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Shrimp Culture Research at
Texas AfdM University:
1989 to 1991

i Texas Agricultural Experiment Station ' Eclwarcl A. Hiler, Director ° The Texas AfiM University System ° College station, Texas

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Shrimp Culture Research at Texas A&M University:
1989 to 1991

A. Lawrence, F. Castille, T. Samocha, W. Bray, and L. Robertson

Texas Agricultural Experiment Station
Texas A&M University System
P.O. Box Q
Port Aransas, Texas 78373

P. Frelier

Department of Veterinary Pathobiology
Texas A&M University
' College Station, Texas. 78843

Abstract

The following accomplishments in shrimp mari-
culture research were completed in 1989, 1990, and
1991. Growth trials conducted on Penaeus vannamei
in outdoor tanks indicated that (1) a substrate was
not necessary for optimal growth; (2) requirements
for some minerals could be satisfied from the sub-
strate and seawater, the substrate being more im-
portant than seawater; and (3) production was greater
at low than at high salinities. However, the growth
at high salinities could be increased by raising the
protein level of the feed.

Growth studies of Penaeus vannamei in pens in
earthen ponds demonstrated that (1) growth (2.31 to
2.22 g/week) and production (6,608 to 6,636 kg/ha)
were similar for feed rates of 4 to 8 percent body
weight per day but greater than a feed rate of 2 per-

cent body weight per day (1.70 g/week and 5,912 kg/D

ha); (2) growth was either equal to or greater in
shrimp fed during the day than in shrimp fed at night;
(3) growth increased as feeding frequency increased
from 1 to 4 times per day, (4) shrimp fed a 25 percent
protein feed had a similar growth and harvest biom-
ass (2.09 g/week and 6,723 kg/ha) to those fed a 45
percent protein feed (2.31 g/week and 6,606 kg/ha);
(5) shrimp fed a commercial feed containing 35 per-
cent protein and 2.5 percent squid meal had similar
growth and production rates (2.29 g/week and 6,989
kg/ha) to those presented a feed containing 45 per-
cent protein and 15 percent squid meal (2.30 g/week
and 6,578 kg/ha); and (6) growth and production were
2.19 g/week and 6,232 kg/ha using 13 mg vitamin C
per kg of feed and 2.22 g/week and 6,288 kg/ha using
246 mg vitamin C per kg of feed. Growth trials con-
ducted on native species in pens in earthen ponds

Keywords: shrimp, pond and raceway production,
nutrition, disease.

UBRAQV
AUG 1  ‘i994

demonstrated that a harves-Eabhhssof
and 2,443 to 2,578 kg/m’ and a growth rate of 0.93 to
1.04 and 0.69 to 0.76 g/week was obtained with P.
setiferus and P. aztecus in pens in earthen ponds and
that similar growth and survival were obtained for P.
setiferus and P. vannamei fed 28 percent protein feeds.
With P. vannamei, growth of more than 2 g/week was
obtained for at least one treatment in six different
experiments conducted in either outdoor tanks or pens
within earthen ponds.

Intensive round pond technology was transferred
from Oceanic Institute in Waimanolo, Hawaii, to
Texas. Its use demonstrated that intensive produc-
tion (growth rates of 1.82 to 1.90 g/week and harvest
levels from 7,229 to 9,107 kg/ha) of Penaeus vannamei
in square ponds was similar to that in round ponds
having a bottom area of about 0.07 to 0.1 ha.

New technology was developed for removing
waste and for water aeration and circulation for nurs-
ery raceway production of Penaeus vannamei. More
than 7,000 juvenile Penaeus vannamei per m’ with a
minimum of 92 percent survival and a food conver-
sion ratio (FCR) of about 0.6 in raceways were suc-
cessfully produced using this system. In addition,
raceway technology was developed for production of
6.5 to 8.1 g P. vannamei with survival and produc-
tion of 78 to 83 percent and 13,600 to 15,600 kg/ha,
respectively, at an initial stocking density of 233 or
299 PL/m’.

A method for evaluating Penaeus vannamei
postlarvae (PL) quality was developed. It indicated
that lower quality postlarvae have a lower growth
rate in the nursery phase.

Research on shrimp diseases indicated that
Necrotizing Hepatopancreatitis (NHP) and the Texas
Pond Mortality Syndrome (TPMS), synonym
Granulomatous Hepatopancreatitis (GH), does not
appear to be correlated to the presence of IHHNV
inclusion bodies, and hence IHHNV is not a factor in

this disease. Use of oxytetracycline (OTC)-medicated
feed markedly increased the harvest biomass in 1990
(6,569 kg/ha) versus that of 1989 (881 kg/ha) and 1988
(1,025 kg/ha) on a commercial shrimp farm in Texas.
Husbandry practices oriented toward production of
specific pathogen-free (SPF) postlarvae for grow-out
to marketable size were developed to maintain SPF
broodstock.

Although a tremendous amount of new technol-
ogy has been developed during the last 3 years, com-
mercial shrimp culture in Texas is still marginal.
Additional technology is needed in terms of intensifi-
cation of raceway and pond culture, feeds and feed-
ing strategies, disease prevention, and development
of high-quality shrimp populations.

Introduction

The shrimp culture research effort during the last
3 years has been in four areas: ( 1) intensification of
raceway and pond culture; (2) feeds and feeding strat-
egies; (3) disease prevention; and (4) development of
high-quality shrimp populations. In this review, an
attempt will be made to give an overview of the re-
search conducted at the Shrimp Mariculture Project,
Texas Agricultural Experiment Station, Texas A&M
University System.

Intensification of Raceway and
Pond Culture

Demonstrated that Penaeus vannamei pro-
duction in tanks without substrate and in lined
ponds is equal to or better than production in
tanks containing either sand or clay substrate
and unlined ponds.

Conceptually, as shrimp culture in earthen ponds
intensifies, maintaining desired quality of the pond
bottom substrate will become increasingly difficult.
Three experiments were conducted in outdoor tanks
using different culture conditions in the presence of
substrate (either sand and clay) and in the absence
of substrate (bare bottoms). In the first experiment
using either seawater from a power plant cooling lake
or from a natural bay (i.e., Laguna Madre), Penaeus
vannamei cultured at 45 ppt without substrate had
greater growth than in the presence of a sand sub-
strate. At 25 ppt, P. vannamei growth was the same
in the presence and absence of a substrate. In the
second experiment, using natural seawater at 27 and
45 ppt, growth of P. vannamei without substrate was
greater than growth with either sand or clay sub-
strates (Bray et al. 1990). The third experiment
showed there were no significant differences in growth
of P. vannamei either in the presence or absence of

substrate using either 10 ppt or 35 ppt seawater
(Davis et al. 1990). Thus, in all experiments, growth
of juvenile P. vannamei in outdoor tanks without sub-
strate was either greater than or the same as growth
in the presence of either sand or clay substrates.

