Orsi and Jaenicke Marine distribution and origin of prerecruit Oncorhynchus tshawytscha 



489 



70 

 BO 



1 5 °H 



—■ 



40 - 



a> 



O 30 



Legal size 



e 



(540' iBS9) |776) 



111 



02 02 



C) 



□ Ocean-type rh "_ , a " 9e 



+4+ -^ — Mean 



-Range 



 Mean 



□ Stream-type ' "^Standard 

 deviation 



'~^\ 



~\ — r 



F,-: 



-i — r- 



F. I 



May 



— I 1- 



Sep 



Age - 



Age - 1 



Age -2 



Figure 3 



Length at age for ocean- and stream-type chinook salmon, 

 Oncorhynchus tshawytscha, sampled in marine waters of south- 

 eastern Alaska during February 1987, May 1986-87, and Sep- 

 tember 1986-87. Sample sizes are in parentheses. 



in outside waters; conversely, age -.1 and -.2 

 ocean-type fish were almost exclusively from 

 British Columbia, Washington, or Oregon stocks 

 and were caught at a slightly higher rate in out- 

 side waters (Fig. 4). 



The CPUE of chinook salmon originating from 

 each geographic region changed seasonally for 

 each ocean-age group (Fig. 5). Age -.0 chinook 

 salmon, which were caught only in September, 

 were mainly of Alaska origin. All age -.1 chinook 

 salmon in February were of Alaska origin ex- 

 cept a few fish from British Columbia in inside 

 waters (Fig. 5; Table 6). Among age -.1 fish 

 caught in May, increasing numbers offish from 

 non-Alaska stocks were present; however, most 

 of the fish were still of Alaska origin (Fig. 5). 

 By September, an influx of age -.1 chinook 

 salmon from British Columbia, Washington, or 

 Oregon occurred, whereas the catches of age 

 -. 1 fish of Alaska origin diminished ( Fig. 5 ). Most 

 age -.2 chinook salmon were also from non- 

 Alaska stocks for all periods. 



Migration and growth 



Assessment of migration direction and rates of 

 the CWT chinook salmon was based on the origin 

 and age of the stock group (Table 7). Stocks originat- 

 ing from British Columbia and Washington or Or- 

 egon generally traveled NW or N to reach our sam- 

 pling localities, whereas stocks originating from 



I i -•. . i- - 



1 I British Columbia 

 ^m Washington 

 ^* or Oregon 



(126) 



2) 



i3il|n°i 



Inside waters 



n = 2090 (4561 



(31) 



(4) I2) |-| 13) 



(1^1 V"' 



LH 



Outside waters 



n = 486 (83) 



id is) n (2) 



_a m U — □_ 



00 



i 



02 



1 



1 1 



1 2 



Ocean-type age 



Stream-type age 



Figure 4 



Catch rate by age and origin of ocean- and stream-type chinook 

 salmon, Oncorhynchus tshawytscha, in inside and outside ma- 

 rine waters of southeastern Alaska, 1986-87. Catch rate is based 

 on the expanded numbers of coded-wire— tagged fish caught per 

 hour. Actual numbers of coded- wire-tagged fish are shown in pa- 

 rentheses. 



within southeastern Alaska had no apparent direc- 

 tional tendency. Average net migration rates ranged 

 from 0.1 to 6.9 km/d (Table 7). A decrease in average 

 migration rates with increasing age occurred for all 

 stock groups of ocean- and stream-type fish. 



