Estimating and mitigating the discard mortality of Atlantic cod (Gadus morhua) in the Gulf of Maine recreational rod-and-reel fishery

Abstract

In recent years, the recreational contribution to the total catch of Atlantic cod (Gadus morhua) in the Gulf of Maine (GOM) has increased with recreational discards outnumbering recreational landings by 2:1. However, the discard mortality (DM) rate of cod released in the recreational fishery remains poorly understood, thus contributing to the uncertainty in stock assessments and fishery management plans. The current study examined the capture-related factors most detrimental to cod DM in the GOM recreational rod-and-reel fishery. Atlantic cod (n ¼ 640; 26.0-72.0 cm) were angled from June-October 2013 on southern Jeffreys Ledge in the western GOM using fishing gear representative of the local recreational fishery. A subset (n ¼ 136) was also tagged with pressure-sensing acoustic transmitters before being released into an acoustic receiver array (n ¼ 31) deployed to monitor survival up to 94 days. To properly model DM up to the fishery-wide level, all cod were visually assessed for capture-related injuries according to a four-level injury score index. Mean tackle-specific DM rates of 15.4 and 21.2% were estimated for bait-and jig-captured cod, respectively, with an overall 16.5% mean DM rate for the 2013 GOM recreational cod fishery. Twenty-nine cod tagged with acoustic transmitters were identified as dead, where the majority ( 90%) died within 16 h post-capture. Upon evaluation with a specifically adapted parametric survival analysis, greater incidence of mortality was attributed to the capture and handling process (rather than release) for moderately and severely injured cod. Based on the capture-related factors associated with the highest injury rates, we recommend minimizing fight and handling times, avoiding areas with small cod, educating inexperienced anglers, and favouring bait over jigs to mitigate mortality. Results will continue to inform the development of fishery management plans and enhance survival through dissemination of "best practice" techniques to fishery stakeholders.

Fishery‐Scale Discard Mortality Rate Estimate for Haddock in the Gulf of Maine Recreational Fishery

“…Three terminal tackle types were selected for capturing Haddock due to previous survey results (Table S.1; Capizzano et al. ) and industry input, specifically two baited‐hook setups (J‐ and circle hooks) and one jig and teaser setup (treble‐hook jig) (Figure S.1). Because anglers varied in experience level (as quantified using a questionnaire), efforts were made to remove angling and capture biases that would interfere with the interpretation of study results.…”

“…Equal tackle‐specific fishing effort (i.e., amount of time anglers used bait versus jigs) was also maintained throughout the study to ensure representative samples across angler experience levels, tackle types, and fishing trips (Capizzano et al. ).…”

“…A transmitter retention study was not specifically performed for Haddock, but transmitter loss was considered negligible based on a previous transmitter retention study using this tagging method with Atlantic Cod (100% transmitter retention over 18 d; Capizzano et al. ). All other captured Haddock were externally tagged with two Floy FD‐94 T‐bar anchor tags to opportunistically observe postrelease survival and the movements of recaptures.…”

“…Finally, phase 3 quantified a fishery‐scale discard mortality rate estimate using an extrapolation scheme that capitalized upon the covariate‐dependent discard mortality rate estimates from phase 2 and fishery‐dependent survey data for a subset of recreational Haddock captured in the 2015 Gulf of Maine recreational fishery following the methods of Capizzano et al. (). To determine the uncertainty surrounding this discard mortality rate estimate, we applied a combined empirical and parametric bootstrap routine of 1,000 iterations.…”

Recreational fisheries in the Netherlands: analyses of the 2015 screening survey, the 2014-2015 logbook survey and the 2014-2015 Gillnet survey

“…Because barotrauma was one of the highly significant factors for the mortality of released fish (Bartholomew and Bohnsack, 2005), a 11.2% C&R mortality for cod caught by charter boats in the North Sea is possibly conservative. Capizzano et al (2016) studied the C&R mortality of cod in the Gulf of Maine and found an average mortality rate of 16.5%. We propose the mean between the two studies, resulting in 14%.…”