FISHERY BULLETIN: VOL. 71, NO, 3 



area and, for the most part, restricted to early 

 fall. The areas fished and the catch per set are 

 shown in Figure 4. The Japanese did not 

 engage in any fishing activity on the high seas 

 in the fall. As a result, no information was 

 available on steelhead trout in the far western 

 North Pacific Ocean or Okhotsk Sea in that 

 season. 



Although the data are meager, steelhead trout 

 continued to be found as far north and west as 

 the central Aleutian Islands area in early fall. 

 The catch of 0.90 steelhead trout per set in that 

 area was only slightly less than the NMFS 14- 

 yr catch average of 1.03 steelhead trout per gill 

 net set. 



Larger catches were made in the north- 

 eastern Pacific (east of long. 150 °W, south of 

 lat. 54 °N) than in the Aleutian Islands area, 

 averaging 2.9 fish per set and exceeding some- 

 what the relative abundance of steelhead trout 

 in the same area in the winter. The increased 

 catches in the northeastern Pacific area, together 

 with the return of spawning adults to the 



coastal waters and streams from southeast 

 Alaska to central California, indicate a general 

 shift of the population south and east in the late 

 summer, fall, and early winter. 



OCEANIC DISTRIBUTION OF 



STEELHEAD TROUT IN RELATION 



TO SURFACE TEMPERATURE 



Catch records and temperature data from 

 Canadian, Japanese, and the United States 

 (NMFS and FRI) research vessels showed a 

 relation of ocean distribution of steelhead trout 

 to surface water temperatures. Catches were 

 made in areas with surface water that ranged in 

 temperature from 5° to 14.9° C the majority 

 (61%) were in areas with surface water of 8° 

 to 11.4°C (Table 7.). The data strongly suggest 

 that the limits of steelhead trout distribution 

 conform closely to the 5°C isotherm on the 

 north and the 15°C isotherm on the south. Very 

 few steelhead trout were caught in areas where 



Figure 4. — Oceanic distribution and relative abundance of steelhead trout in fall (October-December). Catch and effort 

 data from gill net, longline, and purse seine sets by research vessels of Canada (1961-67), Japan (1955-57, 1962-67), and 

 the United States (1953, 1955-67). 



800 



