Marine distribution and origin of prerecruit chinook salmon, Oncorhynchus tshawytscha, in southeastern Alaska

Chinook salmon, Oncorhynchus tshawytscha, <71 cm total length, are typically not retained in directed marine fisheries of southeastern Alaska because of size restrictions; consequently, little is known of the origin or temporal and spatial distribution of these prerecruits. To obtain such data, commercial power trollers were chartered 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 February, May, and September 1986-87, a total of 5,838 prerecruit chinook salmon were caught, of which 539 contained coded-wire tags with information on stock origin. Age -.O chinook. salmon were caught in September during their first year at sea; they originated 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, Washington, 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 during 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 marine waters of southeastern Alaska as a nursery area for an amalgam of prerecruit chinook salmon stocks originating between Oregon and southeastern Alaska, a range of 1,800 km.