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Thesis
Twork, Elton C
The rernoval of be aver dams
from Michigan t rout
and some Other Condi
effecting the trout
rºle...t.


THE REMOVAL OF BEAVER DAMS FROM MICHIGAN TROUT STREAMS,
AND SOME OTHER CONDITIONS EFFECTING THE TROUT ENVIRONMENT
* * *k ºr ºr ºf x * * * * * *
* Elton C. Twork
School of Forestry & Conservation
University of Michigan
Table of Contents
Introduction -- - - - - Page 1
Destruction of Beaver dams and the effect
upon the stream - - - - - - - - - - - - 3
Erosion of Soil due to Beaver dams - - - - 8
The Destruction of dams still in use - - - 10
Part II.
SOME PHYSICAL AND CHEMICAL CONDITIONS EFFECTING
THE TROUT ENVIRONMENT
Fresh-water fishes require a certain degree of acidity
to carry on their normal activities — — — — — — — —
The Effect of the pH values of the water on the
Changed Stream conditions following Logging and Fire
Further Investigations needed — — — — — — — — — — — — -
Conclusions - - - - - * * * * * * * * * * * * * * * * *
Recommendations for Stream Improvement — — — — — — — — —
References cited — — — — — — — — — — — — — — — — — — — —
Page
12
THE REMOVAL OF BEAVER DAMS FROM MICHIGAN TROUT STREAMS
Today with conservation programs of all kinds being enacted
the fisherman of the country have demanded that something shouli.
be done to improve the conditions in our trout stream tº cº-mars’
better fishing. Because the planting of hatchery fish hºe not
made good fishing, the possibility of improving the streams them –
selves to make stream conditions more suitable to the fish life
has *1%. What can be done to make our streams self sustain-
AX _-_G=-
ing, that a trout stream may always be a good trout stream?
This is a question with which the conservation authorities have
had to deal.
To answer this question, many methods of stream improve –
ment are being tried out . At present, beaver dams are being
removed from streams without taking into consideration the
individuality of each stream. A generalization has been made
that be aver dams are deleterious to trout streams; so, they
should be removed. It is this method and its effect upon
our trout and be aver that I would like you to consider with me .
The general plan as carried out in State C. C. C camps is
that a project is planned for each camp by the district super-
visor of stream improvement. The streams that are to be worked
upon by a camp are submitted to the Conservation Department at
Lansing for approval by the fish division. Upon approval, the
project is allotted a certain number of man-days, and sent to



the camp superintendent, who starts a crew of man to work on
the project with the help of the district supervisor of stream
improvement. Because the district supervisor cannot always be
on hand to help, it is necessary that the foreman on the job
have a knowledge of the work he has undertaken to do, if he is
to do a good job.
Because most of the devices constructed to improve the
stream do some good or at least do very little harm, the problem
of how to install the se devices is not as vital alsº, the question,
"when and where should beaver dams be removed?"
The removal of be aver dams from our trout streams without know-
ing the needs of the stream and the conditions as they exist,
has in many cases been harmful to both trout and be aver.
In the past, there have not been enough trained men to
supervise the work in stream improvement, the supervisor had
to look after the work in an area which was too large for him
to handle efficiently; and generally, the foreman on the job
knew very little about the work. Thus to get the dams removed
which were believed to be doing damage, without the help of a
“emeytraine. man on the job, the generalization was made
that all beaver dams are harmful to the stream and should be
removed. As a result many dams were destroyed, doing more
harm than good to the trout stream, and at the same time
destroying the homes of the be aver.
THE DESTRUCTION OF BEAVER DAMS, AND
THE EFFECT UPON THE STREAM
In order to show the effects of removing beaver dams
upon the trout environment, it is necessary to describe
conditions as they existed before the dam was removed.
In the first instance, (Dam No. 1), the beaver had selected a
site for their dam where the ravine in which the stream
flowed was only about 150 feet wide; the stream at this point
being 12 feet in width, and having an average depth of one
foot. The dam had been built several years previously, and
was now four feet high and three feet wide on top. With the
creation of a pond the dam had to be widened until it had
reached a length of about 125 feet. The dam was well plastered
with mud so that it leaked very little; the Water leaving the
pond had to flow over the top of the dam. The water impounded
by the dam covered an area of about two acres, and the stream
was deepened over a distance of 800 feet above the dam.
