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CAUSES OF DEGENERATION OF AMERICAN TROUTS IN AUSTRIA

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By Johann Franke

Director of the Fish-Culture Establishment at Studenec and Secretary of the
Fishery Committee for the District of Krain

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Paper presented before the Fourth International Fishery Congress
held at Washington, Wis: Ke September 22 to 26, 1908

BULLETIN OF THE BUREAU OF FISHERIES : : : : : : VOL. XXVIII, P. 983-989
Document'No:699' 2 £ 9 $ 2 PoP PoP ge fo 2 gop ror fo © sued) Apnl, 1910

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CAUSES OF DEGENERATION OF AMERICAN TROUTS IN AUSTRIA.
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By JOHANN FRANKE,
Director of the Fish-Culture Establishment at Studenec and Secretary of the Fishery Commission for the
Province of Krain.
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[Translated from the German.]

I have had to do with the feeding of rainbow and brook trout in ponds and
inclosures for seventeen years. I have. had experience with rainbow trout in
clear running water for thirteen years, and much more thoroughly and in detail
with brook trout for eight years.

The two species are excellent as breeders, first class and far superior to the
native trout (Salmo fario). They can consume an astonishing amount of food,
their appetite is extraordinarily persistent, and they repay the voracious feeding
by astoundingly rapid growth; they remain well, keep their beautiful vivid
coloring, and yield excellent spawn, even ‘‘red eggs”’ when in the proper condi-
tion and in surroundings suitable to salmonoids. The view that the degenera-
tion of this fish, wherever it has occurred, is a result of natural tendencies and
the qualities of our water, and that the degeneration was to be expected in the
nature of things, I entirely repudiate, for I am convinced that the degeneration
is the effect of artificial conditions unsuitable to salmonoids.

The true reason for the degeneration of these fishes is in faulty methods on the
part of the fish culturists. The brook trout especially has been greatly dis-
credited in Vienna and in other places, being pronounced very weak, its flesh
distasteful, etc. This may have been true, as it is being bred in a most irrespon-
sible way, the fish being given all kinds of impossible food in order to produce it
quickly and cheaply. There is great competition in the sale of spawn, small
producers selling not directly to the users but to agents who advertise not only
hundreds of thousands but even a million or two as being their own product.
The producer does not obtain even 3 crowns (60 cents) per thousand in many
cases. Much of this has already been published in German special papers

985

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986 BULLETIN OF THE BUREAU OF FISHERIES.

discussing the subject of degeneration, and many astonishing facts have been
brought out. Good eggs are cheap even at 5 crowns (or $1), and a breeding
establishment can be maintained properly and on a businesslike footing only
when the eggs bring 10 crowns. At present the fishes are bred down into a
wretched condition. The much desired eggs from America will degenerate in
the same way if the method of breeding for reproduction is not henceforth differ-
ent from that which has prevailed.

The unfavorable conditions surrounding the American trouts in this country,
brought to my knowledge through experience during the long period I have men-
tioned, I have found to be due partly to inadequate insight into many essentials
of fish culture, and partly also to things which could not be changed. I have
been able, however, to acquaint myself with some of the phenomena of degenera-
tion and their causes, and some of them I have successfully combated.

I consider the principal causes of degeneration to be:

1. Unhealthy pond bottom, i. e., bottom on which ooze and remnants of food
as well as excretions accumulate for months at a time. The slower the current
and the longer required for the water to run off, the more dangerous grow the
conditions even at a low temperature of from 10° to 13° centigrade. The planting
of water cress on the bottom and the introduction of carps and perches is not suffi-
cient by any means, as these fish do not wallow in the ooze at temperatures of 10° to
13°. . For example: A spring pond having an area of 140 square meters and a
depth of from 60 to 100 centimeters was stocked about the end of August with
1,500 rainbow trout of the same year, and disease appeared in January, 1897;
it was impossible to drain the basin without lowering the level of the water in
the principal pond and disturbing the entire establishment. The ooze was
taken out by means of a strong pump and a rubber hose; in some places it was
black and bad smelling. The disease disappeared entirely a few days later.
After this I succeeded in saving the one-year-old fishes in low-water ponds with
weak currents by means of frequent pumping out of the ooze and by keeping the
bottom clean.

2. Substitutes for the natural food. Fresh flesh of fishes (I had only fresh-
water fishes) must be considered as natural by the effect produced, even if it is
cooked. I never succeeded in keeping the trout healthy for a long period when
using substitutes (a mixture of fresh blood cooked with shrimp meal, or the
spawn of sea fishes, or fish meal—Ideal brand—and flour as a binding material)
without an abundant addition of fresh fish. Within two and at the latest within
three months there were traces of change of color to a darker, dimmer hue with a
bluish tinge, more noticeable in the many-colored brook than in the darker rain-
bow trout. If they reached the blackish-hue stage they could not be saved. In
such cases live natural food without any adulteration proved the best of remedies.