'l\1vo trials were conducted by stocking Penaeus
vannamei into a single lined round pond and a single
round earthen pond (unlined) of approximately 0.08-
to 0.1-ha size (Bray et al. 1992). Table 1 gives data
from these two trials. In both trials, production of
harvest biomass from lined ponds was greater than
from unlined ponds in each trial. Growth rate, sur-
vival, and harvest size values were similar for the
shrimp cultured in lined versus unlined ponds.

Table 1. Data on Penaeus vannamei cultured in lined and un-
lined, small round ponds. Each value represents a single obser-
vatlon.

Parameter Trial 1 Trial 2

Lined Unlined Lined Unlined

pond pond pond pond
Stocking weight 1.33 1.31 1.32 1.32
(g/shrimp)
Stocking density 81.9 77.1 71.4 72.7
(shrimp m2)
Trial duration 70 70 92 92
(days)
Growth rate 1.82 1.86 1.25 1.23
(ti/week)
Survival 57.1 55.6 67.2 56.6
(°/<>)
Harvest size 19.5 19.9 18.1 17.4
(ti/Shrimp)

Harvest biomass 9,107 8,530 8,688 7,151
(ks/ha)

These data from experiments conducted in out-
door tanks and from production trials in small round
ponds suggest that production of Penaeus vannamei
in lined ponds would be either equal to or greater
than production in unlined ponds. Other advantages
of lined ponds include shorter time between crops,
reduced probability for development of substrate tox-
icity, and significantly greater ability to disinfect the
pond. Whether it is economically advantageous to use
lined ponds cannot be determined from available data
at this time.

Demonstrated that Penaeus vannamei pro-
duction in outdoor tanks increases as salinity
decreases from 49 ppt to 5 ppt.

Most people assume that high salinities decrease
growth of Penaeus vannamei. Thirty 1.2-m diameter
outdoor tanks with no substrate were stocked with
15 1.6-g juvenile P. vannamei per m2 bottom area for
37 days. Five salinities (with six replicates each) of
5, 15, 25, 35, and 49 ppt were evaluated. Survival

Table 2. Data on Penaeus vannamei cultured in either outdoor tanks or pens in earthen ponds. Each value represents the mean of 6
and 12 observations if the experiment is conducted in outdoor tanks or in pens in ponds, respectively. Experiment number ls in

parenthesis.

Outdoor tanks

(1) (2)
Stocking density 30 30
(shrimp/m?)

Salinity 12 46
(pm)

Feed quality 35 45
(% protein)

Trial duration 42 42
(days)

Growth rate 2.54 2.20
(g/week)

Survival 89.6 91.6
(%)

Harvest size 20.5 18.5
(g/shrimp)

Harvest biomass 5,512 5,082
(Kg/ha)

Parameter

rates did not differ significantly, but the final weight
of shrimp grown in 5 or 15 ppt seawater (12.2 and
11.9 g, respectively) were greater than those grown
in 25 and 35 ppt seawater (11.0 and 10.9 g, respec-
tively). Final weights of shrimp in 25 and 35 ppt sea-
water were greater than the final weight of shrimp
in 49 ppt (10 g) seawater (Bray et al. 1990). These
data definitely indicate that the growth of R vannamei
is greater at lower salinities of 5 to 15 ppt than at
higher salinities above 35 ppt.

Obtained growth better than 2 g/week of
Penaeus vannamei for at least one treatment
in six experiments conducted in either outdoor
tanks or pens in earthen ponds.

At initial stocking densities under various condi-
tions (e.g., salinities, feed quality, stocking densities,
etc.), growth rates from 2.17 to 2.54 g/week with ex-
trapolated harvest biomass of 5,512 to 7,180 kg/ha
were obtained for at least one treatment in each of
six experiments in outdoor tanks and pens in earthen
ponds (Table 2) (Robertson et al., 1992a, b, c, d). The
significance of these data is that the potential exists
for achieving Penaeus vannamei growth of more than
2 g/week in production ponds that yield more than
5,000 kg/ha and harvest sizes greater than 18 g. Thus,
a long-term goal would be to develop production tech-
nology with the necessary supporting physical sys-
tem (raceways and/or ponds) to achieve this poten-
tial high growth rate with larger production levels.
With growth rates above 2 g/week and “head start-
ing” the nursery phase in raceways under green-
houses, two crops per year of P. vannamei in south
Texas would be more economically feasible.

Transferred intensive round pond technol-
ogy developed at Oceanic Institute to Texas and

Pens in ponds

(1) (2) (3) (4)
4o 4o 4o 4o

33 33 33 33
25/45 45 35 45
42 42 42 42
2.32 2.17 2.22 2.45
88.4 90.9 82.3 83.9
19.7 18.8 19.1 20.5

6,983 7,180 6,288 6,876

demonstrated that intensive production
(growth rate of 1.29 to 1.32 g/week and harvest
levels from 7,151 to 8,530 kg/ha) of Penaeus
vannamei in square ponds was similar to round
ponds having a bottom area of about 0.07 to
0.1 ha.

Intensive round pond trials were initiated in 1989
and 1990 to transfer technology developed at the Oce-
anic Institute for production of shrimp in small round
ponds. Initial results obtained at the Oceanic Insti-
tute showed extremely promising results: 7,400 to
16,000 kg/ha/crop in 1988 and 1989. The production
achieved in the Texas trials varied from 7 ,151 to 8,530
kg/ha/crop (Table 3), corresponding to results at Oce-
anic Institute in 3 trials in 1989 to 1990 that pro-
duced 7,700 to 11,100 kg/ha/crop (Bray et al. 1992).

Table 3. Data on Penaeus vannamei cultured in square and round
small ponds. Each value represents a single observation.

