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James G. (James George) Needham.

The life of inland waters; an elementary text book of fresh-water biology for students online

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This is manifest in many ways; among them, the
following:

1. There is lack of improved cultural varieties.
Our fishes are wild fishes. Save for a few races of gold
fishes all fancier's fishes and some not very desirable
varieties of carp, hardly any improvements have as
yet been made by selection and careful breeding.

2. There is lack of knowledge of the best kinds of
forage for fishes and of how it may be provided for their
use. This is half of the problem of raising any animal.

3. There is lack of any practical system of manage-
ment, that provides for the breeding and feeding and
rearing of stock, generation after generation, under
control.

In what, then, does the fish culture of the present
consist? Mainly in this one thing, the care of the
young. This includes the gathering and hatching of
fish eggs and the rearing of the young fishes thro their
earlier stages on artificial food in hatcheries. By this
means the enormous losses that occur under natural
conditions in early life are avoided, and vast numbers
of fry and fingerlings are grown to a size suitable for
planting in natural waters. Thus far the methods are
well worked out. Thus far our fish culture is bril-
liantly successful. But this is really only the first step.
How these little fishes when turned loose in pond and
stream shall find for themselves the means of a liveli-
hood is the unsolved part of the problem. Planted
here they seem to thrive; there, they fail. Every

*The substance of the following pages covering this subject was published
by the senior author in the Indianapolis News in 1909, and again in the Farmers
Magazine in 1912.



Fish Culture 385



planting in a new place is more or less an experiment.
Sheep culture would be in a state quite comparable
with the fish culture of to-day, if after rearing lambs
on the bottle they were turned loose in an unexplored
forest to shift for themselves.

The hatcheries are raising fry and not fishes. This is,
of course, what they were commissioned to do, the
underlying idea being merely that of putting back into
the lakes and streams a copious supply of young fishes
to occupy the place of the adult fishes taken out. But
experience has shown that the mere planting of fry
soon reaches its effective limit, after which the planting
of more fry is sheer waste. The conditions in the wild
are not such as yield much advantage from this intensive
propagation of the young. Oftentimes the fry planted
in the trout streams about Ithaca may be found shortly
afterward in the stomachs of the few adult trout that
live in the same streams. Feeding fishes on the young
of their own kind is not good husbandry.

The planting of fry and of fingerlings is effective
where conditions permit of their growth. The removal
of enemies is a supplemental measure of great value
where practicable. The care of natural feeding grounds
to prevent their destruction is very important, but
usually impossible, for want of enlightened public
opinion. Protecting of breeding fishes when on their
spawning grounds the time when they are most
easily discovered and destroyed is also very impor-
tant. And the bringing back into habitable places of
young fishes stranded in the side pools of bottomland
streams, where they would perish with the evaporation
of the water, is rescue work of a good sort. All these
things are done in the interests of public fishing at the
present day. They are such measures as are taken to
preserve wild game in a forest or livestock on an open
range. They have to do rather with hunting than with
husbandry.



386 Inland Water Culture

The day is coming is already at hand when he
who wants fishes fresh from the water will have to
raise them. Public waters are "fished-out." In spite
of closed seasons, and frequent plantings of hatchery-
reared fry, they continue to be "fished-out." With the
growth of our population they are going to be always
"fished-out ;" and there is no hope for the future of any
fishing that shall be worth while except in waters that
are privately controlled.

This does not mean that there will be no fishing in
the future. It only means that fish raising is going
the way wild pig raising has gone.

When game began to fail venison, wild turkeys, etc. ,
the pioneer began to raise pigs. At first he gave them
little attention, except at killing time, and furnished
them no food. He raised them about as we raise
fishes now. He turned them loose in the woods to
forage for themselves as we now plant fish fry in the
streams. They ranged the whole area where their
food grew.

Nowadays, thousands of hogs are raised where one
was raised then, but they do not run the range; they
are kept in small lots, and the broad areas are devoted
to raising forage for them. The present day method
of obtaining our meat supply is very unromantic as
compared with chasing a razorback hog with a shot-
gun through the woods at the end of the acorn season,
but it is the inevitable way of progress in animal hus-
bandry.

