482 



AbStr3Ct.- Chinook salmon, Onco- 

 rhynchus tshawytscha, <71 cm total 

 length, are typically not retained in di- 

 rected marine fisheries of southeastern 

 Alaska because of size restrictions; con- 

 sequently, little is known of the origin 

 or temporal and spatial distribution of 

 these prerecruits. To obtain such data, 

 commercial power trollers were char- 

 tered to fish for small chinook salmon 

 with small hooks and lures within the 

 Alexander Archipelago (inside waters) 

 and the adjacent coastal region (outside 

 waters). During the 135-d study in Feb- 

 ruary, May, and September 1986-87, a 

 total of 5,838 prerecruit chinook sal- 

 mon were caught, of which 539 con- 

 tained coded-wire tags with informa- 

 tion on stock origin. Age -.0 chinook 

 salmon were caught in September dur- 

 ing their first year at sea; they origi- 

 nated predominately from stream-type 

 stocks of southeastern Alaska. Age -.1 

 chinook salmon in February and May 

 were primarily from stream-type stocks 

 of southeastern Alaska; however, by 

 September most were from ocean-type 

 stocks from British Columbia, Wash- 

 ington, and Oregon streams. Most age 

 -.2 chinook salmon were from ocean- 

 type stocks of southern origin. Average 

 net marine migration rates of different 

 chinook salmon age groups ranged from 

 0.1 to 6.9 km/d; the highest rates were 

 for age 1.0 fish from Washington and 

 Oregon. For coded-wire-tagged chinook 

 salmon of the same ocean age group, 

 growth rates of ocean-type fish were 

 significantly (P<0.05) higher than 

 growth rates of stream-type fish dur- 

 ing most periods. Spatial distribution 

 also differed by race: stream-type fish 

 predominated in inside waters and 

 ocean-type fish in outside waters. This 

 study identifies the importance of ma- 

 rine waters of southeastern Alaska as 

 a nursery area for an amalgam of pre- 

 recruit chinook salmon stocks originat- 

 ing between Oregon and southeastern 

 Alaska, a range of 1,800 km. 



Marine distribution and origin of 

 prerecruit chinook salmon, 

 Oncorhynchus tshawytscha, in 

 southeastern Alaska 



Joseph A. Orsi 

 Herbert W. Jaenicke 



Auke Bay Laboratory, Alaska Fisheries Science Center 



National Marine Fisheries Service, NOAA 



I 1305 Glacier Highway, Juneau, Alaska 99801-8626 



Manuscript accepted January 29 1996 

 Fishery Bulletin 94:482-497 ( 1996). 



Alaskan and non-Alaskan stocks of 

 chinook salmon, Oncorhynchus 

 tshawytscha, are harvested in 

 southeastern Alaska waters pre- 

 dominately in hook-and-line marine 

 fisheries; however, owing to a mini- 

 mum size restriction of 71-cm total 

 length, limited information exists 

 on the temporal and spatial occur- 

 rence of smaller fish (prerecruits). 

 Many North American stocks of 

 chinook salmon embark on exten- 

 sive marine migrations along the 

 eastern Pacific Rim (Mason, 1965; 

 Hartt and Dell, 1986). Some mi- 

 grate across international or state 

 boundaries and are intercepted in 

 fisheries along migration corridors 

 or in distant nursery areas. Conse- 

 quently, many chinook salmon 

 stocks have been overexploited, and 

 rebuilding depressed runs is a ma- 

 jor concern identified in the 1985 

 U.S. -Canada Pacific Salmon Treaty 

 (Pacific Salmon Commission, 1986). 

 A better understanding of the ma- 

 rine life history and distribution of 

 chinook salmon populations will 

 contribute to the development of 

 management policies that are needed 

 to restore the depressed stocks. 



Not all chinook salmon migrate 

 long distances. Some stocks in Or- 

 egon, Washington, British Columbia, 

 and southeastern Alaska apparently 

 do not migrate northward to any 

 great extent (Mason, 1965; Nicholas 

 and Hankin 1 ), and many remain in 



inside waters all or much of their 

 marine life (Hartt and Dell, 1986). 



Two distinct races of chinook 

 salmon have been identified: stream- 

 type and ocean-type ("sea-type") 

 (Gilbert, 1914; Healey, 1983). Stream- 

 type fish are found throughout the 

 geographic range of the species, 

 whereas ocean-type fish occur pri- 

 marily from British Columbia to 

 California (Major et al., 1978; 

 Healey, 1983). Stream-type chinook 

 salmon remain in fresh water for 

 one or more years before migrating 

 to an estuary, whereas ocean-type 

 chinook salmon migrate directly to 

 an estuary as newly emerged fry or 

 after 2-3 months of freshwater resi- 

 dence (Healey, 1983; Taylor, 1990). 

 Prior to ocean entry, stream-type 

 chinook salmon have a brief estua- 

 rine residence (Healey, 1983; Fisher 

 and Pearcy, 1990) in contrast to 

 ocean-type chinook salmon, which 

 may reside in estuaries for up to 

 three months (Healey, 1980; Myers 

 and Horton, 1982; Nicholas and 

 Hankin 1 ; Reimers 2 ). 



1 Nicholas, J. W., and D. J. Hankin. 1988. 

 Chinook salmon populations in Oregon 

 coastal river basins: description of life his- 

 tories and assessment of recent trends in run 

 strengths. Info. Rep. 88-1, Oregon Dep. 

 Fish Wildl.. Fish. Div, Res. and Develop. Sec- 

 tion, Portland, OR 97207, 359 p. 



2 Reimers, P. E. 1973. The length of resi- 

 dence of juvenile fall chinook salmon in 

 Sixes River, Oregon. Oregon Fish Comm. 

 Res. Rep. 4(2), Oregon Dep. Fish Wildl., 

 Portland OR 97201, 43 p. 



