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

Abstract

Empirical discard mortality rate estimates are vital to both stock assessments and fishery management, especially for stocks that experience high discard rates, such as in the recreational rod‐and‐reel fishery for Haddock Melanogrammus aeglefinus in the Gulf of Maine. The objective of the present study was to derive a fishery‐scale discard mortality rate estimate for Haddock that are captured and released in the Gulf of Maine recreational fishery by combining results of an electronic‐tagging telemetry experiment with representative fishery‐dependent survey data. Scientific personnel and industry partners collected data on a suite of biological, environmental, and technical covariates from 2,442 Haddock caught under authentic fishery scenarios during 2015. Despite being a physoclistous species, <1% of sampled Haddock were observed to die when brought onboard and only ~3% floated upon release. Postrelease fate was then monitored for 154 Haddock using passive acoustic telemetry and determined using a semiquantitative classification procedure reliant upon movement data of Haddock with known fates. The resulting data were analyzed with a parametric survival model to identify which capture‐related covariates influenced mortality. Fishing season and length‐class of Haddock were the most significant predictors of discard mortality, with increased mortality for smaller individuals caught during the autumn, possibly due to increased temperatures. Survival modeling identified that mortality from these covariates occurred primarily after release as compared with during capture and handling. By integrating survival modeling results with fishery‐dependent observations, a fishery‐scale discard mortality rate of 63% was estimated for the 2015 fishing year. Based on these findings, we recommend that fishery managers implement measures to reduce recreational Haddock discards, especially of smaller Haddock during warmer months.

Estimating the Discard Mortality of Atlantic Cod in the Southern Gulf of Maine Commercial Lobster Fishery

“…to the mortality of a species can be used to recommend best fishing practices within a given fishery. For example, previous research regarding best practices for gadoids in the recreational rod‐and‐reel fishery offered suggestions to avoid fishing grounds with smaller individuals (Capizzano et al 2019) and to minimize handling times (Capizzano et al 2016) so as to reduce injury and mortality. Interestingly, the current study found no significant predictors of AVM.…”

“…For example, soak time may not accurately reflect the amount of time individuals were confined in lobster traps, as fish have been observed to enter and exit trap gears at will (i.e., Jury et al 2001; Cole et al 2004). It is also important to consider the likelihood of additional stressors that were unaccounted for in our survival model (i.e., air exposure duration, fish size, and catch biomass) and that have been found to be related to mortality in other species (i.e., Capizzano et al 2016, 2019). Given these uncertainties, further research into the specific factors contributing to the mortality of Atlantic Cod captured in the GOM commercial lobster fishery is needed in order to provide recommendations for best fishing practices.…”

Untitled

“…Results of recent studies indicate that discard mortality rates in recreational fisheries are influenced by numerous biological, environmental, and technical factors (e.g., Capizzano et al, 2016Capizzano et al, , 2019Weltersbach et al, 2019). Therefore, fishery-or region-specific estimates of discard mortality and recommendations for anglers for best practices in catch and release of black sea bass are required to provide the information needed for stock assessments, fishery management, and conservation efforts.…”

“…Step 2 included the application of a variance test on depth observations recorded at defined intervals throughout the detection history of each acoustically tagged fish (Capizzano et al, 2016(Capizzano et al, , 2019. