Bige- low and Schroeder 1953). Plie rouge, carrelet (Leim and Scott 1966). 1.3 Morphology 1.31 External morphology Gill rakers 7-8 (lower anterior arch); lateral-line scales 78-89; fin rays, dorsal 59-71(5 73), anal 47-54(x 46), pec- toral 10-11 (5-7 branched); caudal 19 (13 branched); ver- tebrae 36 (10+26); pyloric caecae 3+1; dental formula 0-2 + 10-15 0-2 + 10-17 (Norman 1934). See also Table 1. 1.32 Geographic variation In 1912 W. C. Kendall described the Georges Bank flounder as a new species, Pseudopleuronectes dig- nabilis. He stated that the most conspicuous differential characteristics of this "species" are shorter head, larger number of vertical fin rays, color, and larger size (Ken- dall 1912). There is also a different spawning season (April-May). Perlmutter (1947) compared counts of winter flounder north and south of Cape Cod and from Georges Bank. He felt that Georges Bank flounder had significantly dif- ferent dorsal, pectoral, and anal fin ray counts showing there was little mixing of this stock with other winter flounder stocks. 'Dental formula occular side + blind side (upper jaw) occularside + blind side (lower jaw) Table 1. — Comparison of fin ray counts of winter flounder by several investigators. Pectoral Reference and Dorsal rays Anal rays rays locality Kendall (1909) P. dignabilis 68-78 .f 70.6 50-54 x 52.3 (Georges Bank) 61-67 x 64.7 46-50 x 48 P. americanus Perlmutter(1947) 63.97 ± 2.51 47.83 ± 1.82 9.84 ± 0.68 North of Cape Cod 64.05 ±2.29 47.73 ± 1.88 10.08 ± 0.59 South of Cape Cod Georges Bank 68.93 ± 2.53 51.30 ± 1.96 10.58 ± 0.62 (P. dignabilis) .V i Lux etal. (1970) 64.94 48.89 Cape Cod Bay (North) 66.87 50.42 East. Vineyard Sound (South) Date Georges Bank 1963 69.53 51.94 (P. dignabilis) 1964 69.58 52.14 1966 70.28 52.61 Lux et al. (1970) compared dorsal and anal fin ray counts on winter flounder from inshore waters off Massachusetts north and south of Cape Cod and from Georges Bank. An examination of water temperature at spawning time (March-April) for 1940-56 in the National Marine Fisheries Service at V showed that, in March, water temperature range Wood " rere indicatec ear tl 1.7° to 5.4°C. This is higher than at Gloucester, Mass. The Georges Ban spawn at higher temperatures w ray number. Norman (1934) represent a distinct race with a diffe as described by Kendall (1909) (Table Lobell (1939) believed racial groups \ Long Island Sound since recoveries localities occur simultaneously wit! points relatively distant. 2 DISTRIBUTION 2.1 Total area Atlantic coast of North America fro the offshore fishing banks (40-100 m ter flounder is common from the Strait North Shore of the Gulf of St. Lawren< • Bay. The extremes of distribution are .. of the Grand Banks, the northernrru gava Bay, Labrador (Kendall 1909); and V. Beaufort, N.C., the southernmost recc (Hildebrand and Schroeder 1928). Figure 2. — Range of winter flounder. 3 45° -40° 2.2 Differential distribution 2.21 Eggs, larvae, juveniles Marine Research, Inc.' mapped larval distribution in Narragansett Bay (Fig. 3). The most extensive work on differential distribution of eggs, larvae, and juveniles was done by Pearcy (1962a) in the Mystic River estuary, Conn. Spawning took place in the upper estuary. Young fish demonstrated both horizontal and vertical dif- ferences in distribution. Figure 3. — Distribution of winter flounder larvae in Narragansett Bay (Marine Research Inc. 1974, see text footnote 3). Horizontal distribution — During the early larval period ("March to April prior to metamorphosis), the den- sity of winter flounder larvae was 15 times greater in the upper Mystic River estuary than in the lower estuary. Later in spring, upper estuarine density declined. By May no larvae were caught in the upper estuary indicat- ing that larvae moved down into the lower estuary. In the early season there was no difference in average length of larvae from the upper or lower estuary. During March and April the smallest sizes were found in the lower es- tuary and by mid-April the largest sizes were taken here. Vertical distribution — Larvae had a passive sinking rate of 14 mm/s in seawater with a specific gravity of 1.022, so they were nonbuoyant and located near the bot- tom, partially benthic. The small larvae are poor swim- mers which swim vertically in a 90° climb, stop, rotate 180°, and sink passively (Pearcy 1962a). Perlmutter (1947) found the larvae spawn in shallow water in southern New England and New York. Larvae remain in shoal water near shores of bays and estuaries. As they grow older they tend to move into deeper water; entering the commercial and sport fisheries catch in the second and third years. De Sylva et al. (1962) 4 reported that in the Delaware River estuary, Indian River Bay seemed to be an impor- tant nursery ground for young which first appeared in early June. Larvae were collected in late winter. Work done by Derickson and Price (1973) in the Indian River Bay area of the Delaware River and by McCracken (1963) on movements of immature flounders in Passama- quoddy Bay, Canada, supported the statement that, in general, in northern waters immature flounder occur in- shore and move offshore during winter. Lux et al. (1970) collected spent and spawning females off Georges Bank, Mass. The population spawns off- shore and larvae and juveniles remain on the spawning area separated from nearby shore populations. 2.22 Adults— See section 3.53 2.3 Determination of distribution Perlmutter (1947) stated that the predominant phys- ical forces affecting movements of eggs and larvae in spawning habitats are wind and tide, but effects of these are reduced by eggs being demersal and adhesive, with early pelagic stages remaining in back waters of bays and inlets. Pearcy (1962a) attributed the larval distribution in- shore and close to the bottom to the fact that they are nonbuoyant. When not actually swimming they sink; and therefore, are not carried away by outward moving surface currents. The survival value of this is that it might reduce offshore dispersal, an important factor in loss rate for small larvae. McCracken's (1963) laboratory studies of winter floun- der reactions to light showed that small (60-90 mm TL (total length) ) immature flounders are positively photo- tropic; medium (120-180 mm TL) flounders avoid light. He theorized that where flounder are found in shallow water during summer, the differential distribution between young immature and older immature may result from a different behavior pattern with size and maturity in relation to light. Marine Research Inc. 1974. 19th Rome Point Investigations Narra- gansett Bay, Ichthyoplankton Survey Final Report to the Narragansett Electric Company. Me Sylva, D. P., F. A. Kalber, Jr., and C. N. Shuster, Jr. 1962. Fishes and ecological conditions in the shore zone of the Delaware River Estuary with notes on other species collected in deeper waters. Univ. Del. Mar. Lab., Inf. Ser. Pub!. No. 5, 164 p. Experiments by Huntsman and Sparks (1924) and Battle (1926) on resistance to temperature stress showed that younger fish were more tolerant of high tempera- tures (29°-30°C) than older fish, which might also ac- count for their being located in shallower waters in summer. 2.4 Hybridization Nichols (1918) described a fish from the New York market believed to be a hybrid, Pseudopleuronectes americanus X Limanda ferruginea. Considering the Georges Bank flounder as a separate species, Morrow (1944) reported a record winter flounder (560 mm TL, 2,649 g) which appeared to be intermediate between P. americanus and P. dignabilis. 3 BIONOMICS AND LIFE HISTORY 3.1 Reproduction 3.11 Sexuality Winter flounder have separate sexes; there is little sex- ual dimorphism. Norman (1934) stated that scales on the blind side of males are ctenoid instead of cycloid, giving them a rough feeling. Perlmutter (1947) confirmed this generally, but mentioned that often large females have rough scaled blind sides. 3.12 Maturity Winter flounder in the New York region mature at 2-3 yr when they are 200-250 mm TL long (Perlmutter 1947). Kennedy and Steele (1971) gave the age of maturity of flounder from Canada as age VI for males and VII for females. Fifty percent of the females and males were mature at 250 and 210 mm, respectively. Maturity may be related to size and not age; therefore, northern floun- der may be older at maturity than southern ones. 3.13 Mating No distinct pairing has been observed (Breder 1922). See 3.16. 3.14 Fertilization external (Breder 1922) 3.15 Gonads In Long Pond, Newfoundland, male gonads began to enlarge earlier than female and males reached spawning stage before females. Ripening began in September, progressed slowly during winter months, and spawning took place March-June (Kennedy and Steele 1971). Dunn and Tyler (1969) studied ovarian anatomy of winter flounder. They described the ovary as being an adaptation of the vertebrate compact ovary. It differs from most teleost ovaries in having a relatively short hilus and mesovarium. Ovaries are connected anteriorly to the peritoneum by a short mesovarium; arteries and veins pass through the hilus. Four oocyte types could be distinguished morphologically throughout the yearly cycle: 1) Small immature — 10-80 p diameter, irregular in shape, sometimes angled, darkly staining (basophilic) containing no yolk or fat droplets; nucleus with one or two large nucleoli. 2) Large immature — 80-150 M round, yolkless con- taining some fat droplets, granular looking cytoplasm. Nucleus with several darkly staining nucleoli around the periphery. 3) Maturing oocytes — 150 ^ massive deutoplasm fat and yolk deposits, small protoplasm, prominent theca. Visible yolk deposition occurs at 150 ^ . At ovulation, diameter 40-850 ^ . 4) Atretic or regressing oocytes — Shrinkage of zona radiata away from theca. Disorganized cellular struc- ture including rupture of the nucleus and wrinkling of the theca, resorption of yolk and fat which leaves a mass of folded theca often containing dark staining amor- phous material. Three states of ovary development based on biological examination of follicular development were present for fish held in tanks: 1) Resting ovaries — Contain no oocytes with yolk deposits, have large intraovarian spaces, relatively thick walls. (Those on reduced rations often did not have thick walls). 2) Ripening ovaries — Contained maturing oocytes as well as atretic and immature ones. 3) Regressing ovaries — Portion of large immature oocyte had begun vitellogenesis normally but at the time of sampling were atretic. Ovaries less emaciated than resting types, immature oocytes more densely arranged. The frequency distribution of oocyte sizes in resting ovaries showed bimodal distribution. Dunn and Tyler (1969) hypothesized a 2- or 3-yr cycle. Dunn (1970) found individual fish vary in their state of development at any given time, strengthening the 3-yr- cycle hypothesis. He studied fish 340-450 mm TL from September to December, and presented evidence for autumn growth of yolkless oocytes which would tend to split oocytes into two size groups. The proportion of small immature oocytes remained low so few oocytes were added to immature follicles. Increase in proportion of eggs in larger size classes (80- 100 /i) with reduction in number of small eggs represented growth of a portion of the oocytes. Larger oocytes can be tentatively identified with those oocytes that in the following summer form the stock of large immature follicles which begin vitel- logenesis to be spawned the next spring. Three year cycle — year 1, at least small immature oocytes become recognizable; year II they become larger immature oocytes; year III yolk is deposited and they are spawned. Fecundity studies have been summarized in Table 2. Topp (. 1968) also measured ova density and found it ranged from 6.082 to 18.963 eggs/g of ovary with a mean of 10,595 eggs g of ovary. Egg diameter ranged from 0.33 to 1.00 mm with a mean of 0.61 mm. There was no sig- nificant correlation between mean egg size and fish size; but egg size differed among age groups, age group three having the smallest eggs. Table 2.— Fecundity values for winter flounder. Number of eggs Age. weight or X 1.000 size (TL) offish Investigator x 500 Bigelowand Maximum 1.500 1.531 g Schroeder(1953) 435-3,329 3 yr (300-400 mm) to 5 yr (400-450 mm) Topp (1968) 210 g, 250 mm to Saila (1962a) 93-1.340 1,052 g, 430 mm x 610 x 334 mm 111 g, 220 mm to Kennedy and 99-2.604 1,300 g, 440 mm Steele (1971) x 590 x 340 mm 3.16 Spawning — Once a year (Table 3) - Spawning times vary, beginning earlier in the southern part of the fish's range and progressively later as one proceeds northward. Tagging experiments at Woods Hole and Waquoit, Mass.. performed by Nesbit (in Lobell 1939) showed that a significant number of fish returned to the same spawn- ing grounds two or more successive years. He was not able to tell if these fish remained in the bay throughout the regular season, or moved out and returned to spawn. Saila (1961) showed that winter flounder returned to the tagging locality with high frequency over the year of recovery data, after having left the area following the in- itial breeding season. (See section 3.51.) Breder (1922) described spawning habits from obser- vations made on fish held captive in large wooden tanks Table 3.- Dates of winter flounder spawning at different geographic locations from north to south. Dates Peak Area Investigator Mar. -June Long Pond, Con- Kennedy and ception Bay, Steele (1971) Newfoundland Mar. -May Apr. Booth Bay Harbor. Hahn (Pers. commun. Maine in Bigelow and Schroeder, 1953) Feb. -May — Eel Pond, Woods Sherwood and Hole, Mass. Edwards (1901) Jan. -Mav Feb. -Mar. South of Cape Bigelow and Cod and Massa- Schroeder (1953) chusetts Bay Mid Feb.- Mar. Mystic River Pearcy (1962a) Apr. estuary, Conn. Dec. -May Varies Southern New Perlmutter(1947) with water England — New temp. York Nov. -Apr. — Indian River Bay, Fairbanks et al. Del. (1971) at Woods Hole. Spawning occurred at night, between 2200 and 0330, under artificial lights. Five fish, three males and two females, took part. Previous to spawning, they (especially females) exhibited a large amount of swimming activity. The fish swam rapidly in a circle about 1 ft in diameter, counterclockwise with vent outwards. As they swam, genital products were discharged. This took 10 s, then the fish swam to the bottom. During spawning, eggs were extruded from the female, flowed along the upper side of the anal fin and over the tail to spread out in all directions. Breder (1922) believed that females must release the eggs but males can hold the milt because, if frightened or alarmed, they do not take part in the ac- tivity. I can confirm this from personal observations. See section 3.51 for information on spawning migra- tion and section 7.2 for factors influencing maturation and spawning time. 3.17 Eggs The eggs are demersal. Pearcy (1962b) showed that specific gravity with gum arabic and seawater was 1.085, and they sank in water of 30% o salinity. He believed that morphological similarities among adults, and characteristics of the larvae of those pleuronectids with demersal eggs, suggest they evolved from species with buoyant eggs. The adaptive value of demersal eggs is that they would remain in inshore nursery grounds where conditions for development are favorable. The eggs ranged from 0.71 to 0.86 mm in diameter with a mode of 0.81 mm. The spermatozoa are 0.030-0.035 mm long. Eggs are adhesive and clump together after fer- tilization, often becoming distorted and polyhedral in shape (Breder 1924). See also section 3.21. 