For a distance of fifty feet above the dam, mud had been dug
from the bottom of the stream to plaster the dam, and this
area of the pond was 6 feet in depth, the deepest part of the
pond.
The temperature of the water in the pond, taken just above
the dam, was 60°F in July.
The dam was opened at the point where the old stream bed
had been to a width of twelve feet. When the water had gone
down to normal, the small puddles, which were isolated from
the main stream, were dipped out to see if any fish had
been trapped. Two speckled trout, six inches long were
found. In most puddles small minnows were numerous, and
many lamphreys, 2 to 6 inches long were found in the mud.
All the area, that had been flooded was covered with a
heavy deposit of black mud. The pond remaining was only
that portion which had been dug out to plaster the dam.
The stream above the pond had become very shallow,
being only about 6 to 8 inches deep. Sand was being washed
down stream filling in the pond. There was very little
cover for trout in that portion of the pond that was left,
and the stream above, for a distance of 800 feet, had
shrunk from a width of twenty feet to one of ten. The
tag-alders, which before had offered some protection to
the fish and shade to the stream, were now several feet
from the edge of the water.
The stream above that portion directly affected by the
be aver dam is well shaded and contains numerous small holes
and plenty of cover in fine form of logs and fallen trees
for the trout to hide under, although this portion of the
stream is generally considered too shallow for trout to
over-winter in. Further up stream about a mile, a large
dam was removed earlier in the season, and the stream above
has become so shallow that the stream had dried-up between
holes during the dry season.
The removal of the dam, which was in the upper course
of the stream, shows very little benefit to the stream.
Temperature conditions of the water taken several weeks
after the removal of the dam show this portion of the stream
to be warmer than further down stream, where the maximum
temperature reached was 56 F. This condition was probably
due to the greater number of cold springs that were found
further down stream. The slight warming effect of the
be aver pond on the stream, instead of being injurious to
the stream below, rather, ameliorated the temperatures of
the stream below for better trout growth. *
The purpose of removing the dam to allow free passage of
fish during spawning season was not sound, as their were few
places above where spawning conditions were satisfactory.
This was due mainly to the scarcity of gravel beds, and because
the stream was very much subject to seasonal changes.
The fact that trout were caught in the pond in the spring,
and that some trout were seen when the dam was opened, was
evidence that the pond was still inhabited by trout. This
pond, because it was fed partially by spring water frºm, the
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nearby hills, and because it was deep, was, Swith probility, 6
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a wintering pond for many trout which retreated from the
shallower waters above. The pond also acted as a settling
basin for silt which would have otherwise gone down stream
where its effects might be more injurious. Although there
was a heavy accumulation of black mud in the bottom of the
pond, the water was cool enough, and there was enough water
running in and out of the pond, that the pond did not
become stagnant. It is well known that be aver ponds are
fertile fields for the production of trout food. Destroy-
ing the pond, eliminated an important source of food, thus
decreasing the number of trout the stream can maintain.
Before any be aver dam is destroyed, the purpose for
which it is to be removed must be kept in mind. The purpose
is usually one or all of the following:
1. TO allow free passage of fish in spawning season.
2. To remove the warming or cooling effect of the
be aver pond and dam.
3. To prevent stagnation of the water and improve the
pH condition of the stream , .
Having these purposes in mind, consider the location of the
dam on the stream, and if its removal will bring about the
results desired.
AS another example, let us consider dam No. 2. This
dam was located in a small soft-bottom stream about a
quarter of a mile from where it emptied into a larger river
which contained brook, brown and rainbow t rout . The branch
stream is about seven miles in length. The source of the
stream is a marsh. The stream has cut its way through the
pine plains, and now lies in a "flats" which is three hundred
to a thousand feet wide, and covered with a dense growth Of
tag-alder, spruce and cedar.
