Hooking Mortality of Chinook Salmon Released by Commercial Trollers

Abstract

Immediate and short-term (1–5-d) hooking mortality associated with the incidental catch of chinook salmon Oncorhynchus tshawytscha was assessed during periods when troll fishing for that species (only) was prohibited. Two chartered power trollers fished their normal complements of gear directed at coho salmon O. kisutch in Hawk Inlet, southeastern Alaska. Wound location, fork length, and lure type were the factors principally associated with mortality of incidentally caught chinook salmon. Severity of the hooking wound was also related to mortality. Maximum-likelihood estimates (with 95% confidence intervals in parentheses) of total mortality were 24.5% (20.1–29.0%) for sublegal-sized (<66 cm fork length) chinook salmon and 20.5% (9.0–31.9%) for legal-sized chinook salmon. The delayed-mortality rates were used to recalculate hooking mortality estimates from previous tagging experiments in which it was assumed that no delayed mortality occurred for certain locations and severities of wounds. The recalculated estimate of total hooking mortality for sublegal fish, based on wound location, was 25.7%. The recalculated estimate of total hooking mortality for legal and sublegal fish, based on wound severity, was 23.5%.