316 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
retain their fertility. It was shown beyond question that both may be held at least 
48 hours, and. practically as great a percentage of impregnation procured as if applied 
immediately after they are taken from the fish. 
I will quote from the records of the station the results of a few experiments which 
will fairly illustrate the whole. One lot of eggs taken on December 6 was impreg- 
nated on December 7 with milt taken on December 4; percentage of impregnation, 98. 
A lot taken on the same day and impregnated immediately with milt just taken showed 
the same percentage of impregnation — a mere coincidence so far as exactness is con- 
cerned. Another lot, where the spawn and milt were both taken on December 6 and 
impregnated on the 7th, showed 97 per cent impregnated. Still another lot taken on 
the 7th and immediately impregnated with milt taken on the 4th showed 95 per cent 
impregnation. Fourteen tests were made, and it may be inferred from them that 
neither the eggs nor milt can be carried past the third day with good results. With 
all those carried past that time the percentage of impregnation ran from 0 up to 6. 
In this work care was taken that the eggs and milt should be kept entirely free 
from water and other foreign substances. The eggs were held in pans and the milt in 
corked vials, both being kept in running water at the then prevailing temperature ot 
the lake — about 35° F. One lot of milt, where a very small clot of excrement had 
entered the vial, was used as an experiment 48 hours after it was taken and failed to 
impregnate any eggs. 
One of the important problems in whitefish-culture in Lake Erie has been the 
successful penning of adult fish in order to hold them until their eggs are sufficiently 
developed or ripe. Up to the past season this has been a failure so far as practical 
results are concerned, for the reasons that the pound nets are so scattered and so few 
fish are taken from each on each day that under the usual methods sufficient fish 
could not be procured, and that when penned in stationary inclosures in landlocked 
bays — the only place where the crates can be held during stormy weather — the water, 
during specially warm periods, gets so warm as to render the fishes unhealthy and 
the eggs become congested, or what is called “ caked,” in the abdomens of the females. 
Both these causes have been removed at Put in Bay station the past season. 
A supplemental net 3 feet in diameter and 7 feet long, held open at the top and 
bottom by iron rings, is placed at each pound net by fastening one side to the down- 
haul stake and the opposite to the rim line of the pot, thus holding the top about 3 feet 
above the surface of the water. When the pound is lifted all the whitefish are singled 
out and lifted by a net made of coarse, open cloth — an ordinary net is too harsh on the 
fish and injures their delicate scales and fins — and dropped into the supplemental net, 
from which they are taken and placed in special tanks on the deck of the station 
steamer and removed to the crates located near the station. It will be readily under- 
stood that by this means the fish can be procured from a large number of nets, while 
otherwise only such can be saved as are procured by one lifting boat, accompanied by 
the steamer, as all the boats in a given locality lift at about the same time, generally 
early in the morning. After the fish are in the supplemental nets they can be col- 
lected by the steamer at leisure, taking all day for it if necessary. 
To avoid the danger of too warm water the pens or crates are secured between 
long pine-boom logs, the whole making a substantial raft, which can be towed outside 
and anchored where good currents and safe temperature can be procured until danger 
is past. The crates are surrounded on all sides by walks for convenience in sorting 
and handling fish. The compartments of the crates are 8 feet square and 7 feet deep, 