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This dam had been built where the stream was about
fifteen feet wide. With the rising of the water the dam
was increased in height and length until it was now four
feet high and one hundred-sixty feet in length. It was an
old dam which the beaver were repairing, and had caused an
area of about an acre to be flooded. The main stream channel
was three to six feet deep and it contained some holes which
were deeper. Upon examining the bottom, it was found not to
be as heavily silted as is usually the case of old be aver
ponds. This was probably due to the fact that repairs on
the dam were recent and much of the water had been escaping.
The dam was torn open to the width of the old stream,
and after the water had gone down to normal, it left the
stream channel above where the dam had been with a depth of
one to three feet of water.
Within a mile further up stream were four major dams,
and twelve secondary dams. These were all removed, and four
days later the temperature of the Water was taken at the place
where the first dam was removed, and it was found to have
dropped from 57° F (temperature before dam was removed) to
55°F.
The main objective for removing these dams was to allow
free passage for trout going up stream during the spawning
season, and to allow the larger trout to go down into the
larger stream at other seasons, where they can find a hab-
it at more to their liking. In this way the small stream
would act as a nursery stream to stock the larger river
with legal size trout, and at the same time give the large
cannibal trout a chance to get out of the smaller nursery
stream.
Beaver dams cause damage, in many cases , other than to
the stream it self. However, these cases can usually be
remedied without destroying the home of the be aver, and
as the number of dams destroyed because of these damages
is small as compared to the dams destroyed in stream
improvement projects, these damages will not be asseursea.
There is, on the other hand, a condition where beaver dams
have caused a great amount of damage to both the stream, and
the surrounding land.
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The erosion of soil caused by be aver dams in streams
which flow through sandy regions has caused much damage to
the trout environment. As a result of having their bottoms
covered with a layer of yellow sand, many stream” which Were
formerly good trout streams have become barren of trout.
The sandy bottom is not productive of trout food, as most
of the organisms upon which trout feed need larger and
stationary objects upon which to cling in order to grow
and reproduce. Even where there are places that the swift-
ness of the current keeps stones and other objects exposed,
the action of the drifting sand along the bottom of the
stream kills: 'much of the in sect life.
As an example of how be aver cause erosion and the
resulting "sanding" of the stream, let us consider Dam NO. 3.
This dam was located in the upper course of a large trout
st Team. The dam had been built where the stream was about
thirty feet wide, and where it ran next to a sand bank about
fifty feet high. The dam was four feet high and three feet
wide on top. The bank opposite the sand hill is about six
feet higher than the normal level of the water, so that the
dam did not create the usual wide beaver pond, but caused
the stream above to be deepened for a distance of 500 feet
up stream from the dam. The deepening of the water and the
working of the beaver under the banks, in which they lived,
caused much of the bank above the dam to break off, t and
the pond became heavily sanded; where as before it had a
hard bottom of gravel.
During the high water in the spring, a hole had been
washed-out around the end of the dam next to the sand bank,
causing more of hillside to fall into the stream. That this
had happened was evident by the large cut made into the bank
at this point, and that the material of the dam at that end
was still fresh. It is probable that wash-outs of this
nature occur each spring, especially where heavy spring
thawings of snow occur on sparsely timbered and burned-over
lands.
10.
Further up stream, within two miles of the latter dam,
Were two similar cases. Irl both places the dam had been
built at the base of a large sand hill. In the one case,
the end of the dam next to the hill had been washed out,
and never repaired. The remaining part of the dam was now
acting as a deflector, throwing the full force of the current
against the base of the hill. The washing away of the base
of the hill was causing the hill-side to drop into the stream,
and for 70 feet up the hill-side , which now had a slope of
about 45 degrees, there was nothing but rolling sand, and
wind erosion had already begun.
In the other of the two cases last mentioned, the dam
had been repaired again and again. Erosion of the hill-side
had already proceeded to the top of the hill. Here large
pieces of hard-pan had broken off and rolled to the base
of the hill and into the stream. This material was not act-
ing as a barrier to keep the sand from rolling into the
stream and, at the same time, protected the hill from further
Washing.
