Adult stock 

 C 



Drift 



Spawning area 



Figure 79. — The annual circuit of migration (Harden Jones 1968) 



Nursery area 



during summer, large areas of residual subzero winter bottom 

 water remain on the northern central shelf. Faced with potentially 

 lethal conditions, Bering Sea Fishes use two principal mechanisms 

 to avoid freezing: Behavioral avoidance (i.e., seasonal migration) 

 and production of biochemical antifreezes. Whereas some of the 

 major fish populations must apparently undergo regular seasonal 

 migrations from shallow to deep water (e.g., yellowfin sole, 

 Pacific halibut, Alaska plaice), other taxa develop glycoprotein 

 and protein antifreezes (e.g., saffron cod and sculpins such as 

 Myoxocephalus spp.) (Raymond et al. 1975) that apparently 

 enable survival in all regions of the continental shelf throughout 

 the year. 



Figure 80 shows two measures of climatic conditions in the 

 southeastern Bering Sea during the period 1966-77 (McLain and 

 Favorite 1976: figure 1 updated to 1977 with data from the 

 authors; International Pacific Halibut Commission 1976 see foot- 

 note 8, 1977'). Like most climatic data, both time series indicate 

 extended multiyear periods of warm or cold conditions, rather 



'International Pacific Halibut Commission. 1977. Items of information on 

 the halibut fishery in the Bering Sea and the northeastern Pacific Ocean. Unpubl. 

 manuscr., 39 p. International Pacific Halibut Commission, P.O. Box 5009, 

 University Station, Seattle, WA 98105. 



ANOMALY OF SEA SURFACE TEMPERATURE 



1966 I 1967 | 1968 | 1969 | 1970 I 1971 I 1972 | 1973 | 1974 | 1975 1976 1977 



B 



MEAN BOTTOM WATER TEMPERATURE 



5- 

 4- 



»C 3 " 



2- 

 I- 

 



1966 



1967 



1968 



1969 



1970 



1971 



1972 



1973 



1974 



1975 



1976 



1977 



Figure 80. — Climatic conditions in the southeastern Bering Sea 1966-77: A) anomaly of sea surface temperature at lat. 57 °N, long. 170 °W (near St. Paul 

 Island) from the April 1962-May 1975 mean; B) mean bottom water temperature during June at 34 standard International Pacific Halibut Commission 

 survey stations in the southeastern Bering Sea. 



Ill 



