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 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 tish 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 dowii- 

 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 whiteiish 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 supplement ;il 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, 