Parameter Trial 1 Trial 2 -

Square Round Square Round

pond pond pond pond

Stocking weight 1.29 1.31 1.32 1.32
(st/Shrimp)
Stocking density 82.0 77.1 75.0 72.7
(shrimp/mg)
Trial duration - 70 70 92 92
(days)
Growth rate 1.90 1.86 1.01 , 1.23
(g/week)
Survival 43.4 55.6 67.7 56.6
(%)
Harvest size 20.3 19.9 14.6 17.4
(g/shrimp)

Harvest biomass 7,229 8,530 7,446 7,151
(ks/ha)

Particularly noteworthy is the lack of difference
in harvest biomass of Penaeus vannamei in square
versus round earthen ponds using the intensive round
pond technology. The growth rate, survival rate, and
harvest size are similar for P. vannamei cultured in
square compared with round ponds. Because the capi-
tal cost for construction of square ponds is less than
that for round ponds, this observation indicates that
small square ponds would be economically justified
compared with that of small round ponds.

Developed new technology for removing
waste and improving aeration and water cir-
culation for nursery raceway production of
Penaeus vannamei.

A new method of water circulation and waste re-
moval for raceway systems resulted in the produc-
tion of 14,200 and 18,900 kg/ha of juvenile Penaeus
vannamei (final weight was 0.48 and 0.77 g, respec-
tively) and a survival rate above 90 percent (Samocha
et al. 1993). Requiring less labor than others, the new
system provided better water circulation and more
efficient removal of the waste produced by shrimp. A
second trial of this new system successfully produced
more than 3,500 and 7,000 juvenile P. vannamei per
m” in 33 days with a minimum of 92 percent survival
at initial stocking densities of 4,000 and 7 ,800/m2,
respectively (Table 4). The small harvest size was due
to low mean seawater morning and evening tempera-
tures of 22.9 and 24.0 °C. Survival and harvest size
did not differ among the different stocking densities.
Notably, these shrimp had normal growth in commer-
cial production ponds even though low seawater tem-
perature caused slow growth in the 33-day nursery
raceway period.

Developed technology for production of 6.5
to 8.1 g Penaeus vannamei with survival of 78
to 83 percent and production of 13,600 to 15,600
kg/ha at an initial stocking density of 223 to 299
PL/m’ in raceways.

A 49-day intensive growth trial in 68.4-m2 race-
ways under greenhouse conditions was conducted
with 80-mg Penaeus vannamei at a density of 223 to
229 PL/m’. Shrimp grew at an average rate of 0.94 to
1.19 g/week. They were harvested at a mean size of
6.5 and 8.1 g. The harvest biomass reached 12,600
and 15,600 kg/ha, and 78 to 83 percent survived. Al-
though this trial was done during the spring in Texas
when ambient morning seawater temperatures
ranged from 18.3 to 283°C, temperatures in the race-
ways were maintained at a mean daily low tempera-
ture of 26.8 °C and a mean daily high of 29.8 °C
(Robertson et al. 1992c).

Feed and Feeding Strategies

Demonstrated that the growth of Penaeus
vannamei at high salinities of 46 ppt can be im-
proved by increasing the protein level of the
feed.

An experiment was conducted in outdoor tanks
with Penaeus vannamei (average stocking weight of
5.3 g and density of 30 shrimp/m’) using three feeds
(25, 35, and 45 percent protein levels) at two salini-
ties (12 ppt and 46 ppt) for 6 weeks (Robertson et al.
1992a). Salinity and protein level of the feed inter-
acted significantly. At 46 ppt, shrimp fed 45 percent
protein grew faster and had a higher harvest bio-
mass (2.2 g/week and 5,073 kg/ha) than did shrimp
fed 35 and 25 percent protein (2.02 and 1.89 g/week
and 4,463 and 4,073 kg/ha, respectively). At 12 ppt,
there was no significant difference in growth and
harvest biomass of shrimp fed either 35 or 45 per-
cent protein feeds. However, the shrimp fed 35 per-
cent protein feed had a higher growth rate and har-
vest biomass (2.54 g/week and 5,513 kg/ha) than did
shrimp fed 25 percent protein feed (2.3 g/week and
4,888 kg/ha). Results indicate that nutritional re-
quirements vary with culture salinity and suggest

Table 4. Data on 5- to 9-day-old postlarvae Penaeus vannamei (mean initial weight ls 2.16 mg/postlarva) cultured for 33 days in

raceways. Each value represents a single observation.

Parameter Raceway
1 2 3 4 5 6

Stocking density 7,830 4,040 7,830 4,290 7,830 4,290
(shrimp/mz)

Survival 92.5 108.5 96.9 107.8 95.2 99.0
(%)

Harvest size 0.070 0.064 0.060 0.062 0.064 0.080
(ta/shrimp)

Harvest density 7,240 4,380 7,580 4,630 7,830 4,290
(shrimp/m?)

Harvest biomass 5,080 2,810 4,610 2,900 4,770 3,420
(kg/ha)

FCR 0.66 0.57 0.72 0.64 0.65 0.66

(feed conversion ratio)

that use of higher protein feeds under hypersaline
culture conditions may produce higher yields.

Collected data indicating that Penaeus
vannamei obtain some of their requirements for
minerals from the substrate and seawater, the
substrate being more important than seawater.

An 8-week experiment was conducted with juve-
nile Penaeus vannamei using 42 1.2-m2 outdoor tanks
(Davis et al. 1990). Seven treatments with replicates
of six each evaluated growth and survival of shrimp
fed semipurified diets with and without mineral
supplementation at two salinities and in the pres-
ence and absence of substrate. The deletion of dietary
mineral supplementation at 10 and 35 ppt in the ab-
sence of substrate resulted in significant depression
of growth with no effect on survival. The depression
of growth was the highest at 10 ppt, indicating that
some minerals were obtained from seawater and/or
its associated biota. The data suggest (1) that the
greater the stocking density, the greater the neces-
sary mineral supplementation and (2) that culture
in lined ponds may require a higher mineral supple-
mentation in the diet than in unlined earthen ponds.

Demonstrated that the growth (2.31 to 2.22
g/week) and harvest biomass (6,608 to 6,636 kg/
ha) was similar for constant feed rates of 4, 6,
and 8 percent/day but greater than a constant
feed rate of 2 percent/day (1.70 g/week and 5,912
kg/ha) for Penaeus vannamei in earthen ponds.

