210 U. S. BUREAU OF FISHERIES.' 



The hatched fish easily sHp through the oblong mesh in the bottom 

 of the trays into the space below. They should be assisted in doing 

 this by gently raising and lowering the traj'^ at intervals, care being 

 taken not to raise them out of the water. 



After they are all hatched out and in the bottom of the troughs, 

 about the only danger to guard against is that of suffocation. They 

 frequently crowd together in heaps and dig down under one another 

 until some of them die for Avant of running water, which is less than 

 an inch away from them. The best remedy is to thin them out. 



John Pease Babcock, Assistant to the Commissioner of Fisheries 

 of the Province of British Columbia, in 1910 advanced a novel sug- 

 gestion that freshly fertilized eggs buried immediately under sand and 

 gravel would produce strong healthy fry at less cost than under exist- 

 ing hatching methods, and that fry so produced are stronger and 

 more capable of resisting the attacks of their active enemies. The 

 interestmg account of his experiments is reproduced entire:'^ 



In writing of the propagation of salmon and trout, some authorities state that con- 

 siderable loss is occasioned in natural propagation by many of the eggs becoming 

 embedded in sand and gravel; that all the eggs so embedded are lost. 



Observation and experiment in the propagation of Pacific salmon and trout for a 

 considerable period lead me to advance the theory that in natural propagation only 

 those eggs which become embedded beneath several inches of sand and gravel pro- 

 duce alevins which live to attain the fry stage; and that those eggs which are not 

 covered by several inches of sand and gravel are either consumed by active aquatic 

 enemies or destroyed by vegetable molds, commonly termed "fungus." 



My experiments have demonstrated that the burial of freshly fertilized eggs of the 

 nerka and other Pacific salmon does not smother them; that eggs so treated not only 

 live but hatch : and that if they are covered to a sufficient depth the alevins produced 

 survive and possess the instinct and power to work their way gradually to the surface; 

 that if buried beneath 5 or 6 inches of aand and gravel such eggs will hatch, and the 

 young ■will work their way up through the sand and gravel to the surface, and that by 

 the time thej^ emerge, have absorbed their sacs and are then exempt from the attacks 

 of vegetable molds. 



Eggs buried under 1 or 2 inches of sand and gravel produce alevins that work their 

 way up to the surface before the sac is absorbed, and upon reacliing the surface are 

 subject to attack by vegetable molds, and a very large percentage are thus destroj^ed, 

 as well as by the more developed forms of aquatic life. 



Eggs buried to a depth of 3 inches produce alevins that work their way to the surface 

 80 gradually that by the time they reach the surface their sacs are so nearly absorbed 

 that many, but not all, resist the effects of fungus. Alevins from eggs buried beneath 

 less than 4 inches of sand are liable to reach the surface while the sac is so thinly 

 covered that few, if any, survive the effects of fungous growth. 



The spawning beds of Pacific coast streams from California to Alaska (to which my 

 obser\ation8 have been confined), where the salmon spawn in numbers are, during 

 and after the spawning period, covered with more or less vegetable molds. Those 

 molds are particularly common in the beds of streams where great numbers of salmon 

 have spawned and died. Every experienced fish culturist knows that most waters 

 carry great numbers of spores of fungi, and how difiicult it is to prevent eggs and 

 aleAons from being attacked and injured by their growth. I believe that in natural 

 propagation fungous growths destroy more salmon eggs and alevins than all other 

 causes combined. The vegetable molds of Pacific streams are not active beneath 

 the surface of the beds of streams. Salmon eggs cast therein, if even thinly covered 

 with sand, are not injured by them. These molds do not affect the fry that have 

 nearly or entirely absorbed their aacs, but they are deadly if permitted to attach 

 themselves to either the eggs or the alevins. 



" Somo Experiments in the Burial of Salmon Eggs — Suggesting a New Method of Hatching Salmon and 

 Trout. By John Pease Babcock. Transactions, American Fisheries Society, HHO, pp. 39.3-395. Wash- 

 ington, 1911. 



This method has been carried out on a considerable scale by A. Robertson, a Dominion of Canada 

 hatcherv superintendent located on the Fraser River, and the results published in "Uatching Salmoq 

 Fr7 in Gravel," Pacific Fisherman, Seattle, Wash., Vol. 17, No. 6, June, 1919, p. 38, illus. 



