Figure 6. — Vertical sections of temperature along long. 

 177° 30' W., spring 1968. (Latitudinal positions 

 of stations are not to scale.) 



at long. 175° W. From these features we con- 

 cluded that the axis of the Alaskan Stream was 

 around lat. 53°30' N. 



The preceding detailed oceanographic data 

 were used to identify boundaries of various 

 major oceanographic features in the North 

 Pacific Ocean (Alaskan Stream, Ridge, West- 

 ern Subarctic, and Transition Water Areas). 

 Definitions of these Areas have been given by 

 McAlister, Ingraham, Day, and Larrance 

 (1970). These authors separated the Western 

 Subarctic water into two Areas, the Oyashio 

 Extension and Subarctic Current. Because 

 some oceanographers question this separation, 

 we have considered the Western Subarctic 

 water as one Area. 



DISTRIBUTION OF SALMON AS 



RELATED TO 



OCEANOGRAPHIC FEATURES 



Table 1 gives salmon catches by the three 

 research vessels by species for each set. In 

 the following discussion and illustrations of 

 distribution, catches have been standardized 

 by converting them to catch per tan in which 

 equal weight was given to each mesh size. 



Sockeye Salmon 



Figure 8 shows relative abundance of sock- 

 eye salmon as shown by gill net catches and 

 the location of ocean currents and Areas. Sock- 

 eye salmon were not taken south of lat. 46° N. 

 They extended northward to at least lat. 50°30' 



N., south of the western Aleutian Islands, to 

 lat. 51° N., south of the central Aleutians (see 

 longline catches, table 1), and to lat. 53° N., 

 south of the eastern Aleutians. They extended 

 southward on this easternmost cruise track to 

 at least lat. 49° N. 



The distribution of immature sockeye salmon 

 from north to south was relatively narrow 

 compared with that of maturing fish and was 

 restricted to the southern part of this range. 

 In relation to oceanographic features, they 

 were in the Western Subarctic and Transition 

 or easterly moving waters. 



Maturing sockeye salmon had a wider and 

 more northerly distribution than the immatures 

 and were in the Western Subarctic and Ridge 

 Areas; two maturing sockeye salmon were also 

 taken in Transition water along long. 175° E. 

 In relation to direction of water movement, 

 some maturing fish (particularly in the west) 

 were in easterly moving water and some ( par- 

 ticularly in the east) were in the weak, variable 

 currents of the Ridge Area. 



South of the central Aleutian Islands, only 

 two small catches of maturing fish were made 

 by gill nets, which indicated that abundance 

 of maturing fish was low in this area compared 

 to areas to the east and west. Longlines, how- 

 ever, took maturing sockeye salmon more con- 

 sistently along long. 175° W. (table 1), which 

 shows that relative abundance probably was 

 not as low in this area as was indicated by 

 gill net catches. 



Maturing and immature sockeye salmon 

 were also separated in the winter along long. 

 162° W. and 155° W. (French, Craddock, Bak- 

 kala, and Dunn, 1967) — immature fish were 

 primarily in the western Subarctic waters and 

 maturing fish in the Ridge Area. Distribution 

 of maturing and immature fish along long. 

 164° W. in spring 1968 was similar to the 

 distribution in winter. 



Maturing sockeye salmon were farther north 

 in early June than in May; they were concen- 

 trated in the Alaskan Stream and northern 

 part of the Ridge Area (fig. 9). These fish 

 were believed to be the Bristol Bay sockeye 

 salmon on their spawning migration. The main 

 part of this migration appeared to take place 

 from June 1 to 10; catches were relatively 

 much lower from June 10 to 15. 



