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Puget Sound Marine Sta. Pub. 



Vol. 1, No. 11 



as the smallest from the dark, while the largest from the light was nearly 

 nineteen times as heavy as the smallest from the light. 



Table 16. Comparison of weights of largest and smallest fish from each 



group taken Sept. 17 



Record of Mortality 



A record of the mortality was kept from the time of hatching, on 

 November 15, to the end of March. During this period 263 dead were 

 removed from the darkened trough and 293 from the trough kept in the 

 light. Since there were approximately 4,520 fish in the dark trough and 

 3,800 in the light, there was therefore a mortality of 5.82 per cent among 

 the fish kept in the dark and 7.71 per cent among those kept in the light. 



Another point of practical importance is that it required much less 

 work to keep the dark troughs clean than it did those exposed to the light. 

 This was due to the fact that the light favored the growth of the low* 

 plant organisms. 



Observations on Humpback Salmon 



A study of the comparative development of the young of the hump- 

 back salmon (Oncorhynchus gorbuscha) was made under similar condi- 

 tions to those under which the young of the king salmon were studied. 

 This was done with a view to checking upon the latter. These eggs were 

 a part of a shipment made by the United States Bureau of Fisheries from 

 Afognak, Alaska, to a hatchery at Birdsview, Wash. About 2,000 of 

 these eggs were sent from Birdsview to the University of Washington by 

 parcel post, arriving November 24, 1914. Their temperature at the time 

 they were received was 17°C., which was gradually reduced to 12°C., and 

 then they were placed in the water of the troughs having a temperature 

 of 10.5°C. The eggs were later divided into groups, one of which was 

 placed in the dark trough and completely covered from the light, and 

 the other was placed in a white trough exposed to the light of day, in ad- 

 dition to which a 60-watt tungsten electric light in a cup-shaped reflector 

 was suspended within one foot of the surface of the water and kept 

 lighted continuously. 



The hatching period extended over a much longer period of time 

 than that required by the kings. This irregularity in hatching was largely 

 due to the low temperature of the water. It is also possible that the eggs 



