PROGRESS IN BIOLOGICAL INQUIRIES, 193 3 341 



means for |3r<)tection of migratory fish at the Columbia River Dam 

 at Bonneville, Oreg. 



KARLUK RED-SALMON INVESITGATION 



The biological investigation on the Karliik River red salmon, 

 conducted by J. T. Barnab_y, was continued during the past year. 

 The prime purpose of this investigation is the determination of the 

 ratio between the spawning escapement and the return from that 

 escapement; the determination of the fluctuations occurring in these 

 ratios from year to year; and the causes for such fluctuations. A 

 thorough knoAvledge of the magnitude of these fluctuations and their 

 causes will enable an economically sound regulation of this fishery 

 as well as of other fisheries of a similar nature. 



Another marking experiment was initiated, 40,000 seaward mi- 

 grants being marked by the amputation of the two ventral and the 

 adipose fins. The returns from this experiment will appear in the 

 riins of 1934, 1935, and 1936. The 1933 run was sampled throughout 

 the season for the purpose of recovering fish marked in ]:)revious 

 years; 178,080 fish were carefully examined and 931 marked fish 

 recovered. These marking experiments will, when completed, 

 enable the determination of the fluctuations in the ocean mortality 

 of these red salmon, the calculation of the number of seaward mi- 

 grants during the year each experiment was initiated, and the cal- 

 culation of the mortality rate during the time these fish spent in 

 Karluk Lake. 



Scale samples were taken throughout the season for the purpose of 

 determining the age composition of the run. A weir was again 

 operated in the Karluk River and the age composition of the escape- 

 ment can also be calculated from the data thus obtained. 



Special attention is being given the data collected to date in respect 

 to returns from known escapements to ascertain to what extent hered- 

 ity influences the time of migrating to the ocean and the time of 

 returning to spawn. There is a considerable degree of variation 

 •from year to year in the age composition of the runs and likewise of 

 the escapements. It is felt that this study, together with the limno- 

 logical investigations being carried on at Karluk Lake, will, at least 

 to some extent, clear up the problem of why escapements of similar 

 magnitudes produce different-sized returns. 



Two trips were made to Karluk Lake, one during July and one 

 during October, at which time spawning-ground surveys were made 

 and limnological data collected. 



In addition to the red-salmon run, the Karluk River supports a run 

 of pink salmon of considerable importance. With a normal escape- 

 ment, the ]nnk salmon occupy the spawning grounds in Karluk Rivei- 

 proper and none enter Karluk Lake to continue on to the red-salmon 

 spawning beds. Thus, while both species spawn in the same water- 

 shed, their spawning grounds are distinct. Occasionally, however, 

 due to a series of conditions unusually favorable to the pink-salmon 

 population, certain brood years produce extremely large runs. At 

 such times population pressure forces some of the pinks to continue 

 on to the red-salmon spawning grounds. In years when the number 

 of pinks on the red-salmon spawning grounds is not large, no harm 