THE DESTRUCTION OF DAMS STILL IN USE
In most cases when a pond is destroyed which is being
used by beaver, it is only a few weeks before the pond is
again filled with water by repairing the old dam or the
construction of a new one. In the previous discussion of
dam No. 2, it was mentioned that above this dam were four
11.
major dams and twelve secondary dams, all of which were /
removed. One month after their removal , , all five major |
dams were found to be replaced either completely, or were |
in the process of being replaced. Dam No. 1, previously
described, was not rebuilt, but a new dam, larger than the
old one, was built in September about a thousand feet above
the Old site. Thus it can be seen that the work of remov-
ing beaver dams and trying to discourage beaver from build-
ing again is a futile task.
With the repairing of the old dams or the construction
of new dams, comes a great deal of excavation work by the
be aver. The beaver dig the dirt from the bottom and banks
of the stream to plaster the dam. The digging away of the
banks and bottom of the stream not only disfigures the stream,
but causes the water to be muddied, and much of the mud |
excavated is washed through between the sticks of the dam |
to be deposited on the stream bed further down stream.
Again, if the beaver do not repair the old dam and move to
a new site, the removal of the old dam has just shortened
the period over which the beaver would naturally inhabit
the old pond before the food supply gave out. It means,
that by removing such dams, we are only increasing the |
number of dams built on the stream during a period of years, ; :
thus increasing the number of places where the topography
of the stream will be altered.
12.
Part II.
Fresh-water fishes require a certain degree of acidity
to carry on their normal activities.
In a study made by Morris Miller Wells (13), it was found
that (a): fresh-water fishes are negative to neutral waters, and
in favor of either slight acidity or alkalinity. (b) Species of
fish differ in the degree of acidity selected, but that fishes
can tollerate very much higher concentrations of H ions than OH
ions. (c) The principal stimuli to which fishes react are H and
OH ions. There is no doubt but that fishes recognize the differ-
ences between very slightly acid or very faintly alkaline and
neutral water. Henderson's (4) work upon the mechanism which
maintains a constant proportion of H and OH ions in the blood
of animals, suggests the physiological reason for this extreme
sensitiveness of the fishes. It is clear that even very small
variations in the proportion of these two ions in the blood of
the organism, are of grave importance. and we find in the blood
3. combination of gasses and salts that make such variations
impossible as long as the animal is normal. The blood will
maintain its norman chemical reaction (just on the alkaline
side of neutrality) in the face of relatively large changes
in the environment, yet. We know that the mechanism breaks
down when the change is either too great or too long continued.
(Acclimination is not considered at this time.) The hyper-
sensitiveness of the animal to the chemical reaction of the
Water is another important factor in preserving the normal
reaction of the blood, as the reactions of the or ganisms
13.
Work in a Way that causes them to turn back from concen–
trations of H and OH ion that would be detrimental .
cºsmº
The Effect of the pH value of the Water on the
permeability of the Bills of fishes.
The physiological effect of the acid, neutral, and
alkaline water upon the organism very probably has to do
with decrease or increase in the permeability of the exposed
tissue cells (especially gills in the case of fishes).
Osterhout (7) has shown that in plant cells alkalies increase
the permeability up to death; acids, however, at first produce
a rapid decrease in permeability, followed later by an in-
crease which continues up to death. The concentrations of
acids used by Osterhout were .001 N. to .03 N.
Since fresh-water fishes are negative to neutral waters,
it is beleived that such water exerts a marked effect upon
the permeability, or some other physiological condition in
the gill membranes. Wells (13), states that the negativeness
of organisms to neutral Water indicates that they are either
over-stimulated in such Water, or under-stimulation sets up
internal disturbances, thus they may avoid it because of its
non-stimulating character. " It may be well that in neutral
water, the normal chemical reactions do not go on, for acidity.
and alkalinity surpass all other conditions in their influence
upon many chemical processes. Of all catalytic agents, H and
OH ions are by far the most important, and their influence upon
14.
the stability of colloidal systems are unapproached by
other substances. (Henderson '4).
