106 Puget Sound Marine Sta. Pub. Vol. 1, No. 11 



As much water as possible was removed by wiping the under side of the 

 wire gauze strainer in which they were caught. The results of this weigh- 

 ing are given in table 18. These figures show that the average weight of 

 those kept in the dark was 9.97 per cent greater than those in the light. 



Table 18. The weight of humpback salmon from darkeness and light at 

 time of closure of yolk-slit 



After the yolk was absorbed the young humpbacks developed in a 

 very irregular way. Many of them made almost no growth while others 

 m.ade very rapid growth, far exceeding that of the kings of the same age. 

 By June the large ones began to eat the small ones. The mortality up to 

 this time was very high both in the dark and in the light. The results 

 were such that it seemed scarcely worth while to make further observa- 

 tions to determine the influence of darkness or light upon them. 



Up to the time of complete yolk absorption the dark and light envir- 

 onment produced similar effects upon the humpbacks to those observed in 

 the kings. They hatched more quickly in the light than in the dark, at least 

 during the earlier part of the period ; those in the light were decidedly 

 more active than those in the dark; and at the time of complete yolk ab- 

 sorption those in the dark were considerably heavier than those in the 

 light. The experiment on both king and humpback salmon is being re- 

 peated this year and up to the present time, December 28, 1915, the re- 

 sults confirm those recorded in this paper. 



SUMMARY 



1. During the hatching period of young king salmon those kept in 

 the light exhibited a restless activity not seen in those kept in the dark, 

 as a result the former hatch out more quickly than the latter. 



2. After the fish were hatched, those in the light continued to ex- 

 hibit a restlessness and activity not shown by those kept in the dark. 

 Those in the light left the bottom of the trough and distributed themselves 

 throughout the water much sooner than those retained in the dark. This 

 activity on the part of those in the light caused them to absorb the yolk 

 more quickly than did those in the dark, and at the same time the in- 

 creased metabolism due to this increased activity resulted in a retardation 

 of their growth, so that at the time of complete yolk absorption, the in- 



