Orsi and Jaemcke Marine distribution and origin of prerecruit Oncorhynchus tshawytscha 



483 



In marine waters of southeastern Alaska, chinook 

 salmon occur throughout the year (Cobb, 1910) and 

 are harvested principally in a commercial troll fish- 

 ery. Origins of stocks in this fishery are diverse, as 

 documented by marine tagging studies, coded-wire 

 tag (CWT) recoveries, and scale pattern analyses 

 (Parker and Kirkness, 1956; Clark et al., 1985; Van 

 Alen, 1988; Kissner 3 ; Funk 4 ). Throughout the history 

 of this fishery, ocean-type chinook salmon of non- 

 Alaskan origin have been the major harvest compo- 

 nent (Parker and Kirkness, 1956; Van Alen and Wood, 

 1983; Olsen, 1992). Surprisingly, relatively little is 

 known of the early marine distribution of prerecruit 

 ocean-type fish after the initial summer at sea 

 (Healey and Groot, 1987). In particular, it is not 

 known whether prerecruit chinook salmon of differ- 

 ent age groups within Alaskan marine waters are 

 primarily of Alaskan or non-Alaskan origin. 



Southeastern Alaska stocks of chinook salmon, 

 which are primarily stream-type (Van Alen et al., 

 1986), migrate through inside marine waters of 

 southeastern Alaska before their first marine win- 

 ter (Orsi et al., 1987). In the summer and fall after 

 their first marine winter, some portion of these stocks 

 are recovered in southeastern Alaska waters ( Hubartt 

 and Kissner, 1987), whereas others migrate offshore 

 to the North Pacific Ocean (Dahlberg et al. 5 ). To iden- 

 tify the temporal and spatial distribution of prerecruit 

 chinook salmon stocks in southeastern Alaska waters, 

 we used commercial salmon trailers with small hooks 

 and lures to sample prerecruits during February 1987 

 and May and September 1986 and 1987. 



Methods 



Sampling areas and times 



Southeastern Alaska comprises the mainland coast 

 and a large island group, the Alexander Archipelago, 

 which covers about 100,000 km 2 (Fig. 1). Marine 

 waters throughout this island group are a network 

 of estuaries, fjords, and straits that lead into the Gulf 



3 Kissner, P. D. 1977. A study of chinook salmon in Southeast 

 Alaska. Alaska Dep. Fish Game, Sport Fish Div. Completion 

 Rep.. Vol. 18, Project F-9-8, Study AFS-41-5, Juneau, AK, 63 p. 



4 Funk, F. 1981. Analysis of southeastern Alaska troll fisher- 

 ies data. Final Report, Contract 79-4, North Pacific Fishery 

 Management Council Document 17. Alaska Dep. Fish and 

 Game, Juneau, 103 p. + appendix. 



s Dahlberg, M., S. Fowler, N. Maloney, and R. Heintz. 1991 In- 

 cidence of coded-wire tagged salmonids in commercial and re- 

 search catches in the North Pacific Ocean and Bering Sea, 1990- 

 1991. ( INPFC [International North Pacific Fisheries Commis- 

 sion] Doc.),Auke Bay Laboratory, Alaska Fish. Sci. Cent., NMFS, 

 NOAA, 11305 Glacier Hwy, Juneau, AK 99801-8626, 17 p. 



V 1 Study 



V"* | area 



73 Alaska i I 



Inside waters 

 Outside waters 



Figure 1 



Inside and outside marine waters sampled in the northern, cen- 

 tral, and southern regions of southeastern Alaska, 1986-87. 



of Alaska or Dixon Entrance. We sampled chinook 

 salmon in "inside" and "outside" marine waters of 

 the northern, central, and southern regions of the 

 archipelago (Fig. 1). We defined "inside" waters as 

 those within the Alexander Archipelago, typically 

 adjacent to mainland southeastern Alaska, and "out- 

 side" waters as the coastal waters exposed to the Gulf 

 of Alaska or Dixon Entrance near the outer coasts of 

 Chichagof, Kuiu, and Prince of Wales Islands. Our 

 selection criteria for sampling areas and times were 

 influenced by the geographical localities of the ma- 

 jor fishing ports in southeastern Alaska and by the 

 availability of commercial trolling vessels during 

 three off-season fishing periods separated by about 

 four months. 



We sampled chinook salmon from 11.0-16.2-m 

 chartered commercial power troll vessels during May 

 and September 1986 and February, May, and Sep- 

 tember 1987 for a total of 1,156 h of fishing effort 

 over a 135-d period (Table 1). The vessels were oper- 

 ated by experienced commercial salmon trailers, ac- 

 companied by fishery biologists. Inside and outside 

 waters were typically sampled in each region and 

 season; however, the central region was sampled only 

 in September 1986, and inclement weather precluded 

 sampling the outside waters of the southern region 

 in February 1987 (Table 1). 