Penaeus vannamei (6.67 g mean weight) were
stocked at a density of 40 shrimp/m2 into l-m’ pens
in an earthen pond for 42 days. The shrimp were fed
a 45 percent protein feed at 2, 4, 6, and 8 percent of
body weight, four times per 24-hour period. The data
in terms of growth rate, harvest size, and harvest bio-
mass indicate that a feed rate of 4 percent/day is ad-
equate for the conditions of this experiment (Table
5). It should be emphasized that if the growth rate
had been 1.0 g/week instead of the 1.7 to 2.3 g/week,
the required feed rate would probably be less than 4
percent.

Obtained data suggesting that Penaeus
vannamei fed during the day grew faster than
those fed at night and that growth increased as
feeding frequency increased from one to four
times per day.

Penaeus vannamei were stocked at a density of
40 shrimp/m’ into l-mz pens in an earthen pond and
fed 40 percent protein commercial feed one, two, or
four times during either the night or day (Robertson
et al. 1991b). The mean minimum and maximum tem-
peratures were 22.2 and 26.7 °C, respectively, with a
minimum oxygen tension of 5.3 mg/L. Growth in-
creased as the feeding frequency increased from one

Table 5. Data on Penaeus vannamei fed at various percentages
ot body weight per day. Each value represents a mean of 12
observations.

Parameter Feed rate
2% 4% 6% 8%

Growth rate 1.70 2.31 2.22 2.17
(g/week)

Survival 92.2 88.4 86.6 90.9
(%)

Harvest size 16.0b* 19.8a 19.2a 18.8a
(g/shrimp)

Harvest biomass 5,912 6,983 6,636 7,180

(kg/ha)

‘SNK (Student Newman Keul) groupings are indicated with lower-
case letters.

to four times per day. Growth of shrimp fed during
the day was marginally significantly greater (P =
0.0633) than growth of shrimp fed during the night.
Results indicate that feeding P. vannamei during the
day is at least as good as and may be preferable to
feeding at night.

Demonstrated that Penaeus vannamei fed
a 25 percent protein feed had a similar growth
and harvest biomass (2.09 g/week and 6,723 kg/
ha) to those fed a 45 percent protein feed (2.31
g/week and 6,606 kg/ha) in pens in an earthen
pond.

'I\ivo experiments stocked Penaeus vannamei at
densities of 30 and 40 shrimp/m’ into pens in an
earthen pond and fed them either 25, 35, or 45 per-
cent protein feeds at a 4 percent feed rate. One
additional treatment consisted of shrimp fed 25
percent protein feed for 14 days, 35 percent pro-
tein feed for the next 14 days, and 45 percent pro-
tein for the last 14 days. Surprisingly, none of the
treatments in both experiments differed signifi-
cantly. Growth rates were 2.09 to 2.32 and 1.85 to
1.97 g/week, and harvest biomass levels were 6,677
to 7,180 kg/ha and 5,101 to 5,255 kg/ha in shrimp
stocked at 40 and 30 shrimp/mz, respectively. These
data indicate that a much lower feed quality can
be considered for shrimp production levels rang-
ing from 5,000 to 6,000 kg/ha.

Demonstrated thatPenaeus vannamei fed
a commercial feed containing 35 percent pro-
tein and 2.5 percent squid meal had a similar
growth and production rates (2.29 g/week and
6,989 kg/ha) to those presented a feed contain-
ing 45 percent protein and 15 percent squid
meal (2.30 g/week and 6,578 kg/ha) in pens in
earthen ponds.

An experiment was conducted by stocking
Penaeus vannamei at 40 shrimp/mz into pens in an
earthen pond and feeding either a 35 percent protein

containing 2.5 percent squid meal, 40 percent pro-
tein containing 5 percent squid meal, 45 percent pro-
tein containing 10 percent squid meal, or 45 percent
protein containing 15 percent squid meal feeds at a 4
percent feed rate (Table 6). Similar to the previous
data, none of the treatments differed significantly.
Growth rates were 2.29 to 2.45 g/week, and harvest
biomass levels were 6,296 to 6,989 kg/ha. These data
indicate that a much lower feed quality can be con-
sidered for shrimp production levels of as much as
5,000 to 6,000 kg/m’. Of significance is the fact that
the treatment containing unfed shrimp in pens in the
same pond had a harvest biomass production level of
more than 50 percent of the production level in the
fed treatments.

Table 6. Data on Penaeus vannamel fed practical feeds contain-
ing 35/2.5, 40/5, 45/10, and 45/15 protein squid levels. Each value
represents a mean of 12 observations.

Parameter Unfed Protein/squid level in feed
shrimp 35/2.5 40/5 45/10 45/15
Growth rate 0.79 2.29 2.42 2.45 2.30
(s/Weflk)
Survival 88.0 89.4 77.5 83.9 83.8
(%)
Harvest size 10.50 19.6 20.3 20.5 19.6
(g/shrimp)

Harvest biomass 3,696 6,989 6,296 6,876 6,578
(ks/ha)

Demonstrated that growth and production
of Penaeus- vannamei in earthen ponds were
2.19 g/week and 6,232 kg/ha with 13 mg vitamin
C per kg of the feed and 2.22 g/week and 6,288
kg/ha with 246 mg vitamin C per kg of feed.

Three experiments were conducted using Penaeus
vannamei. The first two experiments were feeding
trials conducted in the laboratory under highly con-
trolled conditions and in the absence of natural pro-
ductivity. The third experiment was a feeding trial
conducted in pens in an earthen pond in the pres-
ence of two potential food sources: presented feed and
natural productivity.

In the first laboratory experiment, small shrimp
having an initial body weight of 226 mg were fed
semipurified diets containing 0, 25, 50, 75, 100, and
1,000 ppm of a protected form of vitamin C, L-
ascorbyl-2-polyphosphate (APP). After 14 days, the
survivals were 23, 36, 50, 52, 63, and 91 percent for
shrimp fed semipurified diets containing 0, 25, 50,
7 5, 100, and 1,000 ppm vitamin C, respectively. These
data indicate that the vitamin C requirement was
more than 100 ppm but probably less than 1,000 ppm
in the feed. In the second laboratory experiment,
larger shrimp having an initial body weight of 900

mg were fed the same semipurified diets containing
50, 75, 100, and 1,000 ppm vitamin C levels. Aflaer 2
weeks, the survival of shrimp fed diets containing 50
and 75 ppm vitamin C (39 and 57 percent, respec-
tively) were significantly less than survival of shrimp
fed diets contain 100 and 1,000 ppm vitamin C (89
and 96 percent, respectively). These data indicate that
shrimp are highly sensitive to vitamin C deficiencies,
that the protected form of vitamin C L-ascorbyl-2-
polyphosphate (APP) is available to shrimp, and that
vitamin C dietary requirements change with age (He
and Lawrence 1993).

