Expected mortality risk for coho salmon landed in recreational troll fisheries using 1/0 and 6/0 hooks in the marine waters of Washington state

Recreational salmon fisheries in the state of Washington are managed with size-selective and mark-selective rules to promote the release of wild and undersized salmon. In order for this management approach to be effective, the fishery must have low mortality of hooked and released salmon. In this study, we directly compared the fishing performance of small (1/0, 14.36 mm gap) and large (6/0, 17.20 mm gap) hooks in recreational salmon troll fisheries with the goal of evaluating differences in drop-off rates, size of salmon caught, and the probability a fish would be hooked in a region documented to have low, intermediary, or high risk of mortality. We found strong evidence that hook size affects the probability that an angler can land a fish with drop-off rates of 48.9% for fish hooked on small (1/0) hooks and 34.0% for fish hooked on large (6/0) hooks. There were no significant differences in the average length of pink, coho, or Chinook salmon caught on small (1/0) or large (6/0) hooks. Likewise, we found no significant differences in the proportion of coho and Chinook catch that were longer or shorter than their respective legal-size limits. Hook size did significantly affect the expected mortality risk of coho salmon with large (6/0) hooks being 1.82 times more likely to hook a salmon in body regions associated with high or intermediary risk of mortality than small (1/0) hooks. No significant differences were observed in the hooking rates of Chinook and pink salmon in body regions with high, intermediary, or low expected mortality risk, however our confidence in this finding is limited due to sample size. It is important to carefully assess whether these results support restrictions on hook sizes used in recreational coho salmon troll fisheries. The observation of reduced expected mortality risk of coho salmon landed using small (1/0) hooks as compared to when using large (6/0) hooks highlights the importance of evaluating the effect of hook size during recreational salmon troll fisheries on post-release survival and will hopefully stimulate more research on the effects of hook size and modeling on whether hook size regulations can improve salmon conservation.