Influence of gear type, release method, and injury on immediate and delayed mortality of Chinook salmon (Oncorhynchus tshawytscha) captured and released from a marine recreational fishery

Capture and release (CR) is a management strategy increasingly employed in Pacific salmon ( Oncorhynchus spp. ) recreational fisheries to help balance management objectives of stock conservation and sustainable harvest. Although sustainability is contingent upon low post-release mortality, CR post-release mortality in marine recreational salmon fisheries has rarely been estimated and the underlying mechanisms are not well understood. We angled Chinook salmon ( O. tshawytscha) using approaches typical for the fishery, then transported fish to ocean-side tanks for 10-day observations. Angling treatments included hook type (barbless; single vs. treble), lure type (bait vs. artificial), in-line flasher use (yes vs. no), and release approach (gaff-release vs. no gaff-release). Treble hooks were associated with poor survival in small fish (37 % survival for fish < 60 cm). Immediate mortality (< 2 h after capture) occurred in 8.4 % of Chinook salmon, and was associated with bleeding, sea surface temperature, fork length, transfer time, and the inner mouth hook location. There was little mortality until day-3, then mortality increased to day-5, and was associated with high levels of bleeding, fin damage, vessel transfer, scale loss, fork length, gill impairment, and sex. Fish with minor injuries had 74 % higher survival to the end of the holding period than those with high levels of bleeding, scale loss, and fin damage. Post-release mortality of Chinook salmon in the marine recreational fishery can be minimized through improved fish handling and release practices, specifically by not using treble hooks, avoiding small fish, and releasing fish at the water line without the use of a net. • Injury severity was associated with immediate and delayed mortality. • There was little delayed mortality until days 3–5 during 10-day observations. • Treble hooks caused severe wounds and high mortality in small fish. • Releasing fish at the water line avoids net-use, reduces injury risk and delayed mortality. • We provide gear and angler practices that enhance the survival of released Chinook salmon.