Changed Stream Conditions Following Logging and Fire
That there has been a change in the water conditions of
many of our once good trout streams has often been pointed
out by the fisherman who have fished the se waters year after
year. They speak of the water as having a different color or
cast, and that the water now has a peculiar taste, whereas
before the se were absent. Some of the favorite stretches of
water along the stream were no longer yielding a catch, where-
as in another part of the stream, trout were plentiful. Many
of these fisherman believe that it is due to the destruction
of the forest S by lumbering and fire that has brought about
poor stream conditions, and that fishing will return with the
return of the forest Cover . Erosion is causing the stream
to bear argreater load of organic matter, and the leaching of
the exposed soil is causing the natural salt concentration
of stream waters to rise to a point Where it is deleterious
to fish life in the streams.
That these opinions may bear some weight, and that the
effect of beaver dams in producing acid conditions may be
benifical is suggested by Wells (14) in a study of the react-
ions of fishes to salts. Wells noted that fish became slug-
gish when kept in aerated neutral Water containing a small
amount of NaCl, whereas they became normal when a small amount
15.
of acid (HCl or CO2) was added to the Water. It was found
that fresh-water fishes can live in the presence of an acid
concentration, which would ordinarily kill them, if the
proper concentration of the right salts is present ; and
that concentrations of salt which would be otherwise intol-
lerable could be tolerated when the water was made to show
an acid condition.
An interesting fact was noted by Wells. He found that
fishes living under unfavorable conditions (in. Ol N. cacia) wº
showed sign of degeneration of the rays of the tail fin.
This degeneration continued until nothing but the blood–
reddened stub of the tail was left . The other fins were
not effected; the tail fin regenerated when the fish were
returned to favorable water. Day (2, p203.) States that in
a certain lake in the British Isles, there is a race of tail-
less trout which some author's claim can be traced as due to
the action of deleterious matter in the water. Day (loc. Cit. )
also quotes J. Harvie-Brown as saying, about 1876, "that a
contraction of the rays of the tail fins of the trout in the
River Carron occurred, and was believed due to the continuous/
%
*
polution of the water through the agency of paper mills",
Upon looking up the composition of the waste from paper mills,
(Griffin and Little '3 and Phelps '9) I find that among other
substances calcium is always present in large quanities, both
in chloride and other combinations. Therefore the phenomenon
reported by Day was likely due to the ore sence of an excess of
Calcium in the water.

Marsh (6) has shown that the waste of paper mill is
very toxic to fishes. However he believes the excess of
acidity or alkalinity is the chief causes for the toxic
effect, although there are other toxic substances.
16.
17.
Further Investigation Needed
Some of the reasons given for the necessity of removing
beaver dams need further investigation. In regard the bad
physical and chemical effects of be aver ponds to trout streams
much more investigation is needed. Cowles (1), in a study of
the hydrogen ion concentration of a creek, its water fall,
swamp and ponds has demonstrated that :
1. Various sections of the creek show decided differences
in pH values.
2. These differences are emphasized when the pH of sections
in which water is flowing actively is compared with the pH
of sections in which the water is flowing less actively, in
Other words, when the pH of rapids and waterfalls is com—
pared with the pH of pools and ponds.
3. In Ponds the pH is modified by the aquatic fauna and flora.
Aquatic vegetation reduces the CO content of the water and
causes a rise in pH value of the water. -
5. When water flows rapidly over a clean bed, most noticably
at falls and rapids, the pH is raised, probably as a result
Of aleration. r - -
These findings should be of help in constructing plans for
stream improvement , and in judging the relative merits of
certain stream improvement practices.
l.
18.
CONCLUSIONS
The improvement of trout streams necessitates that
each stream be treated as a separate biological unit.
Such generalizations that call for the removal of all
be aver dams cannot be made if stream conditions are
to be improved.
The warming effect of be aver ponds on the stream is
negligible to most trout streams.
Erosion caused by beaver dams is very prevelent in
Michigan streams, and a great amount of damage is
being done to trout streams as a result of beaver dams
in areas where the stream banks are of sand.
