PROGRESS IN BIOLOGICAL INQUIRIES, 1931 475 



catch was sampled for the return of fish marked in 1928, 1929, 

 and 1930. 



In 1930, 55,000 migrants were marked, 50,000 by the removal of 

 one ventral fin and the adipose fin and 5,000 by the removal of the 

 right pectoral fin and the adipose fin. This was the first time the 

 pectoral mark had been used at Karluk. The first returns from 

 this marking appeared this year, and it is of interest to note that 

 the returns of fish marked by the removal of the right pectoral fin 

 and the adipose fin were comparable to the returns of the fish 

 marked by the removal of one ventral fin and the adipose fin; there- 

 fore, it appears that the use of this mark will prove to be satis- 

 factory. 



The study of the returns from known escapements of spawning 

 salmon was continued. The run of 1931 was, for the main part, 

 the return from the brood year of 1926. The escapement of 1926, 

 2,500,000 fish, was the greatest escapement of red salmon into Kar- 

 luk River of which we have any record; and had conditions on the 

 spawning grounds been favorable, a very large run in 1931 un- 

 doubtedly would have been produced. The run in 1931 was, how- 

 ever, only fair. That conditions on the spawning grounds were not 

 favorable was noticed by observers in 1926, and their observations 

 were included in the first Karluk report, " Investigations concerning 

 the red salmon runs to the Karluk River, Alaska," by Charles H. Gil- 

 bert and Willis H. Rich, in which it was stated in regard to the low 

 water in the Karluk River watershed, " * * * J^st what effect 

 this will have on the success of the spawning is problematical; it 

 may be slight or it may be great enough to offset in considerable 

 measure the effect of the fine spawning escapement * * *." 



We have, then, two brood years which are somewhat comparable — 

 1924 and 1926. In 1924 the red-salmon escapement was about 

 1,000,000 fish and the pink-salmon escapement was estimated at over 

 4,000,000 fish, the pink salmon occupjang to a great extent the same 

 spawning grounds as the red salmon. The spawning beds were so 

 crowded, due to the very large escapement, that the result of the 

 spawning was poor. Only a few thousand pink salmon returned to 

 Karluk in 1926 from the spawning escapement of over 4,000,000 

 fish, and the return of red salmon from this brood year was less than 

 1 to 1. Overcrowding on the spawning grounds was undoubtedly the 

 chief cause of the poor returns. 



The summer of 1926 was unusually dry at Karluk, resulting in a 

 lowering of the level of the spawning streams entering into Karluk 

 Lake and also a lowering of the level of the lake itself. Thus the 

 area of the spawning beds was reduced, and the good escapement of 

 2,500,000 red salmon caused overcrowding on the spawning grounds. 

 Both in 1924 and 1926 there was noticeable overcrowding, and in 

 both cases the return from the spawning escapement was less than 

 1 to 1. We are faced, then, with the evidence that too large an 

 escapement is just as unfortunate as too small an escapement. 



It must be pointed out here, however, that the evidence can not be 

 interpreted to mean that every time there is an escapement of 

 2,500,000 red salmon into Karluk River that there will be a poor 

 return, for if climatic conditions at Karluk Lake had been normal 

 in 1926, the spawning grounds would not have been overcrowded. 



