An Estimate of Postrelease Mortality of School-Size Bluefin Tuna in the U.S. Recreational Troll Fishery

The recreational fishery for juvenile Bluefin Tuna Thunnus thynnus along the U. S. Atlantic coast has a large number of regulatory discards, but little information exists on the fate of released fish. We deployed 20 pop-up satellite archival tags programmed to release after 31 d to estimate the postrelease mortality of school-size (69-119 cm curved FL) Bluefin Tuna caught in the recreational troll fishery. All fish were captured using lures or lure-bait combinations rigged with standard J hooks. Nineteen of the 20 tags (95%) reported, and analysis of temperature, depth, and light data indicated that all 19 fish survived for the tagging period. Three tags released prematurely (after 6, 7, and 26 d), and we inferred that one individual was consumed by a shark after 12 d. However, all four of these fish displayed behavior indicative of survival until the tag either released or the fish was consumed. Although the power of this analysis is limited by the relatively small sample size, the observed postrelease mortality rate of 0% suggests that the recreational catch-and-release troll fishery for school-size Bluefin Tuna does not represent a significant source of fishing mortality.