PROGRESS IN BIOLOGICAL INQUIRIES, 1934 365 



cial catch of pink salmon in this section durinjj the past season was 

 the greatest in the history of the fishery. This, however, does not 

 imply that these populations of salmon are no longer in need of 

 constant observation for past experience has shown that they are 

 subject to serious injury due to changes in both economic and natu- 

 ral conditions regardless of their state of abundance. Hence to 

 secure infornuition in regard to the changing status of these salmon 

 populations which will lead to their conservation so as to provide 

 for a }xn-manent and ])roductive fishery is the primary aim of the 

 pink-salmon investigation. 



The activities of this investigation in 1934, as in past years, were 

 confined to a study of the pink-salmon populations in southeastern 

 Alaska. Owing to the varied environmental conditions under which 

 the pink salmon reproduce in this section of the Territory, it is be- 

 lieved that the fundamental facts secured from the study of its 

 fishery may be applied generally to pink-salmon fisheries of Alaska. 

 Dr. Frederick A. Davidson is in charge of the investigation, assisted 

 by S. J. Hutchinson. 



A paper on the homing instinct and age of maturity of the pink 

 salmon was published during the past year. The evidence to date 

 indicates that the pink salmon have a great desire to return to spawn 

 in the streams from whence they came, but that some straying of the 

 adults may occur in localities where a number of streams are in close 

 proximity to each other. The evidence thus far collected also indi- 

 cates that the pink salmon have a complete 2-year life cycle, that is, 

 they invariably return to spawn at the close of their second year of 

 life. The results from the racial analysis of the pink salmon which 

 have been completed to date, substantiate the evidence in regard to 

 the age of maturity of the pink salmon. These results indicate that 

 2 distinct salmon populations are found in the streams, 1 that spawns 

 in the odd years and 1 that spawns in the even years. 



A continuous study is being made of the yearly fluctuations in the 

 abundance of the pink salmon in southeastern Alaska beginning with 

 the inception of the industry in 1895. The results from this study 

 show that wide fluctuations may be expected in the yearly abundance 

 of these salmon. Since the pink salmon have a complete 2-year life 

 cycle, the number that return to spawn any year is the result of a 

 single spawning brood and not of several broods as in the case of the 

 red salmon. Hence a marked change in the mortality of any brood 

 is directly reflected in the number of salmon that return 2 years later. 

 Knowing the disastrous effects that lack of rainfall during the spawn- 

 ing period can have upon the success of a spawning po])ulation, it is 

 not surprsing to find these wide fluctuations in the yearly abundance- 

 of the pink salmon. The amount and time of occurrence of rainfall, 

 however, are not the only factors which influence the mortality of 

 the spawning salmon and subsequent brood. Hence a study is being 

 made for the purpose of determining and evaluating all of the factors 

 which influence the mortality of the salmon during their entire cycle 

 of repix)duction. 



This study was started in the stream at Olive Cove, Alaska, but 

 OAving to handicaps encountered there it was transferred to the stream 

 at Little Port Walter in the summer of 1934. The stream at Little 

 Port Walter provides a very satisfactory location for this study. 