3.2 Preadult phase 3.21 Embryonic phase Breder (1924) described the embryonic stages in eggs collected from ponds in the Woods Hole region during February when water temperature ranged from 1° to 2°C (Fig. 4). 1) Blastodisc — Large and pale amber, yolk colorless with a finely tuberculate surface. 2) First cleavage (temperature 21°C) 2V% h after fer- tilization. 3) 24 h after fertilization blastoderm has many cells. 4) 3rd day — Differentiation begins. 5) 6th day — Premature segmentation and cephaliza- tion begins. In many eggs a small sphere similar to the oil globules in pelagic eggs was observed (I believe this is Kuppfers vessicle); a few had several. Beyond this stage they disappeared. Embryo is pale amber and oil globule colorless. 6) 9 days — Embryo well differentiated, chrome yel- low chromatophores are scattered over the body. ? igure 4. — Developmental stages of winter flounder. A. Unfertilized ;gg. B. Egg with blastoderm of two cells. C. Egg with blastoderm >f four cells. D. Egg with blastoderm of eight cells. E. Egg with )lastoderm of many cells. F. Embryo in early stage of differentia- ion. G. Embryo further differentiated. Note small sphere similar o an oil globule. H. Embryo in an advanced stage of differentiation. . Egg about to hatch. (From Breder 1924.) 7) 15 days — Chromatophores have the same ap- pearance but a concentration of them as a vertical band appeared in caudal region. The heart can be seen beat- ing and the cephalic region looks finely tuberculate. After 15 days, hatching began. After hatching, eyes were sometimes unpigmented and sometimes had chrome yel- low pigment. Pigment developed in all larvae within a few days. Later the pupils became tinged with green. 8) 19 days after hatch — Pupil black and iris with metallic green iridescence. Eyes directed forward and down. Mouth is large and functional; yolk absorbed, animal symmetrical. Pigment is darker, almost orange. The temperature at which these eggs were incubated is not clear. The only temperature given (21°C) is lethal to winter flounder eggs. According to my experience, this timetable of events best corresponds to temperatures of 6°-8°C. Sullivan (1915) observed hatching of eggs which had been stripped and fertilized in the laboratory. For a day or more before hatching, fish could move within the cap- sule. Movement occurred by a series of contractions from the posterior part which tended to push the fish forward and eventually ruptured the egg capsule at right angles to the long axis of the fish's body. The fish usually freed itself from the capsule within 10 min. Scott (1929) inves- tigated effects of salinity and temperature on hatching of eggs. At 4°-5°C, 70% hatched at a maximum average time of 26 days as compared with 21 days at 0°C, and 18 days at 12°-17°C. At varying salinities (29.40 ± 2.2°/ 00 control) the highest percent hatching occurred at 7/8 and 1/8 parts salinity. The average percent hatching was lower for eggs in dilute seawater than control, and lower than the normal average. Percent hatch did not decrease linearly with decreasing salinity. He concluded that salinity has little effect on hatching but temperature is important. Rogers (1976) incubated winter flounder eggs under various conditions of temperature and salinity and found highest viable hatches occured at 3°C over a salini- ty range of 15-30°/ oo . She constructed a diagram depict- ing the qualitative effects of temperature and salinity on development and hatching of winter flounder embryos (Fig. 5) Salinity appeared to influence time of embryo mortality. At 35-45°/ 00 at all temperatures mortality usually occurred at gastrulation and abnormal develop- ment of the embryo was observed. At 5-10°/ O o embryos appeared to develop normally but died just prior to hatching; a fact which might be due to inability of the larvae to free themselves from their chorions. Analysis of variance showed salinity to be statistically more signifi- cant than temperature or the interaction of temperature and salinity. Oxygen effects were not considered. Williams (1975) studied the survival and duration of development of winter flounder eggs at several constant temperatures from — 1.8°C to 18°C with emphasis on development in the lower temperature range. Mean viable hatch was 33% for the lowest temperature tested (-1.8°C) and over 50% for 0°-10°C. Above 10°C sur- vival was lower and many embryos were abnormal with narrow fin folds, short tails, or crooked vertebral columns. Upper lethal limit was 15°C. Williams thought that the immediate cause of embryonic death at high temperatures was microbial infection as mortality was often synchronous within a dish, and dishes with more than 100 eggs had higher mortality. Oxygen depletion might also have had an effect. The median duration of days to hatching as related to temperature was de- scribed by the regression equation fitted to points from 0° to 10°C (minimum mortality range) is \nx = 3.636 - 0.158 t where x = number of days from fertilization to hatching, and t = temperature, Q 10 = 4.8. Low temper- ature adaptation in the embryo did not depend on large additions of antifreeze to the ova prior to spawning as suggested by the freezing points of mature ovaries (-0.86°-0.98°C). 3.22 Larval phase Sullivan (1915) described the larva from hatching to the end of the second month and divided larval history into four stages which he chose in order to show all diag- nostic characteristics for identification (Fig. 6). Stage 1.— Hatching (Fig. 6a) length 3.5 mm, depth 0.525 mm. A group of dark pigment spots on the pos- terior half of the body was the most important character for identification. Another pigment patch lay over the ( "\ IX! U> O 12 U. O z 10 _] 3 z 7 5 CL O _l UJ > UJ 5 o O 2 3 • V ) MA.IORI MAJORITY OF HATCHED LARVAE NORMAL ■ 75.07o COLLAPSING EGGS 5 7.5 10 15 20 25 30 35 37.5 SALINITY ( % ) 40 45 Figure 5. — Effect of salinity and temperature on hatching of winter flounder eggs (from Rogers 1976). rectum posterior to the yolk. Notochord present as straight tube. Dorsal, anal, and caudal fins represented by unbroken finfold. Yolk absorption was gradual and varied with temperature. At 4°C, 12-14 days, at higher temperatures, 8 or 9 days. Stage 2 — Yolk absorption (Fig. 6b) 12 days (approxi- mately) length 5 mm. Between stage 2 and 3 several critical changes take place: 1) migration of eyes, 2) development of fin rays, and 3) differentiation of caudal fin accompanied by up- ward bending of notochord. Stage 3 — Metamorphosing larva (Fig. 6c) 5-7 wk old, 5.8 mm long. After sixth week pigment on left side tend- ed to diminish in intensity. Stage 4 — Postlarva (Fig. 6d) about 8 wk old, 6.5 mm long, average depth 2.75 mm. In later stages there was loss of pigment on the left side and increase on the right. In 8 mm long fish the right side was devoid of pigment except for about 20 spots scattered near the snout. These were gone by the time the fish were 20 mm long. The medusae Sarsia tubulosa prey upon larvae (Pearcy 1962a). Their distribution and time of relative abun- dance coincided with winter flounder larvae. Pearcy postulated a differential predation rate, assuming that small larvae have less ability to escape the medusa, which helps explain high mortality rates for small larvae. A density dependent numerical response seemed im- probable in spite of the fact that the numbers of Sarsia Figure 6. — Larval development in winter flounder. A. Pseudo- pleuronectes americanus at hatching (3.5 x 0.523 mm). B. P. americanus at 12 days (3.0 X 0.724 mm). C. P. americanus at 6 weeks (3.8 X 1.33 mm). D. P. americanus at 8 weeks (6.5 X 2.75 mm). (From Sullivan 1915.) 8 rose and fell with that of the flounder population because the medusae do not bud. He also felt a functional response was improbable because medusae have limited sensory and locomotory abilities. Sullivan (1915) described behavior of newly emerged larvae. The larvae exhibit intermittent swimming alter- nating with resting on the bottom. If fish were kept in continuous motion for 30 min, they showed no sign of fatigue; therefore, intermittent swimming appeared to be a behavioral characteristic of the newly hatched larvae. In fish under 10 days old, no preference was shown as to which side they rested on; after 10-12 days they favored the left side. Fish 2 wk old rested on the left side 75% of the time. Food — See section 3.42. 3.23 Adolescent phase Young-of-the-year remained in waters along shores of bays and estuaries where they were spawned (Perlmut- ter 1947). Poole (1966b) collected young-of-the-year flounder in Shinnecock and Peconic Bays, Long Island. He found that saltwater coves were preferred habitats of this age group in both bays. Several important commercial and sport fishes prey upon winter flounder juveniles. A list of predators is presented in Table 4. There are no real competitors of Table 4.— Predators of juvenile winter flounder. Table 5. — Dates of field collections of winter flounder eggs, larvae, and juveniles (from north to south). Predator Citation Summer flounder, Paralichthys den tat us Striped bass, Morone saxatilis Bluefish, Pomatomus saltatrix Toadfish, Opsanus tau Cormorant, Phalocrocorax auritus auritus Harbor seals, Phoca vitulina and Phoca groenlandica Pearcy (1962a) Derickson and Price (1973) Derickson and Price (1973) Pearcy (1962a) Pearcy (1962a) Fisher and MacKenzie (1955 1 'Fisher, H. D., and B. A. MacKenzie. 1955. Food habits of seals in the Maritimes. Fish. Res. Board Can. Prog. Rep. (Atl.) 61:5-9. juvenile winter flounder reported (see The Population in the Community and the Ecosystem). A list of collec- tions of eggs, larvae, and juveniles with data, collectors, and geographical area is presented in Table 5. See also sections 3.4, 3.5, 3.53. 3.3 Adult phase 3.31 Longevity Saila et al. (1965) prepared age-length tables from fish caught in Charlestown Pond and Narragansett Bay, R.I. The oldest fish were estimated age XII. The average total length of these age XII fish was calculated as 379 mm for males and 441 mm for females. Calculations were made from otoliths and Walford plots for fish older than 3 yr. The largest recorded winter flounder (Bigelow and Schroeder 1953) was 570 mm TL and was probably con- siderably older than 12 yr. Field collections Eggs Larvae Juveniles Scott (1929); St. Andrews 20 May- N. Brunswick Mud Flats 6 June Haedrich and Haedrich June-Nov. (1974); Mystic River, Mass. Fairbanks et al. (1971); Feb. -May Mar. -June Cape Cod Canal, Mass. Breder (1924); Woods Hole Feb. Region Ponds, Mass. Herman (1963); Narragan- Feb. -June sett Bay, R.I. (3.24-7.20 mm) Marine Research Inc. Jan. -May Feb. -July (1974)' Pearcy (1962a); Upper Feb. (?) Mar. -June July-Feb. Mystic estuary, Conn. 0.75-0.96 (2.5-7.6 mm) (6-40 mm) Wheatland (1956); Long Mar. -June Island Sound (2.80-8.5 mm) Richards (1963); Long Year-round Island Sound Poole (1966b); Shinnecock June-Oct. and Peconic Bay, Long Island de Sylva et al. (1962) 2 ; Mar. -Nov. Delaware River estuary Richards and Castagna May-June (1970); Eastern Shore (27-80 mm) Virginia midway in channel and tidal creeks 'Marine Research Inc. 1974. 19th Rome Point Investigations, Narragansett Bay Ichthyoplankton Survey Final Report to the Narragan- sett Electric Company. -de Sylva et al. 1962. Fishes and ecological conditions in the shore zone of the Delaware River estuary with notes on other species collected in deeper waters. Univ. Del. Mar. Lab., Inf. Ser. Publ. No. 5, 164 p. 3.32 Hardiness Winter flounder are very hardy. They are commonly found in waters between 4 and 30% o salinity at 0°-25°C (Pearcy 1962a). Sometimes fish kills occur under extreme conditions. Nichols (1918) reported a large kill in St. Moriches Bay, Long Island, when the temperature rose to about 30°C. Bigelow and Schroeder (1953) mentioned that fish may be killed by anchor ice in winter if they are trapped in shallow water by a sudden freeze. 3.33 Competitors — See section 4.6 3.34 Predators Dickie and McCracken (1955) listed monkfish (Lophius piscatorius), dogfish (Squalus acanthias), and sea raven (Hemitripterus americanus) as predators of winter flounder in Canadian waters. Tyler 6 listed sea raven and two species of birds — blue heron and os- prey — but did not say whether these prey on juveniles or adults. 'Tyler, A. V. 1971. Monthly changes in stomach contents of demer- sal fishes in Passamaquoddy Bay, N.B. Fish. Res. Board Can., Tech. Rep. 288, 114 p. : J6 Parasites, diseases, injuries, and abnormali- ties Parasites — The principal work on parasites of winter flounder was done by Linton (1901, 1914, 1921, 1924, 1934. 1941). Heller, 6 and Ronald (1957, 1958a, 1958b, 1959. 1960. 1963) (Table 6). Diseases — Levin et al. (1972) reported methods for isolating and identifying the bacteria Vibrio anguillarium, how to identify vibriolike organisms as either V. anguillarium or V. variable, and how to diag- h Heller, A. F. 1949. Parasites of cod and other marine fish from the Baie de Chaleur region. Fish. Res. Board Can., Tech. Rep. 261, 23 p. Table 6. — Parasites of winter flounder. Parasite Site of Infestation Geographic Region Reference Protozoa Glugea microspora stephani Trichodinid Platyhelminthes Trematoda Derogenes carious Distomum appendieulatum D. grandiparum D. globeparum (?) D. citellosum D. aerolatum Stephanostomum baccatum Stephanostomum hystria Steringophorous furciger Podocotyle atomon Cnptocotyle lingua Hemiuris sp. Cestoda Bothrimonus intermedius Diplocotyle olrikii Bothriocephalus clavipes Bothriocephalus scorpii Tetrarhynchus bisculcatus Tetrarhynchus sp. Aschelminthes Nematoda Ascaris Ascaris acutus Contracaecum aduncum C. gadi Grillotia erinaceus Lacistorhynchus tenuis Scolex pleuronectis Terranova sp. Stomachinae larvae Acanthocephala Echinorhynchus laurentianus E. acus E. gadi E. sacealis Corynosoma sp. Cucullanus heterochrous Branchiura Argulus megalops A. funduli A. m. spinosus A. laticaudata Acanthochondria cornuta A. depressus Copepoda Caligus rapax I.epprjphtheirus hidpkni Isopoda Gnathia elongata intestine wal gills stomach and intestine stomach and intestine stomach and intestine stomach and intestine stomach and intestine stomach and intestine superficial musculature dermal surfaces stomach and intestine intestine skin intestine intestine intestine intestine stomach wall peritoneum stomach muscle intestine muscle intestine intestine, body cavity intestine, body walls axial musculature, body cavity exterior or pyloric caecae and intestine musculature, body cavity, surface external organs digestive tract intestine intestine skin body surface skin body surface not given not given not given not given not given not given Woods Hole Region Martha's Vineyard Bay of Fundy Canada Woods Hole Woods Hole Woods Hole Woods Hole Woods Hole Canada, Passamaquoddy Bay Canada Canada Long Island Sound Canada Passamaquoddy Bay Passamaquoddy Bay Woods Hole Woods Hole Woods Hole Long Island Canada Canada Woods Hole Woods Hole Woods Hole Canada Stunkard and Lux (1965) Lom and Laird (1969) Ronald (1960) Linton (1901) Linton (1901) Linton (1901) Linton (1901) Linton (1901) Wolfgang (1954a) Stafford (1904) Ronald (1960) Cooper (1915) Smith (1935) Ronald (1960) Cooper (1918) Ronald (1958b) Ronald (1958b) Leidy(1855) Linton (1901) Linton (1901) Linton (1901) Leidy(1904) Heller (1949)' Ronald (1963) Linton (1924) Linton (1924) Linton (1924) Ronald (1963) Ronald (1963) Gulf of St. Lawrence Ronald (1957) Gulf of St. Lawrence Linton (1901) Linton (1933) Stiles and Hassall (1894) Magdalin Island Montreuil(1955) Canada Ronald (1963) Canada Ronald (1958a) Canada Bere(1930) Canada Ronald (1958a) Rathbun(1885) Bay of Fundy Stock (1915) Woods Hole Wilson (1932) Woods Hole Wilson (1905) Woods Hole Ho (1962) Bay of Fundy Wallace (1919) Heller. A. F. 23 p. 1949. Parasites of cod and other marine fish from the Baie de Chaleur region. Fish. Res. Board Can. Tech. Rep. No. 261, 10 nose the disease vibriosis. Vibrio anguillarium was isolated from skin and muscle lesions of winter flounder from Narragansett Bay. External manifestations of dis- ease include dermal lesions usually accompanied by fin necrosis. These lesions included petichiae and ecchy- moses in their acute stage and frank ulceration in the more chronic manifestation. Necrosis of the fin began at the periphery and extended inwards including long rays. Microscopic lesions of the kidney also occurred. Characteristics of diagnostic importance to pathologists are dermal hemorrhage and ulceration, focal skeletal muscle necrosis, renal erythroblastic hyperplasia, and anemia. Organisms isolated from the lesions identified as aeromonads, plesiomonods, or vibrios by being Gram- negative, asporogenous, polar flagellate, oxidase-positive fermentative, anaerogenic rods. Stunkard and Lux (1965) described a common micro- sporidian infection of the digestive tract of winter floun- der. The disease was first reported by Linton (1901) in the Woods Hole region, and it may be identical with in- fections of European flounders caused by the parasite Nosema stephani (later transferred to the genus Glugea and referred to as G. stephani or G. hertwigi). Stunkard and Lux (1965) inspected over 1,000 winter flounder of different sizes taken from various locations in New Eng- land. Their results showed 3.5% of 751 flounder (length 120-270 mm TL) collected from Woods Hole Harbor; 16.7% of 126 flounder (length 210-500 mm TL) from Nan- tucket Shoals; 15.8% of 19 flounder (length 310-450 mm TL) from off Plymouth, Mass.; and 54.1% of small floun- der (length 41-110 mm TL) from Lake Tashmoo, Marthas Vineyard, were infected with this parasite. There was no effect of seasonal or sexual differences. The Georges Bank population (38 fish, 110-650 mm TL), isolated from the rest, showed no incidence of the disease. Infections were classified as heavy (infiltration massive, gut largely destroyed) or light (1-20 cysts in wall of intestine). Al- most all heavily infected fish were less than 80 mm long. Evidence indicates fish heavily infected during their first year of life do not survive. The site of infection was primarily the wall of the in- testine and pyloric areas. Other structures adjacent to or in contact with the gut such as the bile duct, liver, mesenterial lymph nodes, and ovary, may be involved. In light infections cysts were usually found on the external wall of the intestine; in heavy ones, the gut wall was largely supplanted by layers of cysts and the intestines had a chalk-white pebbled appearance with a rigid thickened wall. The cysts were spherical to oval and measures 0.6-1.0 mm in diameter. The walls were com- posed of laminated layers that had the structural appear- ance and staining reactions of host connective tissue. There were also masses or strands of spores scattered throughout the tissue of the gut wall often associated with distinct blood vessels. Below the connective capsule of the cyst was often a narrow layer of material contain- ing large oval, apparently pycnotic nucleii with frag- mented chromatin and distinct nucleoli. This suggested that cysts formed around a number of host cells whose cytoplasm had been consumed. Spores were oval to ovate measuring 4 X 2.5 . The basal wider end of the spore contained a large vesicle, the apical end a smaller one, the central part a band of chromatic material, and a single strand extending to the apical end. Attempts to obtain experimental infection of fishes by feeding them microsporidian cysts from gut walls of in- fected flounder embedded in pieces of clam were unsuc- cessful, so the life cycle is not known. Since fish become infected when only 50 mm in length when their diet con- sists of small invertebrates, a second intermediate host may be required in the parasite life cycle although no in- termediate host animals have yet been found for micro- sporidia. Another parasitic infection with metacercarial cyst of the trematode Stephanostomum baccatum has been studied by Wolfgang (1954a, b) in winter flounder from eastern Canada. He found that infection in inshore waters was greater near open water than on shoal grounds. Larger fish had heavier infections than small ones, the growth of the flounder was not impeded by heavy cyst infections, and no marked seasonal variation of the infection could be demonstrated. The life cycle of the parasite in eastern Canadian waters is as follows: mollusks, Buccinum undatum and Neptunea decemcostatum, primary intermediate hosts; six common pleuronectid species second intermediate hosts; Hemitripterus americanus and Hippoglossus com- mon definitive hosts. Experimental proof of relation- ships between S. baccatum adults in sea raven and the larvae in winter flounder was established. Experimental infections of winter flounder with S. baccatum cercariae dissected from infected snails was observed. The cer- cariae do not swim towards the flounder but wait until touched by the fish. They burrowed into a suitable site and encysted in muscle or connective tissue by secreting a hyaline cyst about themselves. Young-of-the-year flounders, seined in midsummer onshore and taken in surface tows near shore, were never infected. The smallest metamorphosed flounders (35 mm TL) were infected lightly at the end of August. Small fish (below 90 mm) taken during summer (age 0) date the earliest time at which a flounder may be infected. Because of the close nature of the association between hosts and the problems involved in eliminating any one of the hosts, control of the parasite is impractical. It does not slow the growth rate of flounder and does not harm man nor develop in him. Fish (1934) described a fungus disease of epidemic proportions in sea herring, Clupea harengus, and winter flounder throughout the Gulf of Maine. The causative agent was a species of fungus belonging to the genus Ichthyosporidium and the species was tentatively iden- tified as hoferi, first described in winter flounder by Ellis (1928). The organism is believed to be a normal parasite in herring, reaching epidemic proportions only when cer- tain unknown factors are operative. The epidemic, once initiated, increases in severity, reaches a peak, and sub- sides. Flounder may be an accidental host since infected flounder have been taken only in regions where large numbers of dead sea herring were available as food. Fish 11 I L934) believed the flounder acquired the infection by consumption of infected herring which acquire it by ingesting parasites liberated from fish in the same school; however, since winter flounder rarely eat fish and their mouths are too small to eat herring, this does not seem probable. It is more likely that scavenger organisms fed on the herring, after which flounder ate the scavengers, thus acquiring the parasites. The infection is believed to be established by way of the alimentary canal and spread throughout the host by the blood stream or lymphatics. There is no reason to believe this parasite capable o e infecting warm blooded animals. The complete life cycle of the organism is not known. The most common stage encountered in host tissues is the resting stage which appears as a spherical cell, com- posed of a heavy double wall enclosing the protoplast. Organisms ranged from 5 to 164.5 fj within which there appeared to be no difference in internal structure other than density of the cytoplasm and number of nucleii. From this stage (regardless of cell size), hyphal division may take place. The mycelium bores through surround- ing tissue and breaks up into a large number of daughter cells. The hyphal wall disintegrates and spores are liberated. Pathology — In flounder, internal lesions may occur in heart, liver, spleen, kidneys, intestinal tract, brain, and spinal chord. Macroscopic lesions appeared as white spherical firm masses or cysts. The viscera may be rid- dled with these from microscopic to bean-size cysts. In advanced lesions, firm cysts tended to disintegrate more pronouncedly in herring than in flounder. Micro- scopically, lesions were similar in all organs and hosts. An infiltration of mononuclear cells followed ingress of a single parasite. Tissue surrounding the parasite is replac- ed by an epithelioid type of tissue apparently derived from wandering monocytes. This was replaced even- tually by connective tissue believed to represent the host's chief defense mechanism to prevent spread of the parasite. As infection progresses, the parasites increased until the area once contained in the "tubercle" becomes a heterogeneous mass of parasites, infiltrating monocytes and epithelioid tissue, connective tissue, and necrotic debris. Mahoney et al. (1973) described a fin rot disease which reached epizootic proportions in 1967 in the New York Bight and has continued to occur annually. Winter floun- der were among the 22 principal species affected. The ex- ternal signs of disease were fin necrosis often accom- panied by skin hemorrhages, skin ulcers, and blindness. Bacteria of three genera, Aeromonas, Vibrio, and Pseudomonas were implicated as infective agents of dis- ease. Water pollution was thought to have a role in the disease as unsanitary conditions in aquaria are asso- ciated with similar epizootics, and the primary epizootic center is lower New York Harbor which is grossly polluted with sewage and industrial wastes. Infective bacteria are believed to be water borne. Disease incidence tended to parallel the seasonal regime of temperature increasing from low levels in spring, reaching highest levels from July to September, and de- creasing again in fall. Ziskowski and Murchelano (1975) reported the in- cidence of fin erosion in winter flounder from four areas: 1) New York Bight Apex, heavily polluted by dumping of sewage, sludge, and acid wastes; 2) ocean outside of the Bight, unpolluted; 3) Sandy Hook-Raritan Bays, domes- tic and industrial pollution impacted area; 4) Great Bay, N.J., relatively unpolluted. Results showed there was a significantly greater incidence of disease in the Bight Apex (371 or 14.1 r r of the fish affected) than outside the apex (36 or 1.9%). Smith (1935) described a hyperplastic epidermal dis- ease in winter flounder which resembles a papillomatous disease called "carp pox" that affects cyprinids in Euro- pean waters. The disease occurred in two specimens of winter flounder from Long Island Sound and was charac- terized by grayish white, irregular slightly elevated patches on the pigmented surface of the body. The his- tological characteristics of disease are a hyperplasia of epithelial cells without keratinization. The chorium is slightly edematous and thickened but without inflam- matory cells. In many places irregular, elongated, fibrous bands extend from the chorium into the epithelium. There is a rich capillary blood supply in diseased areas and in some areas large nucous cells and cells with eosinophilic granules appear. Both of these fish were also infested with the parasite Cryptocotyle lingua, a trematode occurring as larvae encysted in the fishes' skin. Transplantation of diseased tissue into four nor- mal flounders was not successful. The disease is probably benign as invasion of underlying structures and metastases were not present. There was no direct evidence that encysted larvae acted as a causative agent. Abnormalities — An abnormal variety of black bellied fish was reported by the Rhode Island Fish Commission for 1900 (Sherwood and Edwards 1901). Thirty-three per- cent of the flounder were ambicolored in 1898, 4% in 1900, and none by 1901. No reasons were given for this oc- currence. Abnormalities reported for winter flounder are presented in Table 7. 3.4 Nutrition and growth 3.41 Feeding Winter flounder are sight feeders. The importance of vision in juvenile feeding was studied by Pearcy (1962a). Fish fed in a dark room did not eat until zooplankton died and sank to the bottom. Field observations con- firmed that feeding occurs during the day. Stomachs emptied faster than indicated in laboratory experi- ments. Olla et al. (1969) also confirmed that winter flounder are sight feeders and active at day. At night they lie flat, heads resting on the bottom and eye turrets retracted, in a quiescent state. They assumed this state within 30 min after evening civil twilight and remained so until the beginning of morning civil sunrise. Relative volume of 12 Table 7. — Abnormalities in winter flounder. Table 8. — Food of winter flounder postlarvae to age I (Pearcy 1962a). Abnormality Remarks Source Albinism (partial) Reversal Tailless Ambicoloration (incomplete) (complete) Unpigmented spots on eyed side Dorsal wound Dorsal wound Abnormal squamation, loss of dorsal pterygiophores No hypural plate, only 26 vertebrae, probably result of accident No other abnormalities Left eye just over dorsal crest, hooked dorsal fin, abnormal branching of lateral line 4-13^ of 1959 year class from Georges Bank affected Breder(1938) Eisler(1963) Dawson (1962, 1967) Gudger(1935) Gudger(1945) Medcof(1946) Bishop (1946) MacPhee(1974)' Pearcy (1962c) Gudger(1934) Gudger(1934) Gudger(1934), Eisler(1963) Lux (1973) 'Unpublished data. gut contents showed day feeding. Samples taken between 0800 and 1300 contained food, samples at 0415 were empty indicating fish had not fed. Probable clearance time for the stomach is 7 to 11 h. Tyler (see footnote 5) reported on yearly feeding cycles of winter flounder in Passamaquoddy Bay. He found they had progressively more food in their stomachs after the first spring feeding in April when water temperature was between 3° and 4°C. The peak in quantity came at the end of May. Increased bottom temperatures during summer were accompanied by a decrease in stomach content volume. The lowest quantity was reached in November when some winter flounder ceased feeding. Water temperature at the onset of winter fasting had dropped to 5°-6°C from a peak of 10.1°C in September. Frame (1972) studied feeding habits and food of age I flounder in the Weweantic estuary, Mass. His findings were similar to Olla et al. (1969). He also found that the quantity of food consumed daily was variable. On cloudy days in summer, feeding may begin well after sunrise, so fish consume less. In winter, age I fish consumed less food, and their stomachs remained empty longer. 