Raising animals and their forage together is not good
husbandry. It is exceedingly wasteful and unproduc-
tive; yet that is the way we still raise fish in America.
We ought to be doing better than this. It is idle to
plant more fish in the water until we can supply more
stuff for them to eat. And we cannot expect more
forage to grow unless we provide suitable conditions.



The Forage Problem 387

When we raise other stock-feed we find a few perfectly
definite things to be done:

1 . We clear a field and prepare it.

2. We fence it to keep out enemies and undesirable
competitors.

3. We plant it with selected seed; and after a
period of growth,

4. We use the crop at the time of its maximum
value.

All these things we shall have to do if we ever have
a real fish culture. The first two of these things are
usually cared for in the construction of fish-ponds ; the
other two are generally neglected.

The forage problem is less simple than is the raising
of pigs on clover, for at least two reasons:

1. Plant foods are not eaten directly by the more
valuable fishes, and often there are a number of turns-
over of the food stuffs before the fishes are reached.
For example, diatoms and other synthetic plancton
organisms are eaten by water-fleas and midge larvae,
that are in turn eaten by little fishes, that are eaten by
big fishes. There must be at least two turns-over
one kind each of plant and animal forage since the
desirable food-fishes are carnivorous.

2. There may be one or more changes of diet during
development. Thus the pike when newly hatched eats
such water-fleas as Simocephalus, (see fig. 92 on p. 186)
picking them one by one with automatic regularly-
timed snappings of its jaws. When grown a little
larger it eats midge larvae, mayfly nymphs and other
small insects. Still later, it eats large insects and
mixes small fishes in its diet; and as it attains full
stature it restricts its diet to frogs and larger fishes.
When grown it takes hardly anything smaller than a
golden shiner.



388 Inland Water Culture

Studies of the food of the common sunfish, Eupomotis
gibbosus,by the senior author ('08) have shown that in
Old Forge Pond, when one inch in length the food is
predominantly entomostraca and very small midge
larvae. When two inches in length, it is entomostraca
and midge larvae of larger size, together with small may-
fly nymphs (Caenis) and minute snails. When three
inches in length, it is grown midge larvae, mayfly nymphs
and caddis- worms. At this size apparently the diet of



FIG. 231. The common sunfish. Eupomotis gibbosus.
(Photo by George C. Embody)

entomostraca and small midge larvae is outgown, and
the fishes are seeking bigger game.

At three inches in length, this fish is itself the
favorite food of adult bullheads.

Excepting for a few fishes that range the open waters,
such as white-fish and lake herring, and that continue
to feed largely on plancton, there is at least one neces-
sary shift of diet accompanying growth; that from
plancton to the food of the adult. In an earlier chapter
(see p. 235) we have briefly indicated the principal
changes of diet then occurring.



Staple Foods



389



The food relations of aquatic organisms are exceed-
ingly complex. They change with age and season and
situation. The eater and the thing eaten often
exchange roles. Yet there are some fairly constant
food dependencies between the major groups of
organisms. These have been set forth by that veteran
student of the forage problem, Prof. S. A. Forbes, in the
table copied herewith (fig. 233), and this table indi-
cates (what detailed food studies at large abundantly
confirm) that fishes eat almost every living thing that
the water offers.




FIG. 232. The nymph of the dragonfly, Anax
junius, devouring a small sunfish.

The young of all fishes eat plancton. This sounds
like one point of general agreement, until we reflect
on the variety of organisms of which plancton is com-
posed. Which of these are best for use in fish culture
we scarcely know at all. Fortunately, they are of
nearly universal distribution in shoal fresh waters,
where the young of fishes are found.

Staple foods While a list of all foods, eaten by all
fishes would include practically every thing that is
found in the water, yet when careful food studies are
made there are a number of organisms so constantly
recurring that they stand out as of prime importance.
A few aquatic herbivores are found as commonly and



390



Inland Water Culture



as regularly in the stomachs of wild food fishes, as grass
would be found in the stomachs of wild cattle. And
just as stock feeding has made progress with the isola-
tion and study and increase of the grasses, so fish cul-
ture would be advanced by study and cultivation of
the staples of wild fish food.



