The effect of circle hook size on reef fish catch rates, species composition, and selectivity was tested in the northern Gulf of Mexico recreational fishery. Fish communities first were sampled at natural (n = 19) and artificial (n = 23) reefs with a micro remotely operated
vehicle (ROV) equipped with a laser scale. Fishing experiments (n = 69) then were conducted with 9/0, 12/0, and 15/0 circle hooks. Hook size significantly affected fish catch rates, species composition, and size. Small invertivore fishes constituted 33.4% of the catch taken with 9/0
hooks, but were nearly absent from the catch made with larger hook sizes. In contrast, red snapper, Lutjanus campechanus (Poey, 1860), constituted only 25.3% of fishery species total abundance in video samples, but ranged from 59.1% of the 9/0 hook catch to nearly 90% for 15/0 hooks.
A novel maximum likelihood approach was developed to estimate exponential-logistic selectivity functions for each hook size from ROV-based estimates of red snapper size distributions and observed hook-specific catch at size. Both the 9/0 and 12/0 hooks displayed dome-shaped selectivity functions,
while the 15/0 hook size was estimated to have a logistic-shaped function. However, observed catch-at-size data displayed a dome-shaped pattern for 15/0 catches when paired with 9/0 hooks, but an indistinct pattern when paired with 12/0 hooks. Overall, study results suggest that regulating
circle hook size would affect reef fish catch rates and size in the northern Gulf of Mexico recreational fishery, but potential conservation benefits may be confounded by unintended effects.
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