Forty Penaeus vannamei/m’ having an initial
weight of 5.81 g were stocked into l-m’ pens in an
earthen pond for 42 days. Practical feeds were for-
mulated to contain 0, 75, 150, and 250 ppm vitamin
C (APP) and were analyzed to contain 13, 100, 153,
and 246 ppm vitamin C. At the end of the experi-
ment, no treatment differed with respect to growth
(1.88 to 1.98 g/week), final body weight (18.9 to 19.7
g/shrimp), survival (80.2 to 83.1 percent), and har-
vest biomass (6,120 to 6,370 kg/ha) (Table 7). There
was no difference in vitamin C level (50 to 54 ppm) in
tissues of shrimp fed practical feeds containing 13 to
153 ppm vitamin C, although the level of vitamin C
in tissue of shrimp fed the practical feed containing
246 ppm was significantly higher (66 ppm). The nu-
tritional contribution to the shrimp from natural pro-
ductivity was estimated to be about 33.8 to 35.1 per-
cent. These data indicate that for these conditions
and for harvest biomass levels of as much as 6,000
kg/ha, no vitamin C is required in the prepared feed
(Robertson et al. 1992d). Initial biomass of shrimp
stocked into pens was equivalent to 2,324 kg/ha.

Table 7. Data on Penaeus vannamel fed practical feeds contain-
lng 13, 100, 153, and 246 ppm vitamin C levels. Each value repre-
sents a mean of 12 observations.

Parameter Unied Analyzed vitamin C level in ppm

shrimp 13 100 153 246
Growth rate 0.79 2.19 2.32 2.24 2.22
(ti/Week)
Survival 88.0 82.3 80.2 83.1 82.3
(%)
Harvest size 10.50 18.9 19.7 19.2 19.1
(Qlshfimp)

Harvest biomass 3,696 6,232 6,320 6,382 6,288
(ks/ha)

‘Pond biomass 1,372 3,908 3,996 4,058 3,964
increase (%)

“Contribution 35.1 34.3 33.8 34.6

(%)

' Harvest biomass minus initial biomass (2,324 kg/ha) in kg/ha.

“Increase in pond biomass of unfed treatment divided by increase in
pond biomass of a fed treatment times 100.

Disease

Demonstrated that N ecrotizing Hepatopan-

’\ creatitis (NHP) and Texas Pond Mortality Syn-

drome (TPMS), synonym Granulomatous
Hepatopancreatitis (GH), do not appear to be
correlated to the presence of inclusions, and
hence IHHNV does not cause this syndrome.

Six or more shrimp were collected from various
commercial ponds and at different selected times
during the culture period and were processed. Four
sections were prepared from each shrimp: a sagittal
section of the cephalothorax, a section of the gills, a
cross section of the third abdominal segment, and a
sagittal section of the sixth abdominal segment.
Analysis of these tissues indicated that hepatopan-
creatic granuloma formation did not appear to be cor-
related to the presence of inclusions; hence IHHNV
does not cause N HP.

Determined that use of oxytetracycline
(OTC)-medicated feed markedly increased the
harvest biomass in 1990 (6,569 kg/ha) compared
with that of 1989 (881 kg/ha) and 1988 (1,025 kg/
ha) on a commercial shrimp farm in Texas.

Necrotizing Hepatopancreantitis (NHP) has re-
duced production of shrimp in ponds in Texas since
1985. Recently, a rickettsia-like organism was pro-
posed as the etiologic agent of NHP (Frelier et al.
1992). Previous diagnostic reports from the Texas Vet-
erinary Medical Diagnostic Laboratory in 1988 and
1989 verified that TPMS was present in the ponds of
a commercial farm at the time mortalities were ob-
served. In 1990, when TPMS was initially observed
in ponds of the same commercial farm, a field trial
using oxytetracycline (OTC)-medicated feed was ini-
tiated. This research was conducted in cooperation
with Tom Bell from the University of Arizona. The
USDA (via the Center for Tropical and Subtropical
Aquaculture) sponsored the FDA-approved experi-
mental testing of OTC-medicated feeds. The medi-
cated feed was fed for 10 to 14 days. Aminimum with-
drawal period of 15 days before harvest was included
in the protocol. For the 30 treated ponds in 1990, the
average harvest biomass was 6,569 kg/ha with a sur-
vival of 44.5 percent. In 1989, 15 of these same ponds
had an average harvest biomass of 881 kg/ha with a
survival of 11.4 percent. For 1988, 20 of these same
ponds averaged a harvest biomass of 1,025 kg/ha with
a survival of 24.5 percent. These data indicate that
the harvest biomass and survival of ponds contain-
ing shrimp with TPMS may be increased with the
use of OTC-medicated feed (Bell et al. 1992, Bell and
Frelier 1991).

Development of High-Quality
Shrimp Populations

Demonstrated that a harvest biomass of
4,003 to 4,288 kg/m’ and 2,443 to 2,578 kg/m’ with
a growth rate of 0.93 to 1.04 and 0.69 to 0.76 g/
week was obtained with Penaeus setiferus and
Penaeus aztecus in earthen ponds.

Penaeus setiferus (3.4 g mean weight), P. aztecus
(7.4 g mean weight), and P. vannamei (6.9 g mean
weight) were stocked at a density of 40 shrimp/m”
into 1-m2 pens in an earthen pond for 56 days
(Robertson et al. 1992c). The shrimp were fed either
a 30, 40, or 50 percent protein feed. The mean salin-
ity and minimum and maximum temperatures were
32.4 ppt and 26.8 and 31.4 °C, respectively. The P.
setiferus postlarvae, produced at Waddell Mariculture
Center in South Carolina in captivity, were shipped
to Texas A&M University. The P. vannamei PL pro-
duced by a commercial hatchery in Texas were
shipped to Texas A&M University. Both of these spe-
cies then grew to stocking size at Texas A&M Uni-
versity. P. aztecus was obtained from Corpus Christi
Bay and acclimatized to pond conditions for a mini-
mum of 1 week before stocking the pens. Thus, the P.
setiferus and P. vannamei were from a laboratory
source, whereas P. aztecus were from a natural source.