PRINCIPAL

FOOD RELATIONS

or
AQUAT/C ORGANISMS
(ILLINOIS)


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HIGHER PLANTS \


PROTOZOA


fvyj Hoy


F.NTOA40STRACA \


WORMS \


I


IN sec TS J


MOLLUSKS


FISHES


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TURTLES


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BIRDS


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TERRESTRIAL WASTES


X


X


X


X


X


X


X


X


X


X


X


X










BACTERIA








X


X


X


X




X


X


X












ALGAC








X


X


X


X




x


X


X


X










HICHCR PLANTS
















X


X




X




X




X




PROTOZOA








x


X


X


X






X


X












/fOT/FCRS








X




X








x


x












ENTOMOSTRACA






X




X


x


X




x




X




X








WORMS
















X


x




X


X










CRAWF/SHFS














X








X


X




x


X




INSECTS






X










X


x




x


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X


X




MOLLUSKS














X


X






x




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FlSHt S












X


x


X


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FROGS






















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TURTLES














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JfRpenrs






























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FIG. 233. Forbes' (14) table of food (at left) and feeding
organisms (above).

Our best fishes are carnivores, and the animals they
eat are chiefly a few hardy, prolific, and widely dis-
tributed herbivores, such as water-fleas, scuds, midge
larvae, mayfly nymphs and other fishes. These feed,
of course, on plants; but we hardly know as yet what
plants are of most value to them. They thrive where
herbage abounds; and yet we know that abundance of



Water -Fleas



391



herbage may not necessarily mean good crops; for
weeds may be much more conspicuous in a pasture than
the close-cropped grasses that yield the forage there.
Certain species of pondweeds have been shown by
Miss Moore ('15) to be often used as green food, and
Birge ('96) has given many notes on the food preferences
of herbivorous plancton Crustacea.

The above mentioned staples invite much attention
but we shall have space for noticing but a few represen-
tatives of the groups to which they severally belong.



Digestive tract

\

Abdominal processes



Heart




Abdominal daws'



Posf- abdomen



If"



FIG. 234. Daphne (after Dodds).

Water- fleas As a typical representative of this great
group of herbivores, we may speak of Daphne (fig. 234).
Its manner of life and its enormous reproductive
capacity have already been briefly mentioned (pp. 186-7
and 306) . It is a very valuabb animal in water culture
on account of its ability to turn the great growths of
colonial diatoms and algae into excellent food for fishes.
Little is known, as yet, unfortunately, about the condi-
tions that make for its growth. Plancton studies of



392 Inland Water Culture

water-fleas have consisted in the main of the counting
of individuals in random catches; and, as Haeckel ('90)
long ago pointed out, this has about as much economic
value as the counting of straws would have in an oat
field.

The extraordinary growths of certain plancton algae
(Anabaena, Aphanizomenon, etc.) that often give
trouble in water-supply reservoirs, might be made into
fish food through the agency of daphnias, if we only
had learned how to manage our water crops.




FIG. 235. Gammarus fasciatus (after Paulmier).

Water-fleas are of very great value as food for young
fishes, they form also a considerable part of the food
of such larger fishes as are equipped with gill strainers
for gathering them out of the water. They are, of
course, largely absent from the water during the winter
season. Their value as forage organisms lies in their
good quality and their extraordinary reproductive
capacity.

The scuds This group of herbivores is typified by
Gammarus (fig. 235) a hardy, wide-ranging habitant of
the water weeds. It swims well, yet prefers to occupy
the sheltering crevices of dense leafage. It can leap



The Scuds 393



and dodge like a rabbit. It feeds on a great variety of
both living and dead herbage. It is itself a favorite
food for most fishes.*

The scuds are easily managed in pond culture. They
are not remarkably prolific. As already mentioned on
page 190, the possible progency of a single pair in one
year is somewhat less than 25,000. But they carry
their young in a pectoral brood pouch until well equipped
for life.

The chief merits of the scuds as forage organisms
(in addition to desirability as food) lie in their hardi-
ness, their ability to find a living and to take care of
their own young until well started in life, their constant
succession of overlapping broods thro the season and
their permanent residence in the water.

There are other herbivorous crustaceans of some-
what similar habits, among which the fresh- water
prawn, Palaemonetes, is probably useful as fish forage.

