Effect of Light on the Development of Young Salmon 



E, Victor Smith, 

 University of Washington, Seattle. 



Introduction 



Fish-hatchery men in the course of theii work have made observa- 

 tions upon the influence of light on the young fish during the periods of 

 hatching and early growth, and are almost unanimous in their opinion 

 that the young fish thrive better in darkness than in light. They have 

 noticed a restless activity in the light that is not compatible with the best 

 and most rapid development. As a result the hatching troughs are painted 

 black and are kept in buildings in which the light may be regulated by 

 window shades. In recent years the hatchery superintendents, at least of 

 the west coast, have kept the eggs and alevins as much in the dark as pos- 

 sible. The fish are held in the hatching troughs until the yolk is absorbed, 

 after which those that are retained (and the majority are retained) are 

 turned into feeding ponds, a greater number of which are now kept under 

 cover so as to cut out all direct light. It was with the purpose of de- 

 termining more definitely the influence of light on the young fish that the 

 experiments recorded in this paper were undertaken. 



Equipment and Methods 



The work was begun at the Puget Sound Marine Station at Friday 

 Harbor, Washington, but the laboratory observations were carried on in 

 a small fish hatchery upon the campus of the University of Washington 

 during the season of 1911-1915. The fish troughs and baskets were of 

 the type commonly used in the hatcheries of the State of Washington and 

 each of the troughs held five baskets. The troughs were arranged as 

 shown in plate 17. 



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