3.42 Food Sullivan (1915) stated that until yolk absorption, lar- vae did not eat. Larvae up to 3 wk ate only diatoms, a lit- tle later they ate small crustaceans. Pearcy (1962a) gave a detailed account of larval and young juvenile feeding habits. He also cited S. W. Richards' unpublished data that dinoflagellates were the most frequent food eaten by larvae from Long Island Sound. Young flounder from the Mystic River estuary, Conn., fed largely on invertebrates (Table 8). Empty stomachs were found in 72% postlarvae, 25% metamor- Postlarvae Metamorphos ng Juveniles Age I 3.4 mm Copepods Oopepods ( 'i ipepods Polvchaetes (Harpacticoid) Phytoplankton Nauplii Eun'temura Neanthes (pennate and Diaptnmus Cirratulus filamentous) Paracalanus Polychaetes Am phi pods Amphipods Harmothoe Protozoanlike Nemerteans Ampelisca organism Cnrophium Polvchaetes Invertebrate eggs Ostracods Maldanids Clymnella Neanthes Cirratulus Ampelisca Corophium 4-5 mm Nauplii 6-8 mm Polychaetes Larval and small phosing larvae, and 0.6% juveniles. Juveniles are eury- phagus. Seventy-seven organisms from seven phyla were identified. There was a high degree of selectivity at cer- tain times of the year. Comparisons of food of flounder inhabiting shores vs. deep water showed that the major groups of animals were the same but genera differed. The time required for juveniles fed in the laboratory to evacuate stomachs was determined by preserving in- dividuals at different times (Table 9). The rate of feed- ing of juveniles 22-55 mm during four intervals (water temperature 20°-22°C) was approximately 2.0-3.4% body weight/day. The results are questionable because of rapid growth of individuals during the summer in the wild, and daily feeding rate shown for other juveniles (Pearcv 1962a). Table 9. — Stomach evacuation time of juvenile winter flounder (Pearcy 1962a). Length of fish (mm) Water temp. CO Number of hours Half empty Empty 9-14 10-15 29-50 13-15 14-16 20.5-22 9 19 7-10 13.5-18 6-8 11-14 Tyler 7 described the digestive tract of winter flounder as follows: narrow buccal cavity and pharynx; incisor- like teeth on premaxillary and dentary; stomach without fundus; four large pyloric caecae distal to pyloric valve; intestines coiled in coelome (viewed from blind side), two complete clockwise coils followed by one complete coun- terclockwise, situated between first two coils; intestinal- rectal valve present. Relative length of parts of the alimentary tract (expressed as percent of total tract Tyler, A. V. 1973. Alimentary tract morphology of selected North Atlantic fishes in relation to food habits. Fish. Res. Board Can., Tech. Rep. 361, 23 p. 13 length) are: 6.3. lips to first gill cleft; 4.9, first gill cleft to stomach: 10.1, stomach length: 69.8, pyloric valve to in- testinal-rectal valve; 8.9. rectum length. Winter flounder cease to feed in winter, fasting from November to April (Tyler 1972b). Olla et al. (1969) ob- served feeding behavior of winter flounder in their natural habitat by means of scuba. While actively feed- ing, the flounder lies with head raised off the bottom and 12-17 rays of the dorsal fin braced vertically into the sub- strate. The left pelvic fin and several anal fin rays were used to support the head. In water currents of 20 cm/s the fish maintained its position by tucking the distal edges of the dorsal and anal fins into the bottom substrate. The eye turrets were extended and the eyes moved indepen- dently of one another. After sighting prey, the fish remained stationary pointed towards the prey, then lunged forward and downward covering about 10-15 cm to seize the prey. Mud, sand, and debris were expelled through the right branchial aperture. The fish then resumed the feeding position. If no food was sighted, the fish would swim to another location less than 1 m away and again resume feeding position. Adults — Throughout their range, winter flounder eat polychaete worms, amphipod and isopod crustaceans, pelecypods, and plant material. They are omnivorous and seem to be opportunistic, eating whatever is avail- able (Pearcy 1962a; Richards 1963; Mulkana 1966; MacPhee 1969; Frame 1972). Richards (1963) stated they ate a greater variety of food than any other demersal fish. Seasonal changes in the type of prey consumed were due partly to avail- ability of prey, and number and age of the predators. She also found that correlations between food diversity and total number of flounders were sometimes close, the highest numbers of flounders and number and varieties of amphipods, polychaetes, and molluscs occurring in spring and fall. Pearcy (1962a), Richards (1963), and Mulkana (1966) mentioned that with progressive increase in size, young winter flounder tend to prefer larger prey organisms. Frame (1972) compared species diversity in the stomach contents of age I winter flounder with contents of Petersen dredge hauls collected in the same area of the Weweantic estuary, Mass., from January to October. He used a modified percent overlap technique in an at- tempt to compare food utilization with prey diversity and availability. He found a low overlap value between dredge hauls and stomach contents in spring when the young flounder prefer planktonic copepods. By June the fish assumed a more benthic habit, and overlap values were higher. The value increased in July and October suggesting flounder adapt to a benthic existence by the midpoint of their first year. He proposed this dietary shift may be due to the animals' physiological require- ments rather than age alone. An example of this is that in spring, young flounder live at low salinities and tempera- tures which produce lower metabolic rates and conse- quently the fish uses less calories for metabolic mainten- ance; therefore, they survive on plankton. With increased temperatures and salinities later in the season, the meta- bolic rate increases requiring more calories. (See also section 3.44). Tyler (1972b) studied food resource division among northern marine fish predators in Passamaquoddy Bay. He showed that although over 100 prey species were in- cluded in stomachs of predators, each took only three or four principal species of prey which made up 70-99% of the mass of food for each predator. Winter flounder ate three principal species of polychaetes Nephtys, Lum- brinereis, and Praxillella. (See also section 4.6.) MacPhee (1969) showed that the most important category of food in the winter flounder's diet depends upon the type of bottom which the fish inhabits. The diet of flounder living on a predominantly rocky bottom is more variable than flounder living on a soft bottom. Frame (1972) agreed that winter flounder adapt their diet to environmental conditions. Fourteen phyla and 260 species have been found in winter flounder stomachs by a series of investigators (Table 10). 3.43 Growth rate Pearcy (1962a) gave comprehensive data on growth rates of age group flounder (Fig. 7). He pointed out there is a great deal of variation in average lengths within many months, which is partly due to difficulties in cal- culating a representative average length since prolonged spawning resulted in as much as 4 mo difference in age for a year class. Seasonal changes in growth were ap- parent. Growth is fast in spring and summer, slow in win- ter. Because metamorphosis of flounder was not com- pleted until June, the first 2 mo underestimated growth and were excluded from analysis. This decrease in stan- dard length often occurs during metamorphosis when caudal fin differentiation and body proportions change. Measurements of maximum length of otoliths of year class and maximum length of the opaque center com- pared with fish length at capture show that growth of the • 160- BEAM TRAWL YEAR -CLASS 1958 1959 • o i 140- OTTER TRAWL ■ D • / 9 120- A ■ 7 100- • 80- 60- ■ x^ • ■ • • 40- 20- A M 'j'j'a's'o 'n'd'j'f'm'a M J j'a'b'o n'd'j MONTH Figure 7.— Growth curve of juvenile winter flounder (from Pearcy 1962a). 14 Table 10.— Food organisms found in stomachs of winter flounder from different geographic areas. A. Long Island Sound (Richards 1963). B. Point Judith and Narrow River estuary, R.I. (Mulkana 1966). C. Mystic River, Conn. (Pearcy 1962a). D. Several— Cape Cod. Mass., to York, Maine (MacPhee 1969). E. Weweantic estuary, Mass. (Frame 1972). F. Conception Bay, Nova Scotia (Kennedy and Steele 1971). G. Bay of Fundy, Pas- samaquoddy Bay, N.B. (Wells et al. 1973). Organism Area Organism Area Chlorophyta Chaetomorplm linum Cladnphora serica Enteromorpha intestinalis Monostroma nxysperma Spongomorpha arcta I Iva lactuca Chrysophyta Diatoms Phaeophvta Ascophyllum nodosum Ectocarpus siliculosis Leathesia difformis P^'laiella littoralis Rhodophyta Acrosiphonia arcta Ahnfeltia plicata Asparagopsis hamifera Callithamnion byssoides Ceramium rubrum Chondrus crispus Corallina officinalis Dumontia incrassata Euthora cristata Polysiphonia lanosa Rhodymenia palmata Porifera Grantia sp. Coelenterata Diphasia fall ax Obelia enseralis Nemertinea Cephalothorax linearis Cerebratulus luridus Nematoda Annelida Oligochaeta Clitella arenarius (?) Enchytraeus albidus Polychaeta Ammotrypane acuta Ampharete acutifrons Amphicora fabricii Amphitrite johnstoni Antinoe sarsi Arabella tricolor Arenicola marina Aricidea fragilis Autolytus cornutus Capitella capitata Cirratulus cirratus Cistenides grandis C. gouldi Clymnella torquata Dodecaceria concharum Drilonereis elizabethae D. longa Eteone arctica E. longa E. trilineata Eudora truncata Eulalia uiridis Eumida sanguinea Eunoa nodosa Eupomatus dianthus Eusullis tubifex D Fabricia sabella G' Flabelligera affinis G' Glycera americana 1) G. dibranchiata 1) Goniada gracilis D Harmothoe extenuata H. imbricata A,D Lepidonotus squamatus L. variabilis D Lumbrinereis G' L. fragilis D L. tenuis G' Maldanopsis elongata Marphysa belli G' Megalona papillicornis h Neanthes caudata D N. succinea li N. uirens D Nephtys caeca 1) N. incisa I) N. picta I) Nereis ciliata D N. furcata I) TV. me gal ops D N. pelagica N. tenuis A,D N. uirens Nicolea zostericola B,D,G Ninoe nigripes G Ophelia radiata Pectinaria gouldi B,D Peloscolex benedeni A Phyllodoce fragilis <; P. groenlandica P. maculata Poly cirrus exemus A,B,D Polydora ligni A,D Potamilla neglecta Praxillella gracilis G P. praetermissa A Prionospio malmgreni A Pygiospio elegans G Scalabregma inflatum F,G Scolopus armiger B-E.G Spirorbis borealis F Sthenelais gracilis D,G Stylaroides arenosa B,D,G Syllis gracilis B,D Terrebelloides stroemi D Tharyx acuta A,C Sipunculoidea A,G Phaslosoma procerum D Mollusca D Amphineura D Ischnochiton ruber A Lepidochiton marmorea F Gastropoda D,G Acmea testudinalis F Anoba aculeas G Bitteum alternatum D,F,G Buccinium undatus B,D Cerastoderma pinnulatum D Crepidula fornicata A,C,E Crucibulum striatum F [)' A 2 A,E,G A A D A,C,D,G ' A D A,B,G A,G 3 ' E B I) A A.BJL A-E " A,B 6 A A,B,G 26 D A I) D A.D.F* D D,G,F ' ' D 3 G F E,F G 1 A,D I) IV A I) A,D A,G A.G B» A,B,G A A,D,F D,G A D A,F,G 2 G A,G I) F,G D,F A,D,G D E D K I> E 15 Table 10.— Continued. Organism Area Organism Area Hydrobia mi nut a Lacuna pallidula Littorina littorea L. palliata L. saxitilis Lunatia heros Sfargarites grnenlandica M. helicinus \felampus bidentatus Mitrella lunata Sassarius trivitatta Xatica pusilla Xeptunea decemcostatum Puncturella noachina Retusa canaliculata Sella adamsi Skenea planorbis Thais lapiltos Turbonilla interrupta Pelecypoda Anomia aculeata A. simplex Bivalve siphons Cerastoderma pinnulatum Clinoeardium ciliatum Crenella faba Cyrtopleura costata . Ensis directis Gemma gemma Haminea solitaria Hiatella arctica Laevicardium mortoni Lyonsia hyalina Macoma baltica M. tenta Mercenaria mercenaria Mesodesma arctata Modiolus modiolus Mulinia lateralis Mya arenana Mytilus edulis Nucula proximo N. tenuis Nymphen grassipes Saxicava arctica Serripes groenlandicus Siliqua costata Solemya borealis S. velum Tellina agilis Yoldia sapotilla Y limatula Arthropoda Crustacea Amphipoda Aeginella longicornis Ampelisca spinipes A. macrocephala Amphithoe longimana A- rubricata Anonyx nugax Ratea catherinsis Byblis serrata Calliopius laeuiusculus Caprella geometrica C. linearis Carinogammarus mucronatus Casco biglowi G 4 Corophium [volutator?) G C cylindricum D,G" C bonelli D Cymedusa filosa D Dexamine spinosa E,G Erichthonius brasiliensis D E difformis G Gammarus annulatus D G. lawrencianus E G. oceanicus A,D G. marinus A,E Grubia compta G Ischyrocerus anguipes G Jassa falcata E' J. marmorata A,E Lembos smithi D Leptochirus pinguis G Lysianopsis alba E Mclita dentata Mesometopa neglecta D Metopa pusilla 1) Metopila carinata E J Microdeutopus gryllotalpa F Monnculodes edwardsi F Orchomenella minuta F Photis reinhardi E Phoxocephalus holbolli A,F 2 Podocpropis nitida B,C Pontogeneia inermis C Stenothoe cypris F S. minuta F 2 Sympleustes glaber A,C Typhosa pinguis D,E,G' Unicola irrorata E U. leucopis E Cirripedia D Ralanus balannides D Cladocera A,E 2 Evadne nordmanni C,D,F,G" Podon leuckarti D,B" Copepoda B,D' Acartia sp. A,D,E Eurytemora sp. A Paracalanus sp. I) Pseudodiaptomus coronutus F Temora longicornis D Cumacea D Cyclaspis varians C,F Diastylis polita B,E' D. quadruspinosa 1) Oxyrostylis smithi E Isopoda Chiridotea caeca Clathura polita cyathura Edotea triloba A-D E. montosa D Erichsonella attenuata AD' Idotea baltica D I metallica D,G' I phosphorea D I. viridis C ■Jaera albifrons CD J. marina C,D S Leptochelia savignyi C Ostracoda A,D Cylindroleberis mariae B-D Pontocypris edwardsi G Pscudocytheretta edwardsi A,D,G !1 C F' B,C F,G* A D B-D F,G' A,D,F,G" D D D,P D.G D J B-D« A,C,D,F,G' CD D.G F C 5 F B,C 5 A,F F* A A.C.D.G " A 2 D,F A A F D A-D.G F A,C,F,G C C A,B C 5 C A,C A,B,E,F AC D A A-C B,G A C 6 A-CG 6 D D 3 D D B G D B-D" B,C» B,C C 16 Table 10.— Continued. Organism Area Organism Area Sarsiella americana Sarsiella zostericola Decapoda Cancer irroratus Crangon septimspinosus Neomysis americana Neopanope texana sayi Pagurus longicarpus Palaemonites vulgaris Polyonyx machrocheles Sabinea sarsii Upogebia affinis Insecta Insect larvae Invertebrate eggs Echinodermata Asteroidea B,C" Asterias forbesi A,C A. vulgaris Echinoidea F Arbacia punctulata A-C 7 Strongylocen tratus droh bach iensis A,C 25 Holothuroidea B Cucumaria frondosa A.D-F Ophiuroidea C Amphiphnlis xquamata B Ophiophalia aculeata A Chordata A Molgula manhattensis Didemnum candidum A.D-F Pisces B,D Fish remains Fish eggs D,F D D D,F,G D,G C-E I) CD G F D,F< 'Wells et al. (1973) by percent weight. 'Richards (1963) by occurrence and percent volume. 'MaePhee (1969) numbers and occurrence. 'Kennedy and Steele (1971) numbers plus volume. 'Pearcy (1962a) by volume. 