HATCHING FRY IN GRAVEL. 



By A. Robertson, 

 Harrison Hot Springs, British Columbia. 



INTRODUCTION. 



In 1915 I was induced by the general decline in the salmon 

 canning industry and more especially by the scarcity of sockeye 

 salmon on the spawning grounds, and also by the doubtful success 

 of the present hatchery system, to make some investigations and 

 comparisons between it and the natural mode of incubation. 



Very little investigation sufficed to show that naturally hatched 

 fry were much superior in size and capability to the hatchery 

 product, and also that this superiority was attained in less time, 

 due to the prevalence of warmer water in the natural beds than 

 that used in the hatcheries. This superiority was apparent even 

 in the eggs; eggs dug up out of the gravel presented a florid and 

 swarthy appearance, which was lacking in our hatchery eggs, 

 and this indicated the presence of stronger embryos. When 

 the fry had absorbed the sac the difference was still more pro- 

 nounced, and particularly noticeable in the length of the gravel 

 hatched fry which were approximately twenty-five per cent longer 

 and fifty per cent heavier, and also in the size of the eye, which 

 was from one hundred to two hundred per cent larger. 



In strength and capability the difference was as between day 

 and night ; the wild natural fry hugged the shore singly or in very 

 small schools, and when pursued made for a hiding place with 

 frenzied erratic dashes. Hatchery fry when liberated swam aim- 

 lessly about, and only after repeated onslaughts of trout and ducks, 

 during which they lost heavily, were they herded into shallow water 

 and comparative safety. This condition of affairs is only to be 

 expected, for the smooth sides and bottoms of hatchery troughs 

 offer no inducement to the fry to seek hiding places, and their 

 instinct in this respect is soon dulled. On the other hand, fry 

 that have come from the gravel and darkness are movement and 

 light shy in the highest degree. 



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