Estimating mortality of Atlantic bluefin tuna ( Thunnus thynnus) in an experimental recreational catch-and-release fishery

Abstract

The abundance of Atlantic bluefin tuna has been severely reduced since the advent of industrial fishing. A recreational catch-and-release fishery is currently being developed to target bluefin tuna in the southern Gulf of St. Lawrence, off the coast of Prince Edward Island, Canada. To evaluate the sustainability of this fishery, it is necessary to quantify post-release mortality for use in management models. Using pop-up archival satellite tags, we estimated the post-release mortality rate of bluefin tuna captured and released in an experimental recreational fishery. Fish were captured using bait on circle hooks and all fish were hooked in the jaw. Fish were released without being brought onboard the boat. Tags reported from 2 to 246 days post release. Two of 59 bluefin tuna died after catch-and-release yielding a mortality rate of 3.4% (95% C.I. = 0.8% < u < 12.6%). Four tags failed to report. Alternate estimates of the rate or mortality that included an incidental mortality (5.1%; 95% C.I. = 1.6% < u < 14.4%) and removal of the four tags that did not report from the sample (5.6%; 95% C.I. = 1.8% < u < 15.6%) were calculated. The range of fight times was 6–79 min (mean of 33 min; SD of 21 min). These data provide the first mortality estimates for angled and released bluefin tuna and will enable managers to evaluate the potential for developing a catch-and-release fishery in the southern Gulf of St. Lawrence.