'Mulkana (1966) by mean number/stomach and percent frequency occurrence. Frame (1972) numbers and occurrence. otolith after deposition of the opaque center was variable, and therefore exact age within the group can- not be determined by otolith characteristics. No cal- cified otoliths were found in fresh specimens until the left eye was in the median position (7.0 mm or greater). Growth in weight was calculated by Pearcy (1962a) from average length of flounder in millimeters at the beginning of each month converted to weight in grams by the formula: W = 0.000017L 3 (Fig. 8). AVERAGE WEIGHT INSTANTANEOUS GROWTH RATE I , ' . I o I „ I .. I „ I l .IJ, l , l . l .l Jl J J A s ON DJFMAMJ JASON J F Figure 8. — Average monthly weight gain in the Mystic River estuary in winter flounder (from Pearcy 1962a). phosis at 2°, 5°, and 8°C. The fish were reared in all black 38-liter aquaria at a stocking density of ap- proximately 13/liter. The aquaria were semiclosed and aerated. Salinity varied between 28 and 30% . Larvae were fed wild zooplankton (principally copepod nauplii at concentrations of 2,000/liter). Growth was measured weekly. Specific daily growth was calculated from the formula SG 100 log e WT -log e wt T * 1 o where SG WT (S> wt specific growth dry weight at the end of the time interval dry weight at the beginning of the time interval T = time in days. Temperature strongly influenced growth of larvae and juveniles, growth being directly related to temperature. Regression analysis of the semilog arithmetic transfor- mation of growth on time gave the following linear equations: The instantaneous rates of growth {k = dw/dt) were calculated from relative growth by means of the for- mulas: b = (Wo i + 1 -Woi)/Woi where: Wo= average individual weight at beginning of month i b = relative growth and e k = 6 + 1. Laurence (1975) studied growth of laboratory reared winter flounder larvae from hatching through metamor- 8°C: Log Y = 0.755 + 0.358X r = 0.99 5°C: Log 7 = 0.840 + 0.213X r = 0.97 2°C: Log y = 0.840 + 0.110X r = 0.85. Growth rate was significantly greater at 8°C than at 5°C, and greater at 5°C than at 2°C, but not significantly so. Larvae held at 2°C died before completing metamor- phosis. Time to metamorphosis was 49 days at 8°C and 80 days at 5°C. Daily specific growth was greater at higher temperatures and was highly variable from week to week. Mean specific growth rates were 10.1%/day at 8°C, 5.8%/day at 5°C, and 2.6%/day at 2°C. 17 Adults — Several authors have calculated growth rates of adults (Fig. 9). Kennedy and Steele (1971) calculated the age of Long Pond. Newfoundland, flounder from otoliths. They found no difference between growth curves o\ males and females until age IX when the females were much larger. This could be due to low numbers of females involved, or failure to age the fish correctly. The regression equations for the fish were: Females: Log W = 3.1441 log L - 2.0702 Males: Log W = 2.9833 log L - 1.9041 with L in centimeters and W in grams. Berry et al. (1965) determined age from otoliths and scales of winter flounder in Rhode Island. They found that scale markings were unreliable for making age determinations, and that otoliths provide fully reliable estimates only to age III, which agrees with Landers (1941). Their growth equations, based on the Walford plot, are: Females: / f+J = 395.7(0.34) + 0.66/, Males: / t+ , = 323.1(0.42) + 0.58/, where l t = length in millimeters at time t. They concluded a typical growth curve for winter flounder could not be developed because the species con- sisted of discrete stocks which were subject to variable rates of exploitation and environmental conditions; and that females grew faster than males. Poole (1966b) studied growth rates offish collected in several south shore bays of Long Island. He used otoliths and agreed with Berry's (1959) description of opaque band formation where the first opaque band useful for judging age appears in October and continues its growth to July when the fish is several months beyond age group I. Poole found that females grew faster than males and that the growth rate was different in certain bays. Lux (1973) calculated age and growth of winter floun- der on Georges Bank by means of scale analysis. Direct proportion growth calculations were made using the equation: L n = C + SJS[L - C] where L n = fish length (TL) at time of formation of nth annulus C = fish TL at scale formation S n = anterior scale radius to nth annulus S = anterior scale radius at capture L = fish TL at capture. He found growth was more rapid on Georges Bank than on inshore areas, fish from eastern Georges Bank grow- ing slightly faster than those from the western part. Females grew faster than males after age II. Growth equations were: It /°°(1 -exp[-K(t-t )}) where It = length in centimeters / oo = theoretical maximum length K = rate of change in length increment to = age at which growth in length theoreti- cally begins Male: It = 550 (1 - exp [0.37 ( t + 0.05) ] ) Female: It = 630 (1 - exp [0.31 (t - 0.05)]) where It = length at age t. Howe and Coates (1975) described growth of winter flounder off the Massachusetts coast. They plotted "Walford lines": y = a + bx L, = (x) — length in millimeters at time t NEWFOUNDLAND NARRAGANSETT BAY WESTERN GEORGES BANK EASTERN GEORGES BANK GEORGES BANK NORTH OF CAPE COD SOUTH 8 EAST OF CAPE COO YEARS Figure 9. — Growth curves of adult winter flounders (from Saila et al. 1965; Poole 1966a; Kennedy and Steele 1971; Lux 1973; and Howe and Coates 1975). 18 L co = a — theoretical maximum length v = growth/month in millimeters b = rate of change in growth. There were significant growth differences between geo- graphic areas. The growth rates of females (F) south of Cape Cod were greater than those north of Cape Cod but less than those from Georges Bank. Males (M) grew faster on Georges Bank than south of Cape Cod. Females grew more rapidly than males south of Cape Cod but not on Georges Bank. The growth equations calculated for the fish are as follows: Ford -Waif or d Growth Equation L t+1 = 455.38(1 - 0.69) + 0.69L, L,+i = 476.76 (1 - 0.78) + 0.78L, L t+i = 487.38 (1 - 0.71) + 0.71L , Lt+i = 534.40 (1 - 0.69) + 0.69L, Lt+i = 622.38 (1 - 0.64) + 0.64L, Area Sex North of F Cape Cod East and M south of F Cape Cod Georges M Bank F where L = lc t ti length in millimeters = time in years. 3.44 Metabolism Laurence (1975) studied metabolism of laboratory- reared larvae and juveniles. He used Warburg respirom- eters to measure oxygen consumption for 2-h periods. Absolute values of larval oxygen consumption increased until metamorphosis, at which time they declined. After metamorphosis, oxygen consumption again increased. Temperature directly affected oxygen consumption with higher consumption at higher temperatures. Metabolic rate on a unit weight basis decreased with increasing size from hatching through metamorphosis. Absolute values of routine metabolism expressed in liters of oxygen con- sumed, regressed on body weight were best described by a third degree polynomial. 'W 'W 'W The metabolic rate of fish with respect to weight is usually described by the linearly related log transfor- mation log 10 oxygen consumption = a + b logioweight in which the slope value is approximately 0.80. Although larval winter flounder conformed to this type of relationship, metamorphosed juveniles did not. There- fore, continuous metabolism of this fish must be describ- ed by a different analysis than standard log-log transfor- mation. This change in metabolic patterns probably reflects changes in body shape and activity patterns oc- 2°C: O > = 0.451 + 6.0 X 10 + 1.5 X 10" 1( W 3 W- 1.1 X 10 5°C: 02 = 0.601 + 3.3 X 10" + 2.5 X \0~ W W V- 1.7 x 10 8°C: 2 = 0.379 + 6.8 X 10" + 7.6 X 10~ 10 W 3 A w- 4.3 X 10 curring at metamorphosis, and perhaps reflects phy- siological changes in the respiratory system. Salinity ef- fects were not examined. Frame (1973a) studied oxygen uptake rates of young winter flounder from the Weweantic River estuary, Mass., to determine the effects of estuarine conditions (salinity and temperature differences) on respiration and metabolic rates. He found that the quantity of O2 up- take (ml Q 2 /h per g) as a function of increased tempera- ture did not differ significantly between salinities of 10- 20% o but is 40-50% higher at 30% c . Metabolic rates per gram did not differ between fish sizes used (10.0-13.5 cm TL and 14.0-17.5 cm TL) or between sexes. Two fac- tors, temperature and weight, were necessary for calcula- tion of a fish's energy expenditure under routine metabol- ~"Kj ° i5 o e 10 o Y=-O.I78 + 0I5X CONFIDENCE LIMITS 16 20 24 TEMPERATURE (°C) Figure 10. — Oxygen consumption (Y) of winter flounder at different temperatures and salinities and effect of weight (X) (from Frame 1973a). ic conditions (Fig. 10). The expression for the equations in Figure 10 is: y = oxygen (ml 2 /h per g) X = temperature (°C) This is based on the assumption that 1.0 ml 2 is equiva- lent to 5.0 calories. Adjustment of the metabolic level by immature fish indicates the euryhaline nature of this species and suggests a physiological reason why young flounder are found in estuaries. Voyer and Morrison (1972) studied respiration of win- ter flounder at different temperatures and oxygen con- centrations. They found the average rate of oxygen con- sumed by flounder at 10° C was 35 and 55 mg (0 2 /kg body weight per hour at 3.5 and 8.6 mg dissolved oxygen (DO)/liter, respectively, (x fish weights 18.0-24.39 g for high 2 and 13.0-22.64 g for low 2 .) At 20°C the aver- age rate of 2 uptake was 70 at 8.2 mg DO/1 and 97 at 6.3 mg DO/1. Oxygen consumption rates were signifi- cantly greater at 20°C than 10°C. In two of three ex- periments, rates of oxygen uptake were lower among groups of flounder maintained at reduced dissolved oxy- gen concentrations for 15-25 h. No dissolved oxygen-tem- perature interactions were apparent. 19 Huntsman and Sparks (1924) studied the effect of 9ize on respiratory rate which they measured by counting opercular movements per minute (Table 11). As the size of the fish increased, the respiratory rate decreased; the maximum movements showed the most regular decrease with increase in size. Table 11. — Effect of size on respiratory rate (opercular movements/minute) of winter floun- der (from Huntsman and Sparks 1924). Size (mm) Initial M iximum Final 100 141 191 130 1 50 100 135 103 200 76 109 51 250 86 93 61 300 73 81 53 Horton et al. 8 determined oxygen consumption to be 42.15 mg Q 2 /kg body weight per hour at a mean tem- perature of 13.4°C and salinity 30°/oo for mean body weight of 852 g. Frame (1973b) measured food intake and conversion efficiency for age I winter flounder under different tem- peratures and salinities. He defined conversion ef- ficiency as increase in the weight of a fish divided by the weight of food ingested for a given period of time. Only fish held at 12°C and 16°C in 20%>o salinity had a nor- mal growth rate. Conversion effiency ranged from 13.9 to 19.0%. The regression equation relating daily growth in average body weight (Y) to daily ration/average body weight (X) was Y = 1.651 + 1.832X. Temperature rather than salinity appears to have caused stress con- ditions although metabolic factors such as lipid syn- thesis and protein loss may have masked the effect of salinity. Frame proposed flounder survival may be con- trolled by their ability to move gradually into favorable temperature-salinity environments. Unseasonal tem- perature-salinity regimes imposed on age I flounder may be fatal. Endocrine system and hormones — Phillips and Mul- row (1959) found that winter flounder corpuscles of Stan- nius, previously thought to be analagous to the adrenal cortex, were not concerned with the production of adrenocorticosteroids. They did not, however, suggest what the function of the corpuscles of Stannius might be. Grafflin (1935) studied kidney concentration of urea and urine flow in winter flounder. The highest urine plasma ratios fall in the lower range of urine flow (urea plasma milligrams percent in plasma x 12.0, range 8.5- 18.4; in urine x 16.0, range 10.9-25.9; renal urine/plasma ratios x 1.3. range 1.0-1.8; urine flow cmVkg per 24 h x 23.0, range 8.3-45.6). Considerable variation occurred in chloride concentration (0-87 millimoles/liter) and the ac- tual rate of urine flow. Grafflin concluded there was no 'Horton. D. B., D. W. Bridges, and J. J. Cech, Jr. 1973. The de- velopment of biomedical procedures for establishing water quality criteria of marine fish. First Annu. Rep. to Environ. Prot. Agency, Contract R-80031, 48 p. direct relationship between rate of urine flow and urinary chloride concentration. Grafflin and Gould (1936) found that approximately one-half the normal total nitrogen of winter flounder urine could not be accounted for by ordinary nitrog- enous constituents. Percent of total nitrogen (N) (43.4 mg N/100 cm 1 urine) of urine = urea 21.2%, ammonia N 1.8%, uric acid 1.2%, total creatinine N 15%, amino acid N 4.2%, and undetermined 51.1%. Trimethylamine oxide was absent or present in very small concentrations in the urine. Maack and Kinter (1969) reported the first quan- titative evidence for transport of intact filtered proteins across the kidney tubules. Morphological observations obtained by Bulger and Frump" suggest that intact pro- tein is first transported across the brush border into the cell, from there to the intercellular spaces, and finally across the basement membrane to the peritubular space. Maack and Kinter (1969) speculated that transtubular transport of intact protein was the primary mechanism for handling normal protein loads, catabolism only oc- curring when an overload of protein is presented to the renal tubules. Kleinzeller and McAvoy (1973) conducted studies on the transport systems for sugars at the peritubular face of the renal tubular cells to obtain information on the reab- sorptive process using various sugars as inhibitors. A three carrier mediated pathway of sugar transport at the antiluminal cell face of the flounder renal tubule seemed to be operating: the pathway of the nonmetabolizable a methyl D-galactoside (not shared by D-glucose); the pathway shared by D-galactose and D-glucose; the path- way shared by the D-galactose and 2-deoxy-D-galactose. Ammonia is the primary nitrogenous excretory product in teleosts. For the most part, ammonia is produced from precursers in the liver, transported by the blood to the gills, and excreted by diffusion (Janicki and Lingis 1970). Liver homogenates from winter flounder produce ammonia from L-aspartate and L-glutamate at the rate of 2.7 ± 0.8 M moles NH/g tissue wet weight per hour at 25°C for the former and 10.0 ± 0.9 V- moles NH : ,/g tissue wet weight per hour at 25°C for the latter. Mito- chondrial and cytoplasmic fractions combined, produced ammonia from L-aspartate but single nuclear mitochon- drial and cytoplasmic fractions did not. Results are con- sistent with a general scheme in which the amino group of L-aspartate undergoes transamination with a keto- glutarate to form L-glutamate by action of L-aspartate aminotransferase, and ammonia is liberated from L- glutamic acid by L-glutamic acid dehydrogenase. How- ever, it is not clear which transaminase is involved. Goldstein and Forster (1965) studied urea production in winter flounder. Although teleosts are considered am- moniotelic, teleost blood contains significant quan- tities of urea (the origin of which is unknown since the complete cycle for synthesizing urea is not present in liv- ing teleost fishes). Activity of the uricolytic pathway "Bulger and Frump. Pers. commun., mentioned in Maack and Kinter 1969. 