As seen in Table 8, Penaeus aztecus has a lower
growth rate, survival, weight gain, and harvest bio-
mass than do P. setiferus andP. vannamei (Robertson
et al. 1992c). The growth rate and weight gain of R
setiferus and P. vannamei are similar, but the sur-
vival rate of P. setiferus is greater than that of P.
vannamei. The greater harvest biomass of P.
vannamei than P. setiferus is due to the much larger
initial size of P. vannamei (6.9 g/shrimp) than that of
P. setiferus (3.6 g/shrimp). The P. vannamei used in
this experiment were of low quality.

These data indicate that of the native species
Penaeus setiferus is much more productive than P.
aztecus under pond conditions. For the conditions of
this experiment, the data indicate that P. setiferus
can be considered for pond culture in Texas because
growth was similar and survival was better than for
a low-quality population of P. vannamei. The data
obtained in other experiments using higher quality
P. vannamei yielded much greater growth and pro-
duction values for P. vannamei than the growth and
production values of P. setiferus obtained in this
experiment.

Table 8. Data on Penaeus setiferus, P. aztecus, and P. vannamei fed 30, 40, and 50 percent protein feeds. Each value represents a mean

o1 12 observations.

Parameter R setifems R aztecus R vannamei
30% 40% 50% 30% 40% 50% 30% 40% 50%

Stocking size 3.6 3.6 3.6 7.4 7.4 6.9 6.9 6.9
(st/shrimp)

Growth rate 0.93 1.01 1.04 0.69 0.76 0.97 1.04 1.07
(g/week) I

Survival 90.4 90.8 90.0 47.3 49.8 47.3 78.5 82.7 80.6
m) p

Weight gain 7.5 8.1 8.3 5.5 6.1 7.7 8.3 8.5
(g/shrimp)

Harvest biomass 4,003 4,224 4,288 2,443 2,578 2,554 4,603 5,031 4,984
(ks/ha)

Demonstrated that growth and survival
rates were similar for Penaeus setiferus and
Penaeus vannamei fed 28 percent protein feeds
in earthen pond culture.

Penaeus setiferus (1.5 g mean weight and initial
densities of 15 and 30 shrimp/m’) and P. vannamei
(0.7 g mean weight and initial density of 15 shrimp/
m2) were stocked into l-m’ pens in an earthen pond
for 28 days. The shrimp were fed one of three differ-
ent 28 percent protein feeds of three different pro-
tein qualities as represented by 100 percent animal
protein, 50 percent animlal and 50 percent plant pro-
tein, and 100 percent plant protein. The data in Table
9 indicate that all three protein-quality feeds are ad-
equate when the shrimp are stocked at 15 shrimp/
m’. However, when the density for P. setiferus is in-
creased to 30 shrimp/m’, the growth of shrimp fed
feed containing 100 percent plant protein is signifi-
cantly less than of shrimp fed feeds containing 100
percent animal protein or 50 percent animal protein
and 50 percent plant protein. Growth and weight gain
is slightly less but survival is slightly greater in P.
setiferus than P. vannamei. Harvest biomass of P.
setiferus is larger compared with P. vannamei because
the initial stocking weight of P. setiferus was larger

than of R vannamei. The growth rate, survival, and
weight gain of P. setiferus is lower at the initial stock-
ing density of 30 shrimp/m’ versus 15 shrimp/m”.
Again, the data indicate that P. setiferus can be con-
sidered for pond culture in Texas because its growth
rate and survival are similar to P. vannamei for the
conditions of this experiment. It must be noted that
data obtained in other experiments using higher qual-
ity P. vannamei yielded much greater growth and
production values for P. vannamei than growth and
production values for P. setiferus obtained in this ex-
periment (Lawrence and Houston, 1992).

Developed a method for evaluating Penaeus
vannamei postlarvae (PL) quality and obtained
data indicating that the lower the postlarvae
quality, the lower the growth rate in the nurs-
ery phase.

Four- to eight-day-old PL from two different popu-
lations of Penaeus vannamei broodstock were ob-
tained from a commercial hatchery in Texas. One
population, designated lower quality (LQ), was pro-
duced from a commercial broodstock cultured through
several generations at the hatchery and was identi-
fied as having the presence of IHHNV (Infectious
Hypodermal and Hematopoietic Necrosis Virus). The

Table 9. Data on Penaeus setiferus and R vannamei fed 28 percent protein feed consisting of either 100 percent animal protein (ani), 50
percent animal protein, and 50 percent plant protein (alp) or 100 percent plant (plt). Each value represents a mean of eight observa-

tlons.
Parameter R vannamei15/m2 R setiferus 15 m2 R setiferus 30 m’
ani a/p pit ani a/p plt ani a/p plt

Stocking size 0.7 0.7 0.7 1.5 1.5 1.5 1.5 1.5
(g/shrimp) .

Growth rate 1.30 1.30 1.25 1.10 1.08 1.00 1.00 0.83‘
(g/week)

Survival 80.4 75.3 77.0 88.1 93.7 88.3 79.2 72.8 71.3
(%) '

Weight gain 5.2 5.2 5.0 4.4 4.3 4.0 4.0 3.3
(g/shrimp)

Harvest biomass 690 666 655 830 850 799 1 .306 1,205 1,029
(kg/ha)

‘Value is significantly less (P < 0.05) than for respective values of shrimp fed either all animal protein or 50 percent animal protein and 50 percent

plant protein.

other population, designated higher quality (HQ), was
produced from broodstock from the Oceanic Institute
in Waimanolo, Hawaii. Repeated histologic examina-
tion of the HQ animals failed to identify evidence of
Hepatopancreatic Parvo-like Virus (IHHNV), HPV,
Baculovirus Penaei (BP)-type baculovirus, micro-
sporidians, gregarines, and nematodes or cestodes.
All postlarvae were produced simultaneously using
identical culture conditions and methods. Four
batches were obtained from each of the LQ and HQ
populations. Each batch was stocked into one 2.4-m-
diameter tank (5,000 PL/tank) and eight 28-cm-di-
ameter tanks (20 PL/tank). No survival differences
were noted, but the PL from the HQ population grew
faster than the PL from the LQ population. An addi-
tional growth trial on juvenile shrimp indicated that
the differences observed in PL growth between the
two populations continued to be expressed during
juvenile growth. Correlations of PL growth to larval
duration and survival suggest that larval survival was
a good indicator of PL quality but that time required
for larval development (from nauplii to PL) was in-
adequate to predict growth.