Midge larvce Larvae of midges of the genus Chirono-
mus popularly known as "blood-worms" (fig. 236) are





FIG. 236. A "blood-worm."

of prime importance as fish food. Small ones are eaten
almost as universally as are plancton entomostraca,
and the large ones continue to be eaten whenever
obtainable by fishes as large as adult trout and white-



*Its value has long been recognized by fishermen; on account of its abund-
ance in an excellent trout stream at Caledonia, N. Y., it has been locally known



as the "Caledonia shrimp."



394 Inland Water Culture

fish. In a most extensive examination of the contents
of fish stomachs Forbes ('88) found them "of remarkable
importance, making in fact nearly one- tenth of the
food of all the fishes studied/' Ferguson fed some red-
bellied minnows (Chrosomus erythrogaster) for 22 days
all the midge larvae (Chronomus viridicollis) they would
eat and nothing else. The grown minnows ate on an
average twenty-five blood-worms per day; the half-
grown ones, eleven. The senior author ('03) found that
25 brook trout taken at random from one of the best
natural ponds of the New York State Fish and Game
Commission at Saranac Inn, N. Y., had in their
stomachs more than 100 blood-worms each.

Midge larvae are among the most ubiquitous of
freshwater organisms. They feed mainly upon dia-
toms, and other simple organisms found in water or
growing sessile on or round about their homes; the
larger ones eat also the disintegrating tissues of the
higher plants. They dwell among all sorts of aquatic
plants, spreading their thin filmy tubes in every crevice
or along the stems. Little is seen of them there on
casual observation. They are like the rodents of the
fields, hidden in their runways. But one cannot place
a handful of any water weed in a dish of water without
soon seeing some dislodged midge larvae swimming
about the edges with characteristic figure-of- 8 -shaped
loopings of the body.

They dwell on the bottom (see fig. 134 on p. 226).
Indeed, as already noted, they may dwell far out on the
bottom under the deep water of great lakes. Here in
deep darkness and heavy pressure they dwell in enor-
mous numbers feeding upon the rich spoils of the plancton
rained down on them by gravity from above. They
often fill the soft bed with their silt-covered flocculent
tubes.



Midge Larvce 395



These tubes, like the ones on the stems, open to the
surface at both ends. The larva, within, holding on to
the silken lining of the walls with its claws, swings its
body in vigorous undulations, driving a current of
water thro the tube. This serves for respiration. It
also serves to drive diatoms and other food organisms
into net-like barriers spun across the exit; these bar-
riers are repaired or renewed after every catch. Food
is thus carried into the shelter of the case. But food
is also gathered from exposed surfaces whenever it can
be reached from open ends of the tube. It is gathered
by scraping the sessile diatoms and algae from stems.
For such work the mouth of the larva is equipped with
elaborate rakes and scrapers.

The larva of Chironomus is relatively simple. It
appears much less complex in organization than are
many of its insect competitors. It has a cylindric
worm-like pale and naked body with a bifid proleg
underneath at the front and a pair of prolegs behind,
caudal tufts of bristles, and a few simple gills. The
prolegs are armed with hooks and on them it creeps
somewhat like a looping caterpillar. From its mouth
it spins the fluid silk, and spreads it ere it hardens with
the front proleg. All in all, it is a shy and defenseless
and secretive creature, without any special gift of
locomotion.

This apparent weakling has been able to possess
itself of the entire littoral region of the earth, perhaps
by reason of the following characteristics :

1. Ability to live on foodstuffs that have a very
general distribution.

2. Ability to build its own shelter.

3. Consequent adaptability to variety of conditions.

4. Great reproductive capacity.

5. Brief life cycle.



396



Inland Water Culture



Chironomus lays several hundred eggs, and in the
warm, season a generation may completely develop in
five or six weeks; so the very considerable increase of
one brood may be rapidly repeated in geometric ratio.

The limitations to its use as a forage organism in fish
ponds lie in its complicated life history. It quits the
water at the end of the pupal stage. It flies away,
mates in the air, and returns to the water to lay its eggs.
During its aerial life it is not easily managed.

