Unusual changes in the abundance of salmon usually 

 accompany changes in water properties, structure, or flow. 

 The abundance of sockeye salmon and of minute organisms 

 is apparently related to the major oceanographic features 

 in the Pacific Subarctic, south of the Aleutian Islands (fig. 8) . 



During the summer, immature sockeye salmon were 

 caught south of Adak Island — in an area with no well- 

 defined currents, or the Ridge Area, just south of the Alaskan 

 Stream. During the winter, immature sockeye salmon were 

 farther south in the extension of the Western Subarctic 

 water. Maturing sockeye salmon, on the other hand, were 

 found only in the Alaskan Stream and in the Ridge Area. 

 Maturing fish apparently remain in more northerly waters 

 in the winter before their spawning migration. 



FIGURE 5.— Bureau's newest research vessel, the 215-foot 

 Miller Freeman was launched in 1967. She carries 9 scientists 

 and a crew of 28. Her cruising speed is 14 knots, and max- 

 imum range is 16,000 miles. 



FIGURE 6.— Sockeye salmon caught by a gill net. In the water, 

 fish are captured when they push their heads through a mesh 

 opening. When the twine constricts them behind the gill 

 covers, they find it difficult to escape. 



Chum salmon apparently move with the Alaskan Gyre 

 in late spring and summer and appear in the Subarctic Cur- 

 rent in winter. Several species of salmon were caught in 

 significant numbers in the strong Subarctic Current in the 

 winter cruise of 1967, but apparently they were not south 

 of the main a.xis of that current and only in small numbers 

 in the Ridge Area to the north. 



Summer cruises in 1966-68 examined the distribution 

 of salmon in the central Aleutian Islands area in relation 

 to oceanic features. The area has been an imjiortant site 

 for obtaining indexes of the abundance of immature fish • — 

 in forecasting the run to Bristol Bay the following year. 



5 — 



