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

Abstract

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 = 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 = 136) was also tagged with pressure-sensing acoustic transmitters before being released into an acoustic receiver array (n = 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.