ESCAPEMENT LEVELS AND PRODUCTIVITY OF THE NUSHAGAK 

 SOCKEYE SALMON RUN FROM 1908 TO 1966" 



OLE A. Mathisen'^ 



ABSTRACT 



Since the inception of a commercial fishery for soclteye sahnon in the Nushagak District, Bristol Bay, 

 Alaska, the annual yields have followed a definite pattern. Catches increased during a relatively short 

 development phase of the fishery, then stabilized for some years and then declined in two steps separated 

 by periods of relative stability. 



For years the cause of the decline had been thought to be overfi-shing, and various measures of cur- 

 tailment had been placed upon the fishing industry. 



Evidence is presented in this paper that the average escapement or the potential egg deposition re- 

 mained about the same during each of three periods (1908-1919, 192.5-1945, and 1946-1966) ; hence 

 the diminution in the runs was due not to lack of spawners but to a decline in the rate of return per 

 spawner. 



So that the cause or causes of the present low reproductive potential can be ascertained, the effects 

 of fishing on the stocks of salmon must be examined. Besides removing part of the run, the yearly 

 commercial fishing operation may have altered either the age composition or the distribution of the 

 escapement. 



Available historical records were examined for evidence of these types of changes but largely with 

 a negative result; therefore, the hj^pothesis was advanced that the observed declining rate of return 

 per spawner is caused by a declining basic productivity of the nursery areas. The latter is then ascrib- 

 able to the cumulative effect of relatively little enrichment of bioenergetic elements from salmon carcas- 

 ses since the instigation of commercial fishing operations in comparison with the prefishing era when 

 the entire virgin run escaped to the spawning grounds. 



Suggestions are made for future field testing of this hypothesis. 



In the development of the salmon fishery along 

 the eastern perimeter of the Pacific Ocean, the 

 most southern stocks were utilized first. As de- 

 mand increased and certain stocks declined, the 

 fishery shifted northward until the runs of the 

 entii-e southeastern Alaska and soon thereafter 

 those of the western districts were exploited. 

 The rapidity of growth of the salmon fishing in- 

 dusti'v in Alaska is astonishing. The firstcannery 

 was built in southeastern Alaska at Klawak in 

 1878 (Rich and Ball, 1928), and only 6 years later 

 exploratory fishing was conducted in Bristol Bay. 

 The early Bristol Bay catch records show that, 

 from 1884 to 1891, fishing was conducted only 

 in Nushagak Bay (Figure 1). Four years later, 

 salmon was harvested in the other watersheds 

 of Bristol Bay, the Kvichak-Naknek, the Egegik, 



' Contribution No. 346, College of Fisheries, University 

 of Washington. 



' Fisheries Research Institute, College of Fisheries, 

 University of Washington, Seattle, Wash. 98195. 



Manuscript accepted April 1971. 



FISHERY BULLETIN: VOL. 69, NO. 4. 1971. 



and the Ugashik Districts. The patterns were 

 initially alike, with a continuous and steady rise 

 in production for at least 10 years in the smaller 

 districts of Egegik and Ugashik and 20 years 

 or more in the Nushagak District and even longer 

 in the Kvichak District where on the average 

 more than 60 'r of the Bristol Bay harvest is 

 made annually. 



As these four fisheries developed, annual var- 

 iations became more and more aijparent, but the 

 overall iiroduction was fairly stable until 1919, 

 when it declined drastically all over Bristol Bay 

 in spite of no decline in fishing effort. The catch- 

 es in Ugashik, Egegik, and Kvichak Districts 

 soon thereafter rebounded to their former pro- 

 duction level, but the catches in the Nushagak 

 District did not. From this point on, the pattern 

 of development in Nushagak difl^ered from that 

 of the other fishing areas in Bristol Bay, primar- 

 ily in a more severe and persistent decline of the 

 stocks making up the entire run. 



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