Abstract.- Over the past sever- 

 al years researchers in Japan and the 

 United States have independently 

 been conducting extensive studies on 

 the early life history of two discrete 

 populations of walleye pollock Thera- 

 gra chalcogramma, trying to under- 

 stand recruitment variation. The 

 population of interest to Japanese 

 researchers spawns near Funka Bay, 

 Hokkaido, Japan, while the popu- 

 lation of interest to American re- 

 searchers spawns in Shelikof Strait, 

 Gulf of Alaska. This paper summar- 

 izes and compares characteristics of 

 spawning and ecology of eggs, lar- 

 vae, and early juveniles of the spe- 

 cies in these two areas. Although the 

 species has apparently adapted its 

 early-life-history pattern to environ- 

 mental differences in the two areas, 

 some underlying similarities exist. 

 The adults mainly spawn at a partic- 

 ular time of year following a spawn- 

 ing migration to a specific location 

 so that the eggs and larvae can reach 

 specific areas for subsequent devel- 

 opment. In both areas oceanographic 

 conditions are favorable for larval 

 food production (copepod nauplii) 

 when the walleye pollock larvae are 

 present. Drift of the eggs into the 

 bay, where copepod production is 

 enhanced, seems important in Funka 

 Bay, and drift of the larvae toward 

 juvenile nursery grounds on the con- 

 tinental shelf as opposed to being 

 swept offshore, seems important in 

 Shelikof Strait. Interannual differ- 

 ences in larval drift and food pro- 

 duction because of varying oceano- 

 graphic conditions may contribute 

 significantly to variations in year- 

 class size. 



Comparisons of early-life-history 

 characteristics of walleye pollock 

 Theragra chalcogramma in 

 Shelikof Strait, Gulf of Alaska, 

 and Funka Bay, Hokkaido, Japan* 



Arthur W. Kendall Jr. 



Alaska Fisheries Science Center, National Marine Fisheries Service. NOAA 

 7600 Sand Point Way NE, Seattle, Washington 981 15-0070 



Toshikuni Nakatani 



Laboratory of Principles of Fishing Grounds, Faculty of Fisheries 

 Hokkaido University, Hakodate, Japan 041 



Walleye pollock Theragra chalcogram- 

 ma is a dominant fish in the North 

 Pacific Ocean and in the Bering Sea, 

 both in terms of population size and 

 importance to commercial fisheries. 

 It is a major fishery resource in the 

 Funka Bay area on the Pacific Ocean 

 side of Hokkaido, Japan, and in Sheli- 

 kof Strait, Gulf of Alaska. In both 

 areas, most fishing is done just prior 

 to and during the spawning season. 

 In Funka Bay, walleye pollock are 

 caught in bottom gillnets, while in 

 Shelikof Strait midwater trawls are 

 used. In Funka Bay the catch varied 

 from about 4.3x10^ metric tons (t) 

 to about 10.7x10-4 t from 1976 to 

 1986. In Shelikof Strait, an intense 

 fishery on the spawmers existed from 

 1981 through 1988, although harvest 

 has been severely restricted since 

 1986 because of reduced abundance 

 of the population (Megrey 1989). The 

 harvest in Shelikof Strait peaked in 

 1984 at about SlxlC* t. 



There is a growing interest in 

 understanding recruitment in this 

 species, and considerable work has 

 been conducted independently by 

 Japanese researchers in Funka Bay 

 and by U.S. researchers in Shelikof 

 Strait over the past several years. 



Manuscript accepted 27 November 1991. 

 Fishery Bulletin, U.S. 90:129-138 (1992). 



* Contribution FOCI- 138 to Fisheries Oceanog- 

 raphy Coordinated Investigations, NOAA. 



This paper compares the results of 

 these studies (Table 1). While these 

 studies reveal that the early-life- 

 history strategy of walleye pollock 

 allows this species to adapt to differ- 

 ent environments, they also indicate 

 that underlying similarities exist be- 

 tween populations. Although under- 

 standing causes of recruitment varia- 

 tion in either area is a distant goal, 

 testable hypotheses have been devel- 

 oped in both areas. The comparisons 

 presented in this paper may help 

 researchers in both areas focus their 

 studies toward an understanding of 

 the recruitment process. They may 

 also guide future studies of the spe- 

 cies in other areas such as the Ber- 

 ing Sea. 



Environmental 

 comparisons 



Physical setting 



Funka Bay is located in the southern 

 part of Hokkaido, Japan, at about 

 42°N (Fig. 1). Depths within the bay 

 are generally less than 80 m, although 

 there is a small area of water deeper 

 than 100 m in the center of the bay. 

 Immediately outside the bay the bot- 

 tom slopes evenly to 500 m within 

 45km. The area of the bay is 2270 

 km2. 



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