20 (uric acid-urea) was assayed in slices from winter floun- der livers. The rate of conversion of uric acid to urea was 23 ji moles urea/g per hour. Allantoin and allantoic acid were also converted to urea at the same rate. Uric acid could be converted to urea by a three step process: urate -allantoin-allantoicicate^urea. Purines are, therefore, a source of urea in fishes. Hormones — Donahue (1941) tested extracts of winter flounder ovaries for their estrogenic properties and found that the extracts contained estrogen but in quantities less than one standard rat unit. This might be useful for comparison to mammals but it is not clear how this relates to fish. 3.45 Physiology Pesch (1970) studied the electrophoretic profiles of plasma protein (thought to be reliable indicators of phys- iological well being). Variations are related to changes in the body's metabolic requirements, defense against in- vasion and injury, maintenance of body pH, osmotic pressure, and regulation of cellular activity and func- tion. Plasma protein concentration in flounder was 3-4 g/100 ml of plasma, the slow and medium group being most prominent. In both sexes the concentration of individual fractions differed according to stage of gonad matura- tion. Total concentration was greater in mature than in immature fish. In females, the slow fraction was respon- sible for the increase and was due to addition of vitellin which forms yolk protein. In males, the fast fraction was responsible for the increase, which could be due to the transport property of the fast fraction or it could be serv- ing as a source of amino acids. An immature male with tail rot had low plasma protein concentrations of about one-half normal. Aging is associated with increased plasma protein concentration, especially of slow and Table 12. — Blood chemistry values for winter flounder. Component Values Miscellaneous Source Plasma chloride Plasma protein Erythrocyte content Hemoglobin Freezing point depression Serum osmolality' (mOsm/1) Serum sodium (mmoles/1) Serum chloride (mmoles/1) Serum potassium (mmoles/1) Serum protein (g/100 ml) Erythrocytes (X 107mm 3 ) Hematocrit (%) Hemoglobin (g/100 ml) 149.7-158.4 mOsm/1 x = 154.2 mOsm/1 3-4g/100ml 235-372 mmYlO' x = 294 mm 3 6.16-10.44 g/100 ml x = 8.93 g/100 ml Summer x = -0.63°C 405.0 ± 7.0(12) 185.8 ± 3.6 (12) 157.9 ± 1.3(12) 5.2 ± 0.3(12) 5.5 ±0.3(12) 2.25 ± 0.19(12) 22.3 ± 1.6 (12) 8.44 ± 0.16(12) Winter i = -1.15°C 2 426.0± 6.0 (9) 185.4 ± 4.5 (9) 152.0 ± 3.5 (9) 2 4.0 ± 0.2 (9) 3 3.1 ± 0.2 (10) 2.01 ± 0.10(10) 22.9 ± 1.2 (10) 3 5.1 ±0.40(10) Mean length offish 203 mm Grafflin(1935) Pesch (1970) Eislerf 1965a) Pearcy (1961) Umminger and Mahoney (1972) Freezing point (°C) Melting point (°C) Melting point- freezing point (°C) Sodium (mMl ) Chloride (mMI -1 ) % due to NaCl Dialysed Serum serum -1.37 ±0.31? -0.65 -0.69 ± 0.07 — -0.75 ± 0.03 -0.01 -0.67 ± 0.07 — 0.62 ± 0.35 0.64 0.02 ± 0.001 — 250 ± 12 — 194 ± 6 — 178 ± 6 0.0 147 ± 14 — 58.1 — 94.0 — Dialysate -0.72 -0.70 0.02 172 March (watertemp. -1.2°C, Duman and total no. fish 12) De Vries (1974) August (water temp. +17°C, total no. fish 8) March August March August March August March August March August 21 Table 12.— Continued. Component Values Miscellaneous Source Confidence Number Mean limits used 86 iSLof fish 24.7 ± 1.1(98) Red blood cell count 1.81 X 107mm' ± 0.13 Hortonet al. Hemoglobin 5.5 g^ ± 0.4 91 Total value (1973)' concentration Hematocrit 19% ± 2 92 Total value Thrombocyte count 135.5X 107mm 3 ±26.6 26 Total value Erythrocytic 1.4cm/h ± 0.3 59 Total value sedimentation Corpuscular 112JU 3 ±13 88 Mean value volume (RBC) Corpuscular hemoglobin 34 picograms ± 3 88 Mean value Corpuscular hemoglobin 31 g% ± 2 91 Mean value concentration White blood cell count 40.8X 107mm 3 ± 5.4 82 Total % of WBC Lymphocytes 51% ± 4 92 Total % of WBC Thrombocyte 39^ ± 3 92 Total % of WBC Neutrophil 9% ± 2 92 Total % of WBC Basophil <1% istown Pond Narragansett Bay Poole (1966b) 1 .mil; Nland ba\- Dickie and McCracken (1955) St. Marys Bay, N.S. 1948-53 Kennedy and Steele (1971) Newfoundland Age Great South Moriches Shinne- cock Peconic Nov. Dec. Mar. Apr. May- June July Sept.- Oct. I 1 56 89 3 1 2 11 15 7.8 159 199 29 50 22 26 1% III ;>3 236 211 316 126 69 98 54 42 5% 6% 4% rv 100 241 171 312 82 77 99 86 110 18% 18% 12% 17% 2% V 45 82 110 128 17 35 38 62 137 19% 45% 20% 25% 16% VI 16 25 25 37 5 7 3 11 136 22% 28% 2% 12% 23% 22% \1I 4 7 13 27 1 2 103 17% 5% 10% 23% 4% 18% \tti 1 5 1 12 68 15% 2% 10% 13% 4% 23% IX X 12(9+) 8(9+1) 14 26 41 14 14% 2% 45% 30% 5% 15% 4% 5% 12% 1% \ 14 2% £(76) 3% (35) (27) 6% 1% (179) (49) 1% (66) NANTUCKET SHOALS WATCH HILL POINT JUDITH UJ O or LlI Cl AUG 1927 OTTER TRAWL N = 200 MAR-AUG 1941 OTTER TRAWL N=2775 NANTUCKET SOUND SEPT 1941 OTTER TRAWL N= 156 4 - OCT -NOV 1941 OTTER TRAWL N=283 APR -MAY 1942 OTTER TRAWL N = 235 -r- 20 25 30 35 40 45 50 55 CENTIMETERS 20 25 30 35 40 45 50 20 25 30 35 40 45 CENTIMETERS Figure 12.— Size composition of winter flounder from Nantucket Shoals, Watch Hill, and Point Judith, R.I. Data smoothed by moving average of threes (from Perlmutter 1947). dense; therefore, interested readers should consult the original reference. Other work has been done by Perl- mutter (1947) (Fig. 12), de Sylva et al. (see footnote 3), Lux (1969), Tyler (1972a), and Kennedy and Steele (1971) (Fig. 13). Changes in length composition with depth were calculated by McCracken (1963) and are also discussed under sections 2.2, 2.3, and 3.1 (Fig. 14). 4.2 Abundance and density 4.21 Average abundance The results of authors who estimated average abun- dance of winter flounder are summarized in Table 18. 26 40 -i AUGUST 20-24 OCT 20 AND NOV 10 NOV." DEC. (77) i — r — i — i — i ' i *r MARCH (36) UJ < uj o UJ o_ SEPT.- OCT (67) o-"Vr — rh — i — i — r CD 00 — CM 00 C\J C\J i i O CD C\J C\J rO i O i CO 00 ro ro CD i LENGTH - CM Figure 13. — Size composition of winter flounder from Newfoundland (from Kennedy and Steele 1971). Oviatt and Nixon (1973) determined by multiple regression analyses of fish numbers and biomass on 14 environmental variables that only temperature and depth were factors influencing winter flounder abun- A BCD 10 FATHOMS 60^ 40- 20- A B C D A B C D A B C D A B C D SIZE GROUPS Figure 14. — Changes in length composition with depth of winter flounder in Northumberland Strait. Size groups are: A = 10-19 cm; B = 20-24 cm; C = 25-29 cm; and D = 30 cm and over. (From Mc- Cracken 1963.) dance. This is a reflection of tendency for fish to move out of the shallow waters as temperature warms in sum- mer and back in as the water cools in winter. Jeffries and Johnson (1974) reported on 7-yr variations in winter flounder abundance in Narragansett Bay. The relative abundance appeared to be associated with climatic trends but not with fishing pressure, but the an- nual abundance in the bay is reflected 2 to 3 yr later in the commercial catch. A major reduction in abundance of winter flounder was statistically related to a seemingly insignificant trend of temperature increase. Increased average temperatures in April were associated with a decrease in future catch, the 2- to 3-yr lag being almost equal to the period required for flounder to grow from lar- vae to catchable size. Jeffries and Johnson (1974) sug- gested that the chief effect of the temperature increase might be to hasten metamorphosis which takes place in April. This would cause the flounder to leave the plank- ton earlier and thereby encounter a set of predators qualitatively or quantitatively different from those ex- perienced by juvenile flounders of previous years. When a small change in the physical environment occurs over a period of several generations there is a much greater set of consequences resulting than would be predicted from physiological tolerances of each species involved. 27 Table 18.— Average density estimates of winter flounder. Life Area stage Density estimate Author Narragansett Bay Larvae 0,0068/m 1 Herman (1963) Long Pond, Adults 14.9catch/man-h Kennedy and Steele Newfoundland (1971) Narragansett Bay Larvae x = 54.09/100 m 1 Range (11. 1-107.1) Marine Res. Inc. (1974)' Mystic River, Adults Mar. 153/ha 15,300/km' Haedrich and Boston. Mass. June 37/ha Aug. 180/ha 300/km ! 18,000/km 1 Haedrich(1974) Nov. 368/ha 36,800/km ! „ Delaware, Adults 241.776 Radle(1971) Indian River Cape Cod Canal Eggs Mar.-l June 0.450/m J Fairbanks et al. Larvae Mar. -May 0.035/m 1 (1971) Buzzards Bay Eggs Feb. -May 0.074/m 3 Larvae Mar. -June 0.113/m 3 'Marine Research Inc. 1974. 19th Rome Point Investigations, Narragansett Bay Ichthyoplankton Survey Final Report to the Narragansett Electric Company. Smelt Alewife Flounder Figure 15.— Annual cycle of fish biomass in Mystic River, Mass. (from Haedrich and Haedrich 1974). 4.22 Changes in abundance 4.23 Density Seasonal abundance varies for reasons discussed in sections 2.2, 2.3, and 3.5. Greatest density of eggs occurs in February and March, of larvae in April and May, and of adults in win- ter and spring (Table 18). 28 4.24 Changes in density Haedrich and Haedrich (1974) (Fig. 15), Oviatt and Nixon (1973) (Fig. 16) and Pearcy (1962a) (Fig. 17) cal- culated seasonal changes in density of flounder popula- tions in the Mystic River, Mass., Narragansett Bay, and Mystic River, Conn., respectively. 75 50 25 k 250- 200 150 100 50 (a) Winter flounder 1971 iyr<; i»n -r 1972 trtirtiiz 1971 /T^-S> Figure 16.— Biomass and numbers of winter flounder in Narragan- sett Bay (from Oviatt and Nixon 1973). 4.3 Natality and recruitment 4.31 Reproduction rates See section 3.1. Survival rates — Figure 18 is a survival curve for larval and juvenile winter flounder from Pearcy (1962a). 4.32 Factors affecting reproduction Tyler and Dunn (1976) studied growth and measures of somatic and organ condition in relation to meal frequen- cy. Six ration levels were established by feeding fish a mixed diet of whole chopped clams and beef liver cubes at the following frequencies: one meal per day, one meal every other day, every 4th day, every 8th day, every 16th day, no food. The testing period was July through December. Food was supplied in excess of quantities eaten at each meal, water temperature was 7°C. Decrease in feeding frequencies resulted in increase in food consumption per meal but less food consumption per month. At two meals per month, fish did not eat more per meal. The maintenance ration was 7.9 cal/g per day. Weight loss during starvation equalled 2.14-2.05 g cal/g per day. Gross conversion efficiency ranged from 1 to 16°r and was positively correlated with ration. Net conversion ef- ficiency averaged 24.3°c and was not related to ration. Condition, liver weight, percent fat in the liver, and per- cent ovarian follicles with yolk were positively cor- Figure 17. -Average density of flounder in Mystic River, Conn, (from Pearcy 1962a). 5- 4 - rr Id DD 5 z o O 2 - NUMBER LOG NUMBER Figure 18. — Survival curve for larval and juvenile winter flounder. Mystic River estuary. Conn, (from Pearcy 1962a). 29 related with mean calories consumed per day. The smaller proportion of oocytes with yolk in fish with decreased rations was due to the decrease in the num- bers of oocytes starting vitellogenesis. The field popula- tion from Passamoquoddy Bay, N.B., showed the same negative correlation between condition index and per- cent oocytes not undergoing vitellogenesis. This in- dicated that field fish were not getting all the food they could use. and the adaptive reproductive strategy in the face of the lack of food was to sacrifice egg production and maintain body weight so that when a good year came their bodies would be large and able to carry a large ovary. 4.33 Recruitment Age or length at which flounders are recruited into the fishery varies. Briggs (1965) calculated sports fishery recruitment at 200 mm TL for South Shore bays, Long Island, and 260 mm TL for Gardeners and Peconic Bays. Dickie and McCracken (1955) gave commercial fishery data for St. Marys Bay, Nova Scotia, 3-4 yr, 363 g. Perl- mutter (1947) reported commercial and sport data for Long Island and New York. 180-200 mm, and Watch Hill and Point Judith, R.I., 170-220 mm. Saila et al. (1965) gave commercial data for Narragansett Bay and off- shore waters in Rhode Island: 18 mo (first entry) age III fully recruited and 250 mm. Factors influencing recruit- ment were size selection by fishermen, differences in depth distribution with age, mesh size of fishing net, and market preferences. See also section 4.5. 4.4 Mortality and morbidity 4.41 Mortality rates Pearcy (1962a) estimated loss rate for small larvae in a Connecticut estuary as 20%/day compared with 4%/day for postlarvae. Juvenile mortality rates were 0.31/mo for age and 0.084/mo for age I. Total mortality during lar- val and juvenile stages is approximately 99.98-99.99% (Table 19). A summary of mortality rate values for adult winter flounder calculated by several authors is presented in Table 20. Table 19.— Provisional life table for larval and juvenile stages of winter flounder (from Pearcy 1962a). Age Sur- Numbers Mortality in months vivors dying rate X 100 Larvae 0.7- 1.5 100,000 97,459 97.46 1.5- 2.4 2,541 1,099 43.25 Juveniles 2.4-12.4 1,442 1,398 96.95 12.4-22.4 44 26 59.09 22.4- 18 99.982 4.42 Factors causing or affecting mortality Pearcy (1962a) found that the most important factors affecting mortality of larvae were translocation and natural mortality. Translocation out of the estuary by seaward drift was significant and though little is known of the fate of these larvae, conditions were surmised to be more unfavorable offshore for larvae because of lack of suitable food. Predation was also thought to be the major cause of juvenile and larval mortality. There was no in- dication of accelerated mortality during the period of metamorphosis for the winter flounder (see Table 19) as mortality rates on a percentage basis were about the same. Mortality rates decreased with age. The average monthly survival rate for age group was about 69%; for age group I it was 92% (Fig. 18). Dickie and McCracken (1955) found that the leading cause of natural mortality of adult flounder in Pas- samaquoddy Bay was predation. The winter period was the most dangerous as 30% of the mortality occurred from November to April. Table 20. — Summary of mortality rate data of winter flounder. Natural Total mortality' Fishing annual rate mortality mortality Geographic location Year Source 0.54 0.24 0.78 Long Island Sound & bays 1937 Perlmutter (1947) 0.33 0.43 0.76 Long Island Sound & bays Figures calculated by Poole (instantaneous rate) 0.321 0.475 St. Marys Bay, Nova Scotia 1949-50 Dickie and Mc- Cracken (1955) 0.296 0.272 Males Females St. Marys Bay, Nova Scotia 1952-53 0.56 0.65 Charlestown Pond, R.I. Saila etal. (1965) 0.51 0.58 Narragansett Bay H.Vi 0.22 0.72 Great South Bay, N.Y. 1964 Poole (1969) 0.52 0.21 0.73 Great South Bay, N.Y. 1965 0.52 0.20 (instantaneous ra 0.72 te) Great South Bay, N.Y. 1966 0.273 0.271 0.474 South of Cape Cod 1964-66 Howe and Coates (1975) 30 4.5 Dynamics of the population as a whole Dickie and McCracken (1955) analyzed a population of winter flounder in St. Marys Bay, western Nova Scotia, where a commercial flounder fishery began in 1948. This fishery showed a rapid rise in landings, a subsequent drop, and a stabilization as the catch appeared to reach a state of balance with production. Formulas used to cal- culate yield isopleth diagrams are: Growth W t _ t = W°°(l - exp[-k (* - t )] 3 where W = weight in pounds W°° = upper asymptote of growth curve (2.43) k = slope (0.40) t = any age in years 1 = time when length theoretically is 0. Values obtained W t _ t =2.38 (1 - exp[ -0.39U - t ))) 3 . Initial population size p=y/ M where P = population size Y = catch (weight in pounds) M = rate of exploitation. Yield equation pnII7 r ,, ,. . > -i ^&nexp[- nK(t - L)} Y„, = FRW<*> exp[-M (t n -t„ )]£ ^ p p ,.