210 U. S. BUREAU OF FISHERIES. 
The hatched fish easily slip 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 tray 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 want 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 
interesting account of his experiments is reproduced entire :4 
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 sand 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 they 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 reaching the surface are 
subject to attack by vegetable molds, and a very large percentage are thus destroyed, 
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 
so 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. 
observations have been confined), where the salmon spawn in numbers are, during 
and after the spawning period, covered with more or less vegetable molds. These 
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 difficult it is to prevent eggs and 
alevins 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 sacs, but they are deadly if permitted to attach 
themselves to either the eggs or the alevins. 
a Some Experiments in the Burial of Salmon Eggs—Suggesting a New Method of Hatching Salmon and 
Trout. By John Pease Babcock. Transactions, AMerican Fisheries Society, 1910, pp. 393-395. Wash- 
ington, 1911. 
This method has been carried out on a considerable scale by A. Robertson, a Dominion of Canada 
hatchery superintendent located on the Fraser River, and the results published in ‘‘Hatching Salmon 
Fry in Gravel,’ Pacific Fisherman, Seattle, Wash., Vol. 17, No. 6, June, 1919, p. 38, illus. 