These data indicate that a 14-day growth trial
using 4- to 8-day-old PL can be used to predict the
quality of PL produced in the hatchery and that the
quality of PL is important in determining the growth
rate of shrimp (Castille et al. 1993).

Developed husbandry practices for main-
taining specific pathogen-free (SPF) brood-
stock to produce SPF postlarvae for market-
able-size shrimp in ponds.

The following husbandry practices for maintain-
ing SPF broodstock to produce SPF postlarvae (PL)
for marketable-size shrimp in ponds were developed
and applied. SPF is defined as free of IHHNV, HPV,
BP-type, microsporidians, gregarina, nematodes,
and cestodes.

Prespawning

1. On the day of arrival and for the following 2 days
(first 72 hours), fix all but the first moribund ani-
mal in Davidson’s fixative for 36 to 48 hours and
then transfer them to 50 percent ethanol solu-
tion. Each bottle contains only one animal and is
labeled with the time and date each animal was
killed. Fixation includes injecting each animal
with fixative at multiple sites and then making
two longitudinal cuts along the side of the cuticle
before the animal is immersed into a bottle of fixa-
tive. The ratio of tissue to fixative should be kept
to 1 part shrimp to 10 parts fixative. Proper fixa-
tion is imperative to demonstrate the intranuclear
inclusions of IHHNV.

2. Dry the first moribund animal with paper towels
and freeze it. This animal should be double-
bagged and if possible, placed into a freezer that
has never contained shrimp tissue.

3. At the end of the initial 72-hour period, take
samples from 27 additional animals (not count-
ing the frozen animals). This represents a total
sample of 27 animals in addition to the moribund
animals collected. It is recommended that six
expendable animals be chosen to test the ampu-
tation and cauterization technique. The sample
size of 27 is used because 27 corresponds to the
number of samples needed to detect at least 1
infected animal in a population of 500 with an
assumed pathogen prevalence of 10 percent. The
pereiopods may be fixed and stored in one or two
bottles as long as each pereiopod is from a single
animal.

4. Kill all moribund animals found before they
spawn and fix and process them as in step 1.

5. The week before spawning commences, sacrifice
three animals; fix and process them as in step 1.
This sample size was determined because it rep-
resents the number of shrimp that must be
sampled to detect at least 1 affected animal in a
population of 500 when 50 percent of the popula-
tion is affected. It is assumed that the population
was originally SPF and naive to IHHNV, and if
infected, then at least 50 percent of the popula-
tion should become infected.

6. Individually fix and label with the date killed all
moribund animals found during the spawning
period.

Postspawning

7. At the end of the spawning period, fix 60
broodstock in Davidson’s fixative. Included in this
number will be all the animals that had under-
gone amputation of the pereiopod during the first
3 days of arrival. a

8. From each larval tank, fix approximately 600 to
700 5- to 7 -day-old PL in Davidson’s fixative.

9. At the end of each nursery period, kill and fix 30
animals from each lot.

10. At the end of the grow-out period, kill and fix 30
animals from each pond stocked with SPF PL’s.

Specific Husbandry Procedures

11. Receive the broodstock as late as possible in the
year before they spawn, but allow for acclima-
tion.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

Use a “clean” vehicle, which has not been used
for any farm work the preceding week, for trans-
porting the shipment.

Individuals handling the shipment should not
have been on the farm that day. If they have, they
must return home, shower, and change clothes
before receiving the shipment.

Wipe off the boxes containing broodstock with al-
cohol or an iodophor (e.g., Betadine) before load-
ing into the vehicle and again before entering the
hatchery room.

Use automatic feeders for night and day feeding,
thus eliminating a night worker and reducing
labor during the day.

Change foot baths (200 ppm minimum chlori-
nated water) in the SPF areas at least once every
third day.

Make specific individuals responsible for the SPF
broodstock.

Perform as many duties as possible concerning
the broodstock first in the morning, before people
contact infected areas.

Prepare food for the SPF broodstock before that
of other broodstock, and keep the feed separate.
These facilities should be as clean as possible and
wiped down with a suitable disinfectant afizer use.
Keep a segregated final feed storage area for the
broodstock.

Use only pasteurized shrimp products in the feed
unless experimental data indicate otherwise.

Wall off the broodstock tanks with a plastic bar-
rier about 1 foot below the overhead lights. Weigh
down the bottom and seal with silicone.

Allow only one entrance to the broodstock tanks
and a short hall serving as a dressing and wash-
ing room. Follow this sequence when entering the
broodstock area:

A. Wear a specific pair of boots, assigned to no

one else, for work in the SPF broodstock area.
B. Walk through a foot bath.

C. Disinfect hands and arms with alcohol or an
iodophor.

D. Put on a long surgery/laboratory gown having

elastic cuffs.
E. Put on gloves and wash hands.

Wash the floors of the SPF area weekly with dis-
infectant after the adjacent contaminated areas
are cleaned.

10

24.

25.

26.

27.

28.

29.

30.

. Examinations to date suggest that the three com-

Spawn the SPF animals (iflpossible) before other
stocks. 

Give the SPF stock a separate spawning room
and/or a movable partition that can be used to
isolate spawning tanks.

Provide SPF stock an isolated “hatching room”
with a foot bath at the entrance.

House SPF larvae in a semi-isolated area of the
building, preferably as far from the contaminated
area as possible. Plastic “drapes” can be hung to
isolate these tanks. Provide at the entrance to
the tanks a cleaning station.

Perform maintenance of the larval tanks before
coming in contact with contaminated tanks.

Before each use, disinfect and wash the final
tanks used to count and acclimate PL’s and the
truck tanks for transport to the pond.

When possible, designate equipment used on the
SPF stock for that stock.

Results

. Examinations to date indicate that the husbandry

recommendations instituted were sufiicient to
maintain SPF broodstock, including those free of
IHHNV infection, for the production of SPF PL’s.

mercial production ponds initially stocked with
SPF PL’s are either free of IHHNV infection or
that the prevalence of infection is below the level
detected by histological methods.

