FISHERY BULLETIN: VOL. 80, NO. 4 



VANCOUVER ISL 



Figure 1.— Areas in British Columbia where Fraser River chum salmon are caught in the commercial fish- 

 ery. Inset shows areas in the lower Fraser River where fry and returning adults were sampled. 



(1979 3 ). Briefly, the sampling procedure con- 

 sisted of suspending traps at various depths from 

 the surface to 3.7 m (12 ft) from either side of 

 a boat travelling at a constant velocity relative 

 to the water for 15-min periods. Samples were 

 taken in this manner between 0500 and 1300 h. 

 Preliminary sampling had established that 

 chum fry migrated past Mission City were most 

 active during this period. Sampling occurred 

 during this period, 5 d a week from beginning of 

 March to end of May. Daily sampling was con- 

 tinued for 24 h 2 or 3 d/ wk so that estimates of the 

 daily proportion of fry migrating during the stan- 

 dard shift (0500 to 1300 h) could be made, and 

 daily totals of chum fry migrating past Mission 

 City calculated. Sampling was also performed at 

 different sites across the 527 m (1,725 ft) width of 

 the Fraser River at Mission City. The depth and 



3 Bailey, M.D. 1979. Enumeration of salmon in the Fraser 

 River. Unpubl. manuscr., 122 p. Department of Fisheries 

 and Oceans. 



cross-sectional area of the river were known at 

 each sampling site, as well as the area sampled 

 by the fry traps, so that, by extrapolation, the 

 number of fry migrating downstream daily 

 could be estimated. Abundance of chum salmon 

 fry used in the present analysis was taken from 

 Bailey (footnote 3), as were the dates when 50% of 

 the chum and pink, O. gorbuscha, salmon fry 

 were estimated to have migrated past the sam- 

 pling site. Weekly mean lengths (mm) of fry were 

 determined in 1978. 



Sex ratios, age composition, length-at-age, and 

 fecundity of adult chum salmon arriving at the 

 river mouth were derived from test fishing con- 

 ducted at Cottonwood Drift from 1962 to 1979 

 and Albion from 1978 to 1979 (Fig. 1). A 274 m 

 (150-fathom) long, 60-mesh deep gill net having 

 16.9 cm (6% in) mesh was set for a standard 30- 

 min drift twice a day during the slack period of 

 the lowest tide of the day. Smaller fish may have 

 avoided capture on account of gill net selectivity 

 (McCombie and Berst 1969; Todd and Larkin 



814 