Mayfly nymphs constitute one of the most important
groups of aquatic herbivores. We single out Callibaetis
for illustration of another staple fish food. It is an
active nymph that swims from place to place by means




FIG. 237. The nymph of Callibaetis: Drawing by Anna H. Morgan.
(Prom Annals Bnt. Soc. America)



Callibcztis 397



of quick strokes of its tail and gills, and that clambers
freely about over shore vegetation. It is an artful
dodger; and it is protectively colored. It feeds on a
great variety of vegetable substances living and dead,
and hence finds abundant food in every weedy pond.
It is eaten by every carnivore in the pond that can
catch it ; and doubtless it has many enemies that exceed
it in swiftness and many others that lie in ambush and
capture it by stealth. Hence, tho nearly always
present, it rarely appears very abundantly in old
ponds.

The life cycle of Callibaetis is run in less than six
weeks. A single female may lay 1000 eggs. If all
these were to develop and reproduce, the increase from
a single pair during one summer season would be some-
thing like this:

ist brood 1,000 (half females)

2d brood 500,000.

3d brood 250,000,000.

4th brood 125,000,000,000.

These alluring possibilities of increase in an organism
that is choice fish food once led the senior author into a
series of experiments that extended through two years
and that met with uniform failure because the breeding
of the mayflies could not be controlled. The rearing
was easily managed but even with the largest measure
of freedom that could be provided, the adults would
not mate and lay eggs in captivity. The problem of
their successful artificial propagation is still unsolved.
However, there has never been a new pond opened at
the Cornell University Biological field station, that has
not received the eggs of wild females of Callibsetis, and
that has not raised a good crop of the nymphs ere
their slower-breeding carnivorous enemies developed.



398 Inland Water Culture

Mayflies, like Callibaetis and the little Caenis, that
have a number of broods each season with overlap of
generations, are suited for use in forage propagation
because at all times of the year nymphs of good size are
present in the water. On the other hand, such forms as
Blasturus cupidus, which flies in May, and Siphlonurus
alternatus which flies in June, are absent from the water
at the close of their breeding season or are represented
there only by eggs and very minute nymphs.

Best known of the mayflies that fishes eat are the
nymphs of the big burrowing Hexagenias from lake
and river beds. Food examinations have abundantly
shown their importance. However, they develop
slowly, requiring at least two years to reach maturity.

The Hexagenia nymphs are natural associates of
bloodworms on the lake bottom. They, and the blood-
worms with them, and the entomostraca swimming
above them are the mainstay and dependence of the
lake's fish population.

Other herbivorous insects of promise as forage organ-
isms are caddis- worms and aquatic caterpillars. Other
invertebrates are a number of pond snails. But the
animals above discussed we regard as most important.

Forage fishes The largest single item in the bill-of-
fare of fishes generally is other smaller fishes. Herbi-




FIG. 238. The golden shiner.

(Photo by George C. Embody)



The Way of Economic Progress 399

vorous fishes, non-competitors for food, may therefore
be used to furnish a principal crop of animal forage.
For this use carp are objectionable because they grow
too fast and soon become too large to be swallowed by
the other fishes. They eat the eggs of bass, and root
up the bottom and tend to exterminate their own
vegetable forage. Minnows are also objectionable
because they eat the eggs of other fishes. But very
valuable for such use are the golden shiner (fig. 238),
and the gizzard shad, (Dorosoma cepedianum), of our
great rivers. Even the goldfish is an excellent agent
for turning masses of blanket algae and other soft fresh
vegetable foods into excellent forage for larger fishes.

The way of economic progress The future of fish
culture lies in further scientific studies to be made
along the lines that have proven of value in the
raising of land animals. More knowledge is what is
needed :

1. Intimate detailed knowledge of the fishes them-
selves is needed; knowledge of their natural history,
their requirements of food and of protection for
their young; their enemies, internal and external;
their natural races and possibilities of improvement by
breeding. Only such knowledge can fernish a
basis for developing methods of control.

2. Equally detailed knowledge is needed of the
economic species that furnish forage or that menace
the welfare of the cultivated species; knowledge of all
the more important ones, from the forage fishes, crusta-
ceans, insects, snails, etc., even down to the diatoms.
The product must be followed to its principal sources
and the cultural relations that all these organisms bear
to each other must be better understood. The enemies
of every stage of fish life must be studied (fig. 239).



400



Inland Water Culture




3. More knowledge
is needed of the water
bodies themselves;
knowledge of their


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Online LibraryJames G. (James George) NeedhamThe life of inland waters; an elementary text book of fresh-water biology for students → online text (page 22 of 26)