Reviews

Four published reviews are also noteworthy.

Learning to Determine Quality (Bray and Lawrence

1992) reviews new concepts in seedstock production.
The second discusses penaeid larviculture using the
“Galveston Method” (Smith et al. 1992a). The third
is about the use of 1-L Imhoff cones to optimize
larviculture production (Smith et al. 1992b). The
fourth reports on reproduction of penaeid shrimp in
captivity (Bray and Lawrence 1992).

Summary

Major accomplishments reported in this review

are as follows:

1.

Penaeus vannamei production in tanks without
substrate and lined ponds is equal to or better
than production in tanks containing either sand €
or clay substrate and unlined ponds.

2.

10.

11.

12.

13.

P. vannamei production in outdoor tanks in-
creases as salinity decreases from 49 ppt to 5 ppt.

. Growth better than 2 g/week was obtained in P.

vannamei for at least one treatment in six ex-
periments conducted either in outdoor tanks or
pens in earthen ponds.

. Intensive round pond technology developed by

Oceanic Institute was transferred to Texas, and
intensive production (growth rates of 1.82 to 1.90
g/week with harvest levels from 7,229 to 9,107
kg/ha) of P. vannamei in square ponds was simi-
lar to round ponds having a bottom area of about
0.07 to 0.1 ha.

. Technology was developed for production of 0.5-

to 0.8-g juvenile P. vannamei in raceways with
survival rates of 91 to 99 percent and production
of 14,200 and 18,900 kg/ha, at initial stocking den-
sities of 3,100 to 3,300 PL/m“.

. New technology was developed for removing

waste and for aerating and circulating water for
nursery raceway production of R vannamei; more
than 7,000 juvenile P. vannamei PL/m’ were suc-
cessfully produced with a minimum survival rate
of 92 percent and a food conversion ratio (FCR)
of about 0.6 in raceways.

. Technology was developed for producing 6.5- to

8.1-g P. vannamei in raceways with survival of
78 to 83 percent and production of 13,600 to
15,600 kg/ha, at an initial stocking density of 233
or 299 PL/mz.

. The lower growth of P. vannamei at high salini-

ties of 46 ppt can be improved by increasing the
protein level of the feed.

. P. vannamei obtained some of their requirements

for minerals from the substrate and seawater, the
substrate being more important than seawater.

Growth (2.31 to 2.22 g/week) and production
(6,608 to 6,636 kg/ha) were similar for constant
feed rates of 4, 6, and 8 percent body weight per
day but were greater than a constant feed rate of
2 percent body weight per day (1.70 g/week and
5,912 kg/ha) for P. vannamei in pens in earthen
ponds.

Experiments conducted in pens in earthen ponds
suggest that P. vannamei fed during the day grew
as fast as shrimp fed at night.

Experiments conducted in pens in earthen ponds
indicate that growth of P. vannamei increased as
feeding frequency increased from one to four times
per day.

Growth (2.09 g/week) and production (6,723 kg/
ha) when P. vannamei in pens in earthen ponds

11

14.

15.

16.

17.

18.

19.

20.

21.

22.

were presented a 25 percent protein quality feed
was not significantly different when P. vannamei
were presented a 45 percent protein quality feed
(2.31 g/week and 6,606 kg/ha).

P. vannamei fed a commercial feed containing 35
percent protein and 2.5 percent squid meal had
similar growth (2.29 gm/week) and production
(6,989 kg/ha) rates to those presented a feed con-
taining 45 percent protein and 15 percent squid
meal (2.30 g/week and 6,578 kg/ha) in pens in
earthen ponds.

Growth and production of P. vannamei in pens in
earthen ponds were 2.19 g/week and 6,232 kg/ha
with 13 mg vitamin C per kg of feed and 2.22 g/
week and 6,288 kg/ha with 246 mg vitamin C per
kg of feed.

Necrotizing Hepatopancreatitis (NHP) and Texas
Pond Mortality Syndrome (TPMS), synonyms
Granulomatous Hepatopancreatitis (GH), do not
appear to be correlated to the presence of inclu-
sions, and hence IHHNV is not the etiology of this
syndrome.

The use of oxytetracycline (OTC)-medicated feed
markedly increased the harvest biomass in 1990
(6,569 kg/ha) compared with those of 1989 (881
kg/ha) and 1988 (1,025 kg/ha) on a commercial
shrimp farm in 'I‘exas.

A harvest biomass of 4,003 to 4,288 and 2,443 to
2,578 kg/m2 with a growth rate of 0.93 to 1.04
and 0.69 to 0.76 g/week was obtained in P.
setiferus and R aztecus in pens in earthen ponds.

Similar growth and survival was obtained in P.
setiferus and a low-quality population of P.
vannamei fed 28 percent protein feeds and cul-
tured in pens in an earthen pond.

A method was developed for evaluating P.
vannamei postlarvae quality, and data indicate
that the lower the quality of the postlarvae, the
lower the growth rate in the nursery phase.

Husbandry practices were developed to maintain
SPF broodstock for SPF and subsequently for
production of marketable-size shrimp in ponds.

Seedstock quality and evaluation methods,
penaeid shrimp hatchery production, raceway
production, and an experimental system for opti-
mizing shrimp hatchery systems using Imhoff
cones have been reviewed.

A tremendous amount of new technology has been

developed during the last 3 years. However, commer-
cial shrimp culture in Texas is still marginal. Addi-
tional technology is needed for intensification of race-
way and pond culture, feeds and feeding strategies,

disease prevention, and development of high-quality
shrimp populations.

Acknowledgments

This research was funded in part by grant num-
ber H-6028 from the Texas Agricultural Experiment
Station, Texas A&M University System, and by the
U.S. Department of Agriculture, Cooperative State
Research Service, grant no. 88-38808-3319 for 1989
to date.

The research reviewed in this paper was also done
in cooperation with four companies involved in shrimp
culture: Harlingen Shrimp Farm, Los Fresnos, 'I‘exas
78566; Wolf Point Shrimp Farm, Port Lavaca, Texas
78979; Rangen Feeds, Inc., Buhl, Idaho, 83316; and
Gundle Lining Systems, Inc., Houston, Texas 77073.
The cooperation and support of these companies are
gratefully acknowledged.

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12

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