However, further evidence was required on distribution 

 of salmon in spring (winter in the sea) when the colder water 

 of the North Pacific extends as far south as about 40° N. 

 Arrangements, therefore, were made for vessels from the 

 laboratory of the Bureau of Commercial Fisheries at Hono- 

 lulu to extend their spring cruise for tuna into waters north 

 of 40° N. and, as predicted, salmon were found in these 

 waters. It was evident that the distribution of salmon was 

 intimately associated with conditions in the ocean, varying 

 from season to season and, of course, from year to year. 



Coupled with this knowledge of the southern limit of sal- 

 mon distribution, subsequent studies have shown that the 

 northern limit lies at a temperature of about 3° C, and here 

 again the temperature pattern varies markedly between 

 seasons and years. 



Yearly changes in abundance of salmon have be en followed 

 closely since 1955 by fishing the sajiae stations on the high 

 seas. In this work we discovered that the numbers, kinds, 

 and sizes of salmon on the high seas vary from time to time 

 and place to place. For example, we have found the ocean 

 near the central Aleutian area to be heavily poptilated with 

 pink salmon {Oncorhynchus gorbuscha) during odd-numbered 

 years, and we have found that these are Asian fish. In marked 

 contrast, very few pink salmon are present in the even- 

 numbered years, and these fish are predominantly of North 

 American origin. Pink salmon invariably return to spawn at 

 the end of their second year of life, hence these patterns are 

 not surprising. 



The distribution of salmon within this area varies as the 

 season progresses. In 1959 pink salmon were first observed 

 in large numbers about 200 miles south of the Aleutian chain. 

 As the summer progressed, pink salmon became more and 

 more abundant near and north of the Aleutian chain in the 

 Bering Sea, but by mid-Jxily they co\ild be found only in the 

 westernmost part of the ocean, near the Asian continent. 



Similar changes have been foundfor red salmon (0. nerka). 

 In May and Jxine of 1959, the central area just north of the 

 Aleutians was heavily populated with adult red salmon almost 

 certainly of Bristol Bay origin, and red salmon remained 

 abundant here until about the end of June, In July, the larger, 

 more mature red salmon became scarce but we began to 

 catch large numbers of immature red salmon. In 1959 

 these immature red salmon were about 10 times more 

 abundant than in previous years and were certainly part of 

 the very large outmigration of small fish from Bristol Bay 

 in 1958. 



These initial explorations were sufficient to give us an 

 answer to the first question posed by the Protocol, that is, 

 did Asian and North American salmon intermingle on the 

 hign seas? There is no question but that large numbers of 

 salmon from Asia and North America intermingle in the 

 mid- Pacific and the Bering Sea. We also found that the 

 amount of mixing and the actual distribution of the salmon 

 was related to the abundance of fish from certain mainland 



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