02 



BULLETIN OF THE BUREAU OF FISHERIES. 



channel as far out toward the end of the jetty as the fishermen go (in, 112); second, 

 from the main channel south ot Sand Island (113, 114, 115, 116); third, from the north 

 channel leading out of Bakers Bay at a point near Fort Canby (118); and fourth, from 

 Bakers Bay at the Whitcomb trap (117). 



The two chief types of muscle described, the pink muscle and the dark muscle, 

 were the only ones selected for analyses. The samples were taken in the mid-lateral 

 region just in the plane that cuts the front of the dorsal fin, the same region from which 

 histological samples came. 



The greater amount of fat in the lateral dark muscle as compared with the pink 

 was revealed by the microscope. But this fact is even more strikingly shown by the 

 quantitative percentages given in the table below. A glance shows that the percentage 

 of fat in the dark muscle is roughly twice as great as in the pink. There is no law to be 

 deduced about it from so few samples. The fattest salmon have relatively the highest 

 quantity in the pink muscle. The intermediate salmon from this station have a greater 

 reduction in the fat of the pink than in the dark. 



Particular attention is directed to the two females, no. 112 and 117. The 

 former is from the channel of the Columbia from the farthest point out toward sea. 

 The latter is from Bakers Bay, quite out of the main channel of the river. Undoubtedly 

 the great difference is due to the fact that no. 112 was just coming in from the sea. 

 No. 117 had undoubtedly lost most of its fat and is quite comparable with the salmon 

 in better condition from the spawning grounds of the Clackamas River at Cazadero. 



T.\BLE I. — AXALYTIC.\L DeTERMIN'.^TIOXS OF FaT IN THE TISSUES OP CeRTAI.N SaLMON 



191 1 Series. 



OF THE 



Significance of the jaf in Ilwaco salmon with reference to the normal quantity of fat at 

 the beginning of the migration. — In discussing the normal salmon type, the type at the 

 beginning of the migration deduced from the study of feeding salmon secured at Monterey 

 Bay, it was suggested that one might arrive at a better conception of the normal type by 

 figuring back from the first migration station. But Ilwaco fish show a number of signs of 

 physiological change presumably due to the cessation of feeding. Among these changes 

 the most striking are to be had by the examination of the alimentary tract, where, in 

 the stomach, and especially in the intestine and cseca, one finds extensive evidences of 



