Straying Patterns of Coho Salmon (Oncorhynchus kisutch) Stock from Southeast Vancouver Island, British Columbia

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Abstract
Fourteen coho salmon (Oncorhynchus kisutch) stocks of wild and hatchery origin were tagged from 1985 to 1988 in nine streams within a 150-km coastal section of Vancouver Island. Tag escapements to natal streams were estimated from fence counts, stream surveys, and mark–recapture operations. On average, adult (age 3+) strays accounted for ~4.7% of escapements, but for > 40% of the adult escapements in some cases. Adult straying rate, averaged across all years and stocks, was < 2%. Straying rates tended to be lower for hatchery fish and highest for stocks subjected to certain enhancement practices. Adult strays escaped to streams 2–159 km from their home stream (average 15.7 km); over 50% escaped to streams < 7 km from their stream of release. Straying rates of jacks (age 2+) in a given year and that of their adult siblings during the following year were not related. Genetic makeup, age-at-return, run timing, and exposure to nonnatal water sources during the rearing stage did influence homing. Changes in natural straying patterns should be suspected where enhancement measures include flow controls, selective breeding, and exposure of fry to various water sources. Straying levels and stray contributions should be considered when estimating survival and exploitation rates