= o F+M+nK . (l - exp[-(F + M+nK(t K -t p ))] ) where n = +l,fti = -3, £2 2 = +3, fi 3 = -1 F = instantaneous fishing mortality rate (0.251) R = recruitment (1,000,000 fish/yr) M = instantaneous mortality coefficient (0.36) t P ' = age of recruitment (3.0 yr) t K = maximum age by which time all flounders die(18yr) K = growth coefficient. The yield-isopleth diagram (Fig. 19) represented the situation believed to be closest to that of St. Marys Bay fishery. The sustained annual yield of over 0.5 million pounds predicted by the model agrees with the observed total landings for the past 3 yr. The model showed that catches will increase only if flounders are captured at smaller sizes and fished harder than at present. There- fore, there was little basis for restrictive regulation of the fishery as this would tend to lower the annual yield. Total fishing effort in the bay was limited by returns per unit effort. Therefore, St. Marys Bay flounder fishery is probably realizing the maximum sustained yield pos- sible under present market conditions. Saila et al. (1965) utilized available data on winter flounder vital statistics to get a preliminary theoretical estimate of the size of a population of juvenile winter flounder necessary to sustain or increase the yield of a commercial fishery for the species in Rhode Island Sound. Equations used to estimate equilibrium yield are: Y = T=T F T P T(o ) (i + exp[g - ZT\ ) E T=T r 2 Y E = equilibrium yield T = successive intervals or periods in the life of the fish T r = tbe first period under consideration T — the last period under consideration F = instantaneous rate of fishing mortality Z = instantaneous rate of total mortality g = instantaneous rate of growth in weight. Coefficient values were derived from the data of Saila et al. (1965) and Pearcy (1962a). Fishing mortality was cal- culated on the basis of Rhode Island trawl landings for a 10-yr period. Figure 20 illustrates three surfaces repre- senting the stock weights (in grams) of winter flounder at 5 mo of age necessary to produce an equilibrium yield of approximately 2 million pounds. The lowest surface uses a conservative estimate of Z, the middle surface an average value, and the upper surface a slightly higher one. The stock weight of newly metamorphosed juveniles necessary to sustain the empirical average yield under average mortality coefficients for all life history stages was 6.5 X 10 6 g or 1.8 X 10'° individuals. The stock weight of juvenile flounder at an age of 5 mo was a signifi- cant proportion of the equilibrium yield. Growth ap- peared to be very rapid during the early life history stages and this provided for a significant early increase in biomass over and above the amount removed by natural mortality. The effect of natural mortality is more sig- nificant than the fishing mortality, and research on in- creasing the basic productivity of nursery areas would have a high probability of success in terms of improving the fishery. 4.6 The population in the community and the ecosystem Dexter (1944) classified the winter flounder as a domi- nant which exerts control over the Strongylocentrotus- Buccinum community by occupying and holding space. The community extends from spring low water to a depth of about 27 m and latitudinally from the northern part of Cape Cod to the boundary of the cold Labrador Cur- rent off the coast of Maine. It is characterized by echino- derms, large gastropods, skates, sculpins, flounders, and decapod crustaceans. 31 200.000 500.000 600.000 B .2 .4 .6 .8 10 12 14 1.6 18 £0 a. 3 \- Q. < U H 6.0 5.0 C 4.0 3.0 20 yrVgrgr nC P 1.050.000 1.100.000 1.160.000 J I I I I L J L. .2 .4 .6 .8 IP 12 1.4 1.6 18 20 -v MO.I5 K-0.40 J I 5.0 100 60 50 4.0 30 2P V* 500.000 60OO00 700000 750.000 D -L -L 75O0O0 J L I L .6 .8 IP 12 14 16 18 2p F- INSTANTANEOUS RATE OF FISHING +■ MOl25 K-CU5 5.0 J I IQO 2. A Figure 19.— Yield isopleth diagrams for the St. Marys Bay flounder fishery (from Dickie and McCracken 1955). 32 r5.0 x 10* •4.5 x lO 6 ^^ / ■4.0 xlO 6 / / 2 / =i / o / z ■3.5 xlO 6 / / "? / ti- ■ZQ\\0*^f / / / w / / <" / / < / / * ■2.5 xio 6 // J / / o 1 / m ■2.0 x10 s / / / / / 1 1 / 1.5 xlO 6 / / / ^ ► 1 . x V&s^'^ / L^y X44 ■0 5x10°/ / "X28 M ■" — 1 1 1 1 1 1 y<20 U2 60 .874 794 .714 .634 .554 474 .394 F Figure 20. — Stock weights of winter flounder at age 5 mo required to produce an equilibrium yield of approximately 2 million pounds for three values of Z for the first 5 mo. Lowest surface, Z = 1.655; middle surface, Z = 1.855; and upper surface, Z = 2.055. (From Saila et al. 1965.) Richards (1963) analyzed the demersal fish popula- tion of Long Island Sound from a sand-shell bottom and a mud bottom. The 10 most common species (of 37 species, 3,949 individuals) constituted 93% of the total standing crop. The winter flounder was the most abun- dant species composing 67% of the standing crop in both bottom types. There were two groups of species, residents and migrants. The chief residents besides winter floun- der were the windowpane, Scophthalmus aquosus, and the hake, Merluccius bilinearis. The chief migrant was the scup, Stenotomus chrysops. In general, fishes were more abundant in fall, decreased early in winter, in- creased in late winter, and reached a low in summer. The sand-shell station was characterized by a high percentage of sand and gravel. It was occupied by a bio- mass of epifauna five times that of infauna of which the epifauna dominates the diets of prey species. Winter flounder dependence on polychaetes separated it from most other predators, and its omnivorous tendencies precluded extensive competition. Immigration of migra- tory predators increased chances for interspecific com- petition, but this was kept to a minimum (except for S. aquosus) by the abundant and well distributed food resources and absence of territoriality among the predators. The community was heterogeneous. Juvenile production was 0.06 g/m 2 per year. Trophic level conver- sion figures based on consumption of epi- and infauna showed infauna productivity was sufficient to support the species without additional epifauna but efficiency of food conversion was low, and it did not appear to make maximum use of available food (Richards 1963). Tyler (1971) described periodic and resident com- ponents of a northern Atlantic fish community located in Passamaquoddy Bay, New Brunswick. Temperature ranges for this area were 1.2°-10.1°C, salinity 29.5- 22.3% o . The bottom was sloping, 38-55 m in depth, and covered with brown mud. Tyler concluded that in tem- perate regions, inshore deepwater fish communities are made up of three groups of species — one present during winter only, one during summer only, and a third throughout the year. The winter flounder was one of the most numerous members of the resident community. The population exhibited seasonal fluctuations in abun- dance related to spawning time, the maximum occurred in April and May. Tyler believed formation of temporal groups was mainly related to temperature regime, the greater the annual temperature fluctuation the more species in the temporal and the less in the regular com- ponent. Thus community stability was directly related to temperature stability. This was a food limited produc- tion system (Tyler 1972b) and there was, in general, over- lap in diets of the principal species of the community. The principal prey of the year-round residents were the same during the summer and winter except that four ad- ditional prey species were taken in summer. When win- ter seasonal species emigrated, the prey species were exploited by summer and year-round residents. When summer seasonals left, the principal species unique to them were unexploited. Derickson and Price (1973) studied the shore zone of Rehoboth and Indian River Bays, Delaware River. They collected 46 species and 41,286 individuals. The five most ecologically important species in order of abundance were Fundulus majalis, Menidia menidia, Fundulus heteroclitus, Pseudopleuronectes americanus, and Anchoa mitchilli. Combined average biomass estimates for the five SDecies were 5,500 kg/km 2 and 2,800 kg/km 2 for Rehoboth Bay in 1968 and 1969, respectively, and 7,600 kg/km 2 and 3,700 kg/km 2 for Indian River Bay in 1968 and 1969, respectively. Greatest species diversity and abundance occurred in summer, probably because the bays were used as a nursery and feeding grounds. The numbers of individuals and species showed a direct rela- tionship to seasonal temperature. Winter flounder abun- dance showed no relationship to substrate type, vege- tation, and water current velocity, but water depth and temperature were important to various life stages of flounder. 33 Oviatt and Nixon (1973) described the community structure in Narragansett Bay. The 10 most important species made up 91% of the catch (Table 21). Winter flounder was the most abundant species. There was no clear pattern of fish abundance except for higher diver- sity at the mouth of the bay. Bay characteristics were: relatively unpolluted, covers 259 km 2 , has a small salini- ty range (24-30%o), temperature range from -0.5° to 25°C, weak seasonal stratification, and depths up to 40 m. East Passage is deeper than West Passage. Both were dominated by fine sediments with sand present at the mouth of the Bay and upper West Passage. The only year-round residents of the Bay were winter flounder and sand dab (windowpane). Scup, butterfish, weakfish, and sea robin were summer species only; winter species were sea herring, blue back herring, torn cod, and sculpin. The total species diversity expressed as the Shannon Weiner Index was 3.22. The high was in October and the low in January which is opposite to tnat reported by McErlean et al. (1973) for Chesapeake Bay. Table 21. — Important fish species by number and percent of two eco- systems. Species rank for 101 trawls at regular stations throughout the year. Percent Total Common name Scientific name of total number N'arragansett Bay, R.I.' Winter flounder Pseudopleuronectes americanus 36 3,361 Windowpane Scophthalmus aquosus 14 1,287 Scup Stenotomus chrysops 10 915 Butterfish Peprilus triacanthus 9 871 Weakfish Cynoscion regalis 8 718 Northern sea robin Prionotus carolinus 6 f,i;.i Red hake Urophycis chuss 3 2? ■■ Barred sea robin Prionotus mart is 2 186 Cunner Tautogolabrus adspersus 2 179 Little skate Raja erinacea Mystic River estuary, Mass. 2 1 126 Winter flounder Pseudopleuronectes americanus 53 1,465 Rainbow smelt Osmerus mordax 32 890 Alewife Alosa pseudoharengus 7.6 186 Atlantic herring Clupea harengus 5.9 163 Atlantic menhaden Brevoortia tyrannus 0.9 27 Blueback herring Alosa aestiualis 0.7 19 Ocean pout Macrozoarces americanus >0.1 4 Grubby Myoxocephalus aenaeus >0.1 3 Cunner Tautogolabrus adspersus >0.1 3 Atlantic mackerel Scomber scombrus >0.1 3 Oviatt and Nixon (1973). Haedrich and Haedrich (1974). the system, they might be important in regulating diver- sity and abundance of other members of the benthos. Haedrich and Haedrich (1974) surveyed fishes in the Mystic River estuary, Mass. It is a mixed, almost homo- geneous estuary with a tide range of 2-4 m, salinity 29- 32% , and temperature 5°-18°C (bottom 3°-14°C). The lower 2 km of the estuary has been dredged. A power plant was located on the upper end of this stretch; heat- ing effects are minimal, but discharge may be 10° higher than the intake temperature. The midstream tempera- ture of water near the plant was rarely higher than 1° of that downstream. The estuary was highly polluted: DO 1-6.8 ppm but generally less than 50% saturated, pH 6.5- 8.0 with a high concentration of organic nutrient, and coliform counts in concentrations as high as 30,000 cells/100 ml. Oily residues and hydrogen sulfide were pres- ent in the sediments. A benthic community analysis showed very low diversity dominated by the polychaete, Capitella capitata, a pollution indicator organism. Total number of fishes caught was 2,778 of 23 species; total weight was 1,631 kg. The 10 most abundant species are given in Table 21. This assemblage was similar to other northern fish communities with periodic and resident species; the winter flounder was a resident, completing its entire life cycle in the estuary. Catch rates for the es- tuary were lowest in June by numbers and weight and in- creased, thereafter, throughout the year. The mean rate of biomass caught was 24 kg/h or 2 g fish/m 2 . Diversity in numbers was at its highest in June and lowest in August; species diversity was greatest in November (see Fig. 15). Biomass diversity indicates complexity of energetic relations in the food web; in this estuary, diversity was low and winter flounder were major channels of energy flow at the fish trophic level. The community had a dy- namic period from November to August and a static one from summer to early winter. Food competition between major species was not likely as the three major fish species have very different food habits. They do not com- pete for space and the breeding time is different for all three species. Pooled annual diversity, a measure of com- munity structure designated H, was 1.19 on numbers and 0.71 on weight. These values were low, but close to those obtained by McErlean et al. (1973) from the Patuxent River, Md.; suggesting this diversity level might be characteristic of temperate estuaries. 5 FISHING 5.1 Fishing equipment The winter flounder population was not aggregated (K = 1) and the maximum K value (a measure of ag- gregation) of 7.3 occurred in the fall. There was little dif- ference in seasonal means (spring 8,151/km 2 , summer 6,669/km 2 , fall 7,163/km\ and winter 11,856/km 2 ). Trophic relationships were such that the two major species, winter flounder and windowpane, did not com- pete for food. The mean annual biomass of demersal fishes was 31,876 kg/m'. Although the abundance of demersal fishes was small with respect to other parts of 5.11 Gears The most common gear used in the winter flounder fishery is the otter trawl (No. 35 Yankee). Dickie and McCracken (1955) gave the mesh size in the belly as 4 in (10.2 cm) between knot centers as purchased and in the cod end about 3 in (7.6 cm). Motte et al. 1973 12 described ,2 Motte, G. A., A. J. Hillier, and R. P. Beckwith. 1973. Bottom trawl performance study. Univ. R.I. Mar. Tech. Rep. Ser. No. 7. Un- paged. 34 the trawl in detail (Table 22). Although there is a pound net fishery in the Chesapeake area and a fyke net fishery in the Middle Atlantic region, these fisheries are declin- ing. Perlmutter (1947) gave a history of the development of the fishery in the New York area. Before 1895 fish were taken by fyke net and traps. As consumer demand in- creased, more efficient gear was used. In 1895 the beam Table 22.— Description of Yankee 35 Otter Trawl (Motte et al. 1973). Length X Line diameter Material Attachments Headline 52 ft Combination Floats: 8 or 19 X 8 Bosom 12 ft X 5/8 in in. diam. plastic Each wing 20 ft X 5/8 in Footrope 72 ft Chain Bobbin gear: 4-in Bosom 10 ft X 3/8 in diam. rubber discs, Each wing 31 ft X 3/7 in full length of footrope Hanging line 89 ft X 5/8 in Polypropylene- Dacron Wing lines 6 ft X 5/8 in Polypropylene- Dacron Wing bridles Upper 60 ft X 3/8 in Steel wire chain Lower 60 ft X 3/8 in Door legs Upper 7 ft X 5/16 in Chain Doors: standard Lower 7 ft X 5/16 in Chain rectangular 3 ft X 6 ft X 1 to in 236 lbs Towing warps 7/16 in Steel wire Motte, G. A., A. J. Hillier, and R. P. Beckwith. 