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Fishery Bulletin 94(3). 1996 



Trolling gear 



We fished with reduced-size replicates of commer- 

 cial trolling gear. These small hooks and lures have 

 proven more selective than standard commercial 

 trolling gear in catching smaller sizes and younger 

 age groups of chinook salmon (Orsi, 1987). The hooks 

 were single Mustad no. 9510X3S, size 2/0, barbed, 

 gap 1.6 cm, throat 2.0 cm. All lures used were 6.0-cm 

 hootchies (plastic imitation squid) fished behind 9 x 

 28-cm flashers at 0.5-1.5 m/s and typically at 7.3-m 

 depth intervals (7.3 m, 14.6 m, 21.9 m, 29.3 m, and 

 36.6 m ). Five flasher and hootchie combinations were 

 used concurrently on each of four trolling lines 

 weighted with 13.6-22.7-kg lead "cannonballs." Ar- 

 eas where the bottom depth was shallower than 37 

 m were not sampled. Additional information on troll- 

 ing methods or gear is given in Browning ( 1980) and 

 Orsietal. (1987). 



To test whether the catch and size distribution of 

 the youngest age group of chinook salmon in our 

 study were representative of the population, we com- 

 pared the catch and length of prerecruit chinook 

 salmon caught on our standard small gear versus 

 the catch and length of prerecruit salmon caught on 

 smaller hooks (Mustad no. 9321, size 6, gap 0.7 cm, 

 throat 1.0 cm) and hootchies (4.0 cm). We tested this 

 for two days during September 1987 in inside wa- 

 ters of the southern region, where chinook salmon 

 are known to occur during their first summer at sea. 

 Equal numbers of each gear size and color were used 

 on opposing vessel sides at equivalent depths; sides 

 of the vessel were alternated each day. A chi-square 

 (X 2 ) test was used to test for significant differences 



(P<0.05) in catch between gear sizes, 

 and a one-tailed t-test was used to test 

 for significant differences (P<0.05) in 

 the mean fork length of chinook salmon 

 caught between gear sizes. 



Fish processing 



Chinook salmon were sampled while 

 immobilized in an electric basket (Orsi 

 and Short, 1987). While in the basket 

 and lifted from the water, fish were 

 identified, measured from tip of snout 

 to fork of tail (to the nearest cm), tagged 

 with a 6.4-cm-long Floy anchor tag (to 

 ensure that fish had not already been 

 caught), and sampled for scales from the 

 preferred area (INPFC, 1957). All 

 chinook salmon were released after tag- 

 ging, except adipose-clipped fish under 

 the Alaska minimum size limit (66 cm 

 fork length [FL]=71 cm total length; Reed, 1972), 

 which were retained to recover previously implanted 

 CWT's ( Jefferts et al., 1963). Sex and weight (to the 

 nearest 0.1 kg) were recorded for all retained CWT 

 chinook salmon. 



Because field identification between chinook 

 salmon and coho salmon, O. kisutch, in their first 

 ocean year is sometimes difficult, salmon identifica- 

 tions during the charters in September were con- 

 firmed later by a scale reader. Identifications that 

 did not correspond to the determinations of species 

 by the scale reader were reexamined and reassigned 

 as appropriate. Salmon with CWT's were also used 

 to corroborate species identifications. 



Scale, age, and sex analysis 



Scales of chinook salmon were aged according to the 

 methods of Van Alen and Wood ( 1983 ) and designated 

 with the nomenclature of Koo ( 1962). The end of the 

 calendar year was used as a break point for ocean- 

 age assignment. For example, a 1984-brood-year 

 chinook salmon that entered saltwater in 1986 was 

 designated to be age 1.0 until 31 December 1986 and 

 age 1.1 from 1 January to 31 December 1987. h Dis- 

 tinguishable ocean-winter annuli were present in 

 scales taken from fish in February. 



Data on age -.3 chinook salmon were not presented 

 because few were caught; the hooks used in this study 



fi Numeral preceding the decimal point denotes the number of 

 freshwater winters and the numeral following the decimal point 

 denotes the number of marine winters. A dash before the deci- 

 mal point indicates freshwater ages of and 1. 



