ARTIFICIAL. PROPAGATION OF WHITEFISH, ETC. 5 



through artificial propagation from 75 to 95 per cent are productive. 

 Practically all the eggs taken for hatching purposes are obtained 

 from fish caught by the commercial fishermen and otherwise would 

 be lost or sent to market with the fish. 



The methods of culture hereafter referred to are those pursued at 

 the Put in Bay (Ohio) station, but they do not differ in any essen- 

 tial particular from those in general use. In the fiscal year 1921 

 the Bureau of Fisheries hatched and planted 420,450,000 white- 

 fish fry. 



COLLECTION AND INCUBATION OF EGGS. 



The taking, impregnating, and handling of whitefish eggs are 

 simple processes, though they require great care at every stage. 

 Eggs are often injured by undue haste in stripping, and many are 

 lost by allowing them to fall too great a distance into the spawning 

 pan. The eggs are very delicate when first taken and before the 

 absorption of water has made the investing membrane tense, and if 

 roughly treated they will be seen to be ruptured as viewed under the 

 microscope. With care about four-fifths of the eggs will hatch. 

 While scarcity of milt may lead to nonfertilization of the eggs, the 

 manner in which the milt is brought in contact with the eggs is a 

 more common cause of failure. 



The eggs supplied by each spawn taker should be examined daily. 

 If it is found that a considerable number have ruptured yolks, it 

 may be taken for granted that the spawn taker has handled the fish 

 and eggs roughly, and if many are unimpregnated it is evident that 

 he did not use sufficient milt, or that it was not properly applied to 

 the eggs. Eggs or milt taken from fish that have been dead for any 

 length of time should not be used. 



At Put in Bay eggs are obtained from fish captured in pound nets 

 and gill nets, often at considerable distances from the station. The 

 spawn taker, who is employed to take the eggs from the fish as they 

 are lifted from the nets into the boat, has with him two or three 6- 

 quart pans, coated with asphaltum varnish to prevent rusting, in 

 which he takes the spawn, a wooden keg or tin can holding from 10 

 to 15 gallons, a lO-quart wooden pail, and a tin dipper. He is 

 clothed in waterproof garments, and his left hand is covered with a 

 woolen mitten for convenience in handling the fish. 



After several ripe females and some ripe males are collected a fe- 

 male is taken up and the body slime, which would interfere with 

 impregnation if allowed to fall into the pan, is carefully removed. 

 The spawn taker then grasps the fish firmly in his left hand just for- 

 ward of the tail. The right hand is placed under the fish just back 

 of the pectoral fins, and the fish is held firmly against the body, with 

 the vent 4 or 5 inches from the bottom of the pan. This position of 

 the fislfs body brings pressure on the abdomen, facilitates the flow 

 of the eggs tlirough gravity, and prevents them from being injured 

 by falling too far. 



On applying a gentle pressure the eggs will flow in a steady liquid 

 stream about a quarter of an inch in diameter, and a considerable 

 portion of them can be ejected before the hand need be moved. As 

 soon as the stream slackens the hand is moved slowly toward the 

 vent, but only sufficiently to keep the eggs flowing steadily. Wlien 

 the stream finally stops, the hand is placed in its former position 