1973. Bottom trawl performance study. Univ. R.I. Mar. Tech. Rep. Ser. No. 7. Unpaged. trawl was introduced in the flounder fishery of Massachusetts. By 1915, the Cape Cod fishery had changed to otter trawls and there was a shift from sail to gasoline and diesel engines which made it possible to fish a greater area. By 1920 the winter flounder fishery was at its peak, but during the 1930's fishermen reported decreasing catches on major grounds; therefore, a mar- ket developed for yellowtail flounder, Limanda ferruginea. During the 1960's the winter flounder fishery increased again. 5.12 Boats Dickie and McCracken (1955) described boats used in the Newfoundland winter flounder industry. Originally there were two types of boat: 1) large boats 40-45 ft long with gasoline engines, about 100 hp, which towed 50 ft "flounder drags" or No. 35 Yankee trawls; these boats began fishing earlier in spring, and 2) smaller Cape Is- land type open boats 30-40 ft long with gasoline marine engines and power-driven winches. By 1951 the large boats stopped fishing for winter flounder. Olsen and Stevenson 11 described commercial fishing boats used in Rhode Island waters. There were three "Olsen, S. B., and D. K. Stevenson. 1975. Commercial marine fish and fisheries of Rhode Island. Univ. R.I. Mar. Tech. Rep. 34, 117 p. groups of trawlers: 1) day boats 40-60 ft long fishing the nearshore grounds with a three-man crew, which leave and return to port the same day, 2) short-trip boats, es- sentially the same as day boats but making trips of 1-3 days, and 3) long-trip boats 55-85 ft long fishing the off- shore grounds such as Nantucket shoals and Georges Bank, carrying a three- to six-man crew and making 3- to 6-day trips. These boats had larger engines and were usually equipped with radar. 5.2 Fishing areas 5.21 General geographic distribution The general geographic distribution is the northwest Atlantic (FAO Statistical Area 21) on the coast of North America from Labrador to Cape Hatteras, N.C. (Fig. 2). 5.22 Geographic range Winter flounder are found within 15 mi (24.2 km) of the shore and on offshore banks. They enter estuaries and may be found in brackish waters of many rivers. They are most abundant from Nova Scotia to New Jer- sey in inshore waters (Perlmutter 1947). There are also large populations on Georges Bank and Nantucket Shoals. 5.23 Depth range Tide mark to 20 fathoms (40 m), they extend to 50 fathoms on the offshore banks. The depth record is 70 fathoms (Bigelow and Schroeder 1953). Variations of density with depth have been discussed in sections 4.12 and 4.24. 5.24 Conditions of the grounds Olsen and Stevenson (see footnote 13) stated that in Rhode Island waters, winter flounder can be caught over all types of bottom, but in salt ponds and estuaries they preferred muddy sand. Bigelow and Schroeder (1953) reported that on offshore banks they were common on hard bottom. 5.3 Fishing seasons 5.31 General pattern of seasons Early spring to late fall. 5.32 Dates of beginning, peak, and end of season See Table 23. 5.33 Variation in date or duration of season The season generally begins after adults have spawned and begun to move into deeper water. Factors affecting this are covered in sections 3.16 and 3.51. 35 Table 23.— Fishing seasons for winter flounder. Area Season Peak Minimum Author Long Island Feb. -June Apr. -May Lobell(1939) Rhode Island Year-round May -July Winter Olsen and Stevenson (1975)' Si MarysBay, Mar -Winter Apr. -July Winter Dickie and Nova Scotia McCracken (1955) Lone Island Mar. -Nov. Apr. -May Winter Briggs(1965) sports fishery Olsen. S. B.. and D. K. Stevenson. 1975. Commercial marine fish and fisheries of Rhode Island. Univ. R.I. Mar. Tech. Rep. 34, 117 p. 5.4 Fishing operations and results 5.41 Effort and intensity Dickie and McCracken (1955) calculated fishing effort in the St. Marys Bay, Nova Scotia, fishery by compiling average catch per 50-ft net per hour from boats which fished exclusively for flounder. To compare the drop in catch per effort with the history of the fishing intensity they divided the total landings of flounders from the catch by the catch per unit of effort by 50-ft nets. Edwards (1968) computed exploitation rate by cal- culating the average catch in pounds per tow for ICNAF Subarea 5 (New England) made by the 1963-66 ground- fish survey using a 36 Yankee Trawl with a 0.5-in (1.3- cm) cod end liner. The trawl had a bottom spread 35-40 ft (10.7-12.2 m) and a maximum height of 7ft (2.1 m) at the middle. Biomass was calculated by applying a cor- rection factor of the number of square miles for the zone divided by area the net sweeps each tow (0.016 mi 2 ) to the catch per tow in pounds. Results of both calculations are presented in Table 24. Briggs (1965) calculated catch per unit effort of winter flounder by sportsmen fishing from five different facili- ties (bank and pier, rowboat, open boat, charter boat, and private boat) in four different locations around Long Island (Great South Bay, Shinnecock Bay, Gardiners Bay, and Moriches Bay) for each month in 1961-63. Open Table 24.— Fishing effort for winter flounder in St. Marys Bay and ICNAF subarea 5. Landings by Landings Propor- Total 50-ft nets' by all nets' tion taken by effort by Catch/h 50-ft Year Total in lbs (lbs) 50-ft net' net 1 1953 253,111 110 421,071 0.60 3,828 1952 152,047 105 369,262 0.41 3,517 1951 99,636 152 586,111 0.17 3,856 1950 487,656 188 1,299,176 0.38 6,911 1949 354,024 4 1 5 737,403 0.48 1,777 1948 272,018 476 294,000 0.93 626 Catch per unit tow in pour ids 2 Southern Browns New E ngland Georges Bank Offshore Shoal Offshore Gulf of Maine Bank Inshore Shallow Middle Deep 8.01 4.99 0.01 11.44 0.55 0.09 0.13 boat and charter boat anglers had the best catch per unit effort in the bays. Catch was highest in spring and lowest in summer (16-20 fish per angler per trip in spring, 10 or less in summer). Bank and pier anglers had the lowest catch per unit of effort. 5.42 Selectivity Dickie and McCracken (1955) stated that nets with a mesh size of 4 in (102 mm) between knot centers in the belly and 3 in (76 mm) in the cod end take flounder down to 200 mm in size, but in the Nova Scotia fishery, fish plants place a minimum of 300 mm on flounder size. 5.43 Catches Total annual yields in Table 25 include the world yield and the U.S. yield by states. For maximum equilibrium yield see section 4.5. Table 26 is the sports fishery yield of the United States by geographic section. 6 PROTECTION AND MANAGEMENT 6.1 Regulatory (legislative) measures Poole (1969) reported the State of New York Fish and Game Law prohibits buying, selling, or offering for sale, winter flounder less than 8 in (206 mm) long. Howe and Coates (1975) reported Massachusetts prohibits otter trawling at all times north of Boston and in Buzzards Bay. In most other areas trawling is prohibited from 1 April or 1 May to 31 October. Trawl regulations by the International Commission for the Northwest Atlantic Fisheries in relation to bottom fisheries, prohibit use of trawl nets with cod end meshes of dimensions less than 130 mm in manila twine netting or the equivalent when materials other than this are used to take winter flounder in subarea 4 (Bogdanov and Kon- stantinov 1973). See Figure 2. 6.3 Control or alteration of chemical features of the environment Eisler (1965b) studied acute toxicity of alkyl benzene sulfonate (ABS), a surfactant present in detergent, to five estuarine fish species. The fishes, Menidia menidia, Fundulus heteroclitus, Mugil cephalus, Anguilla ros- trata, and Pseudopleuronectes americanus, were col- lected from New Jersey. Tide detergent, used as a source of ABS, contained 30.3% ABS. The winter flounder was intermediate in susceptibility; 8.2 ppm detergent was the L.C 50 after 96 h exposure at 20% o salinity and 20° C. After 12 wk in solution, the detergent retained its toxici- ty. Sprague and Carson 14 did preliminary screening tests Dickie and McCracken (1955). 'Edwards 0968). "Sprague, J. B., and W. B. Carson. 1970. Toxicity tests with oil dis- persants in connection with oil spills at Chadabucto Bay, Nova Scotia. Fish. Res. Board Can., Tech. Rep. 201, 30 p. 36 Table 25. — Annual yield of winter flounder in world and U.S. commercial fish- eries.' 1965 1966 1967 1968 1969 1970 1971 1972 1973 1,000 t — - Canada 5.2 3.3 2.7 1.2 2.5 — — — — U.S. 11.6 14.7 12.3 9r> 11.3 12.1 11.6 7.2 9.7 Total 16.8 18.0 15.0 10.7 13.8 12.1 11.6 7.2 9.7 New Massa- Con- New Hamp chu- Rhode necti- New Jer- Dela- Mary- Vir- Year Maine shire setts Island cut York sey ware land ginia 1.00C 1973 L86 8 10.914 4,414 844 1,661 160 2 2,200 900 1972 280 10 11,344 4,634 38 1,429 94 2 3 21 1971 146 7 14,542 5,275 817 1,660 79 5 17 55 1970 298 8 15,898 5,301 789 1,692 146 3 •21 123 1969 96 4 15,616 4,300 931 1,444 268 2 60 394 1968 45 — 11,996 3,362 1,041 1,826 4 2 2 3 7-4 824 1967 103 — 16,419 3,844 886 2,931 366 19 178 798 1966 92 — 21,085 4,275 831 3,259 438 50 91 220 1965 69 — 16,520 3,638 727 2,245 279 38 62 122 1964 75 — 13,901 4,080 957 1,441 357 4H 26 68 1963 45 — 11,786 2,918 983 1,834 185 37 10 2 1962 1961 158 — 11,934 2,028 980 1,695 152 20 3 1 'From Fishery statistics of the United States. National Marine Fisheries Service, Statistical Digest numbers 54-56 for the years 1961-73. Table 26.- -Sports fishery statistics for winter flounder in 1970 and 1965 by survey re- gion (from Deuel 1973 and Deuel and Clark 1968). Year Region I North Atlantic New Engl and-New Jersey No. No. Wt. offish anglers fish (1,000 lbs) Region II Middle Atlantic New Jersey-Cape Hatteras No. No. Wt. offish anglers fish (1,000 lbs) Total 1970 563 42,949 24,684 402 18,632 12,801 1965 579 40,014 21,838 277 7,256 6,935 Number of fishes of all species caught by U.S. salt water anglers in 1970 21,581 7,496 29,077 of oil dispersants, manufactured for use in cleaning up oil spills, for acute toxicity to aquatic life. The test procedure used a static system with a given concen- tration of test mixture. Exposure continued for 7 days, after which several fish were removed and held in clean running water for 7 more days to check for delayed mor- tality. Test results gave an indication of acute lethal ef- fect only. There may be long-term or sublethal effects at concentrations of oil dispersants lower than those dis- cussed (Table 27). A classification scheme for "grade of toxicity" adapted from a report by the Joint Group of Experts on the Scientific Aspects of Marine Pollution (1969) was employed to describe toxicity (Table 27). Bunker C oil was "practically nontoxic" by 4-day criteria, but in 7-day tests, including 7-day postexperi- ment mortality, it was "slightly toxic" to winter floun- der (5°C 1,000-3,000 mg/liter). Corexit 8666 was "prac- tically nontoxic" as was its dispersion with Bunker C oil. An apparent toxicity during degradation should be in- vestigated before Corexit 8666 is considered for wide- scale use. Fish which died in Corexit alone had gill rakers and throats covered with white particles, apparently Corexit in mucus. This suggested Corexit caused mucus secretion around the affected areas and could be a factor Table 27. — Four-day median lethal concentrations of various oil dispersants, alone or mixed with Bunker C oil, to winter flounders and grading system used to describe toxicity at 5°C (from Sprague and Carson 1970).' Bunker C oil Corexit 8666 Corexit 8666 and oil BP1100 + oil Disperaol SD Grade "Practically nontoxic" Grade 1 "Slightly toxic" Grade 2 "Moderately toxic" Grade 3 "Toxic" Grade 4 "Very toxic" > 10,000 mg/1 > 10,000 mg/1 > 10,000 mg/1 32 mg/1 > 1,000 mg/1 Acute toxicity threshold above 10,000 mg/1 Threshold 1,000-10,000 mg/1 Threshold 100-1,000 mg/1 Threshold 1-100 mg/1 Threshold below 1 mg/1 'Sprague, J. B., and W. B. Carson. 1970. Toxicity tests with oil dispersants in connection with oil spills at Chadabucto Bay, Nova Scotia. Fish. Res. Board Can. Tech. Rep. 201, 30 p. 37 in mortality, hut this could also have happened after the t'ish began dying. Smith and Cole (1970) examined the effects of chlorinated hydrocarbons DDT. heptachlor, dieldrin in- secticide residues, and two related breakdown products DDE and heptachlor epoxide, on winter flounder juveniles and adults from the Weweantic River estuary, Mass. Topp (1968) compared larval mortality of winter flounder in the Weweantic to that data compiled by Pearcy (1962a) for the Mystic River estuary, Conn., and found excessive mortality in the former. He felt this might be due to pesticide contamination which drained from cranberry bogs along the Weweantic River water- shed and from county mosquito control programs. Winter flounder contained residues of the above com- pounds in their tissues. In nonmigratory juveniles, seasonal patterns were demonstrated for DDT, hep- tachlor. DDE, and heptachlor epoxide. Peak concen- trations of parent compounds were more closely associated with high runoff conditions than with specific applications of pesticides in the drainage system. Dieldrin was present uniformly throughout the year. Migratory adult flounder present from October to May contained heptachlor and heptachlor oxide levels similar to juveniles but significantly less DDE (Table 28). Com- parisons of chromatographic patterns of these flounders with flounders from widely separated coastal popu- lations and offshore Georges Bank flounders showed that the Wew-eantic population had a unique pattern quite dissimilar from other populations inferring that local pesticide levels can establish area specific chroma- tographic patterns. Adult female flounder sequentially concentrated DDT, DDE, and heptachlor epoxide in their ripening ovaries as spawning season approached (Table 28). Ovarian concentrations of insecticide residue may have caused the high larval mortality at final yolk sac absorption reported by Topp (1968), because residues were bound to yolk fats where they remained inactive un- til those fats were metabolized by the developing egg. At this time DDT would be released and would cause death. Eisler (1970) reported juvenile winter flounder were in- termediate in susceptibility to endrin, p,p'-DDT, and heptachlor on the basis of LC 50 (96 h) tests conducted with 10 species of marine fishes. Janicki and Kinter (1971) reported inhibition of ATP - ase activity by DDT and its commercial solvents cyclo- hexanone and DMF (N,N dimethylformamide) in win- ter flounder from the Gulf of Maine. They found measurable inhibition of Na + , K + , Mg + + , ATP-ase ac- tivity in the intestinal mucosa at 1 ppm concentration DDT which was linear through 50 ppm. The gills tested with DMF and 50% ppm DDT showed ATP-ase activity 54% inhibited. Cyclohexane completely inhibited ac- tivity. This inhibition of ATP-ase activity hindered ac- tive secretion of salt through gills which is important in maintaining tissue osmolarity. These observations may explain the sensitivity of teleosts to DDT. Baker (1969) experimented on histological and ultra- structural effects of high (3,200 and 1,000 fig/liter), medium (560^g/liter), and low (180A