The hydrogen ion concentration of a trout stream is an
important factor in the trout environment, and further
investigations are necessary to determine how to regulate
the pH conditions of our trout streams to get better
trout production.
The health of the fish is closely correlated with the
pH condition of the stream. Waters which show a pH value
just on the acid side of neutrality are most favorable,
however, the fish can stand a much greater concentration
of H iOn S than OH ions.
The low pH values sometimes found in old beaver ponds
are probably not as detrimental to the trout as the pH
values indicate they would be ; the natural dissolved
salts in the water greatly reduce the toxic effect of
a high acid concentration.
19.
Recommendations
Each stream which is to be improved should be treated
separately as a distinct biological unit, with reference to
what it needs to bring it up to par as a fish producer.
First, a preliminary reconnaissance should be made of
the stream. (This can best be done by wading up the stream,
or if the Stream is too deep, by boat.) At this time make
notes of the conditions as you observe them, and also if a
good map is not on hand, make a map of the stream . .
Items to be observed are :
l. average depth, and width of stream
2. Character of bottom
Speed of current at various places,
The occurrence of rapids
gravel beds
Spring S in and along bank
small feeder streams and their charact a r
beaver dams, size, whether occupied
Sleuce dams or other oarriers in stream
Rubbish from logging operations, etc . ,
in stream
Amount of shading over stream
vegetation in stream
amount of cover for fish in Stream
eroded banks along stream.
number of deep places in stream, depth.
5. Describe the food cond it ions for trout.
Catch a few trout and determine their cond it ion by
the general conformation of their body. Examine their stomach
for food content. A formula which gives a comparative measure
of the food conditions with Which the fish have to contend with
has been used in England. Hewett (5) has found it of value here
in America, in telling whether a fish is prime , medium or in
poor condition. It is as follows:
Condition Factor = —weiºt in. 18.5. X 100,000
(length):
20.
The condition factor of a trout in normal condition should
be 4.2. Each number above or below this means a variation
of two and one-half percent from normal. The higher the
factor, the better the conditioni of the fish.
Having gathered this information, a plan for the improve—
ment of each stream can be made , which should be put into the
hands of the foreman in charge of the stream improvement crew.
21.
(l)
References Cited
Cowles, Rheinhart P. - The Hydrogen Ion Concentration of
f A Creek, its water-fall, Swamp and Ponds.
J/ FCology Vol. IV. 1923, p. 402
Day, Francis, 1887- British and Irish Salmonidae,
Williams & Norgate, l 4 Henrietta, St.
Convent Garden, London.
Griffen, R.B. and Little, A.D.- 1894, The Chemistry of Paper
making, Howard Lockwood & CO. N. Y.
Henderson, Lawrence J. - The Fitness of the Environment,
Macmillian Co . New York
Hewitt, Edward R. Better Trout Streams , p. 133.
Scribner & Sons, N. Y.
Marsh, M. C. 1907, The effect of some Industrial wrast es on
Fishes, House Documents. Vol. 64. Water Supply
and Irrigation papers, lº 06-07, p. 337.
Osterhout, W. J. W. - The Effect of Alkali on Permeability.
Journal Biological Chemistry. Vol. 19, p. 335.
{{ - The Effect of Acid on Permeability,
J. Biol. Chemistry. Vol. 19,
p. 443.
Phelps, E. B. - 1909, The Polution of streams by Sulphite pulp
U. S. Geo. Sur.
wastes. A study of possible reme dies,
Water Supply Paper 226.
Sei friz, William - Protoplasm - Mc Graw& Hill, p. 332.
Wells, . Morris Miller, The resistance of Fishes to different
concent rations and combinations of Carbon Ti oxide
and Oxygen. Biol. Bul. Wol. 25, No.
6
- The Reactions and Resistance of Fish as to Temperature
Transactions. Ill. Academy of Science,
**
Vol.
VII.
- The Relations of Fishes to Ions in their Natural
XXIX. No. 4 1915.
Frnvironment. Biol. Bullet in . Vol.
- The Reactions and Resist an c e of Fishes in their
Natural Environment to Salt. s.
Jour. Experimental Zoology. Vol.
19
3.
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