DEGENERATION OF AMERICAN TROUTS IN AUSTRIA. 987

Latest example from the current year: Spring pond of 90 square meters, good
depth, and slow current of the water at a temperature of 10° C.; there were in the
middle of February 400 beautiful rainbows from a lot of the previous year, of
which 950 had been taken out in apprehension of lack of water in winter and
sent to other places in November. The suspicious looking bluish tinge was
already awakening our anxiety; there was danger in delay, but the best remedy
was natural food. A broad flat pool with spring water flowing through it, all
covered with vegetation and algz, had become free of ice. Here were caught by
means of a fine dip net a mass of various small animal life, small and large larvae
of mosquitoes, crawfish, woodlice, small fishes, and even bullheads. The small
animal forms came slowly to the surface from the thick forest of vegetation and
dirt and were caught up. The entire mixture was then taken to the shallow
water near the bank of the pond, where the trout themselves took the food out
of this mixture. The pool supplied ample food year after year, thus saving the
fishes more than once, though diminishing in abundance each year toward the
month of May. Seven of these rainbows died, but all the remaining seemed
well and acquired within three months their normal aspect, which they kept.
To be sure, they were given no more food substitutes. The last 75 fishes were
sent away in July; they weighed each 13 kilograms and stood very well the
transportation of 614 hours, as did also those which were sent away earlier.

As long as the materials for the diet of the small fry and young fishes con-
tained crustaceans and fresh fish, the breeding and rearing went on exceedingly
well, but in winter, with the forced use of substitutes, or in proportion to the
lack of fresh fishes, the trouble began.

3. Insufficient flow of water through the ponds. The two large ponds have
an old accumulation of ooze at the bottom some 20 to 100 centimeters deep;
can be emptied only down to five-sixths of their contents at best, as the entire
system of springs of the establishment flows through these. This, which it is im-
possible to correct, is surely an evil, but it had no apparent bad effect upon
the larger salmonoids and the breeding fishes so long as the flow was abundant.
When the supply grew less, in 1897-98, there appeared again the exophthalmia
and the ‘‘staggers’’ now and then. With the decrease of springs these phe-
nomena grew more frequent, several of the native trout (jario) became miser-
ably thin, and several rainbow trout yielded spawn that could not be used. In
1904 the establishment went through two or three months without the flow of
the springs, and in summer the surface water of the principal ponds at a certain
distance from the inflow of the water had a temperature of 18° and near the
exit a temperature of 21.2°C. At that time the water was calm, for what cur-
rent could be expected from a couple of second liters in an area of 134 hectares?
The water near the bottom was cooler by some 2° to 4°, and the trout lay there

988 BULLETIN OF THE BUREAU OF FISHERIES.

in lethargy and without appetite; only the roaches and a few carp swam
slowly about. Good spawn was obtained only in ponds where there was an
outflow of springs; there were but few brood fish in the places where formerly
could be found some 100 kilograms; and good roe fishes were in still smaller
number. In addition to this symptom of degeneration there were others in
an increased degree. Anzmia, however, did not appear in the rainbow or brook
trout.

No food substitute whatever was given to the fish in the principal pond, in
order to forestall a beginning of degeneration. This, however, was without
avail. The regulation of the course of the principal river of the country gradu-
ally drained away the living water supply of the establishment; the springs
coming from the great subterranean stream of the Laibach field went dry, and
we were forced to abandon the locality in July of this year.

It is impossible to demonstrate in a more striking way than this the neces-
sity of a good flow of water, one of the three conditions—infected bottom of
ponds, continuous use of substitute foods, and insufficient flow of water—which
brings about phenomena of degeneration, the more rapidly and in so much the
higher degree if two or all three causes are operating at the same time.

And what about native trout? I would ask only when and where has there
been observed in this fish any greater power of resistance against the above-
mentioned causes of degeneration? It is not less sensitive than the brook trout
and considerably more so than the rainbow.

As to the American trouts in running streams I know of only one drawback
to the rainbow, namely, that there is no reason to suppose that it will remain
and make a constant abode in particular waters, or that it will immediately
leave the abode of its youth; water seemingly of the same character was in
reality quite different. In two cases the fry developed in four years into mature
fishes. The lingering of the rainbow in certain waters has astonished us as
often as its disappearance from the same localities.

The brook trout shows more tendency to remain. In waters where food is
abundant this fish surpasses even the rainbow in rapid growth. Contrary to
the general opinion that it must have cool water, I saw this fish thrive one
summer in water having a temperature of 18° to 20°C. In small creeks, poor
in food, it scarcely thrives as well as the native farto. In the Stara Voda, which
stream I had under my control from 1901 to 1908, it grew to be the principal
fish after the first introduction as small fry, while only a few of the rainbow
trout had remained there. The native farto, which was already there and did
well, remained far behind the fontinalis in numbers and in rapidity of growth.
Only during the last two years, when the stream suffered, like the establishment

DEGENERATION OF AMERICAN TROUTS IN AUSTRIA. 989

of Studenec, from lack of water and of current, the farzo stood it better than
the fontinalis and appeared in greater numbers than the latter.

Up to the time when I began to control this stream I knew nothing about
the possibilities of the brook trout. Introduced into the stream in March, rgo1,
as small fry which had not yet been fed, several fishes were caught by me in
August weighing from 0.3 to 0.5 kilogram, while the largest weighed 0.65 kilo-
gram; they were fat and round, beautifully tinted, and their flesh was exquisite.
The spawn (spawning season from November 7 to December 15) proved good
in the hatchery, although the eggs were smaller than those of older fishes.
Three-year-old fishes weighed 0.75 kilogram. I never dared to let them grow
older through fear of their being stolen.

My regret over the drainage of this stream is greater than for the ruin of
the fish-culture establishment.

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MN 859 a I

LIBRARY OF CONGRESS

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