Catch and Release in Marine Recreational Fisheries

Hook-and-Release Mortality of Chinook Salmon from Drift Mooching with Circle Hooks: Management Implications for California’s Ocean Sport Fishery

A. M. Grover, M. S. Mohr, and M. L. Palmer-Zwahlen

doi: https://doi.org/10.47886/9781888569308.ch6

Abstract.—A total of 276 chinook salmon Oncorhynchus tshawytscha, less than 660-mm total length, were drift mooch-caught using barbless circle hooks and held for four days in 8,700 L, onboard holding tanks for wound location-specific, mortality rate evaluation. Only gut-hooked fish died in the first 24 hours of holding, and only lower-jaw hooked and gut-hooked fish died within the first 48 hours of holding. Gut-hooked fish that survived the four day holding period but whose internal organs were severely damaged were considered mortalities. The four day mortality rate attributable to the effects of handling and holding alone was estimated to be 0.048, based on a surrogate control group consisting of tank-held fish having no wounds or superficial wounds. The controladjusted, four day mortality rates depended strongly on hook wound location. The distribution of wound locations in the California recreational drift mooch salmon fishery was estimated based on a sample of 522 fish, less than 660-mm total length; the relative frequency of gut-hooked fish (0.406) was twice that of any other location. The fishery overall hook-and-release mortality rate was estimated to be 0.422 (95% confidence interval of 0.342–0.502), obtained by weighting the wound location-specific, four day mortality rates by the relative frequency of those wound locations in the fishery. The distribution of wound locations was found to depend on both hook size and fish-size class, but the effects of these factors were not additive on the log-odds scale. Blood plasma cortisol concentration, a measure of stress, was significantly higher in fish held for four days than in ocean-caught (presumably stress-free) fish, but there was considerable variation among individuals and the results were not useful in evaluating the effects of wound-induced stress. The requirement that (only) barbless circle hooks be used in the California drift mooch fishery substantially reduced the hook-and-release mortality rate in this fishery; however, the rate is still high. Hook-and-release mortality might be reduced further by educating anglers on the use of drift mooch methods that lessen the probability of gut hooking. If such education is effective in changing the fishery’s wound location profile, our estimate of the hook-and-release mortality rate can be easily updated using the methods described in this paper.