NOTES ON FISH-CULTURE IN GERMANY. 
323 
As regards the care of fish water, great stress was laid on the proper pains in 
establishing and maintaining the spawning- places. In Prussia certain spawning-places 
were protected all the year around in all larger sheets of water. The speaker did not 
consider it useful to place entire bays and coasts under protection, as these places 
then become favorite places of sojourn for predaceous fish. Arrangements should be 
made not to place in ponds too many kinds of fish living on the same kind of food, 
but father such as live on different kinds of food. In this respect special regard 
should be had to shoal-water fish and to deep-water fish. Pish waters cared for in 
this manner have yielded good results in Bavaria. 
As regards the pilce the speaker stated that it was one of the most unsatisfactory 
fish for raising, on account of its voracity. Experiments had shown that it took 47 
pounds of meat to raise 1 pound of pike. A beginning, however, had recently been 
made to raise pike in special ponds having a good supply of small fish. This had, for 
instance, been done in ponds having too large a stock of carp. 
In regard to artificial impregnation , the speaker stated that, since the so-called 
“dry method” had been adopted, the percentage of impregnated eggs had increased 
from 50 to 80 or 00 per cent. Numerous investigations had shown that the spermatozoa 
of the male fish do not live in the water longer than 22 seconds, during which short 
time the eggs are not nearly all impregnated. Immediately after impregnation the 
eggs are very tender to the touch; and the fact had been positively ascertained that 
if a few days after impregnation the roe is disturbed on the frames in the apparatus, 
many eggs will perish. The germ in the egg is specifically lighter than the fluid 
contained in the shell, for which reason the germ always rises to the top. If the egg 
is turned, the germ again rises to the top, and this causes such a disturbance as to 
make the impregnated egg die. This does not apply, however, to gwiniad, perch, and 
some other kinds of fish, whose roe develops best if it is well stirred in apparatus 
specially constructed for the purpose. 
The speaker finally showed, greatly magnified, the principal small aquatic ani- 
mals which serve as food for fish. Experience had shown that Daphnia — very small 
crustaceans, most of them measuring no more than 1 to 2 millimeters in length (0.04 
to 0.08 inch) — if properly treated, can be brought to a great degree of productiveness. 
The method is very simple. A ditch or small pond is filled with dry leaves, suitable 
aquatic plants, and manure (opinions differ as to the kind of manure to be used); a 
number of Daphnia are planted there and under the influence of the summer heat 
develop very rapidly. If the water in the ditch is allowed to flow through a pipe into 
the pond where the young trout are kept, the fish will thus be supplied with a sufficient 
quantity of natural food. When the fish are larger they are fed on larva* of flies raised 
in Le Petit’s apparatus. As the larvae often grow too large for the fish, this difficulty 
is obviated by placing a fine grating before the opening of the apparatus so that only 
smaller kinds of flies can enter and lay their eggs; whereby, of course, smaller larvae 
are obtained. As the air becomes cooler toward autumn the young flsh are fed on the 
roe of salt-water fish (especially cod roe), which can be bought very cheap. When- 
ever the temperature is higher, the roe should be slightly salted and afterwards well 
soaked before it is fed to the fish by meaus of the feeding- wheel. 
After the flsh have grown they are distributed in small ponds measuring 15 to 20 
square meters (101.5 to 215.3 square feet), which are always kept supplied with 
aquatic plants producing fish-food. The trout are now fed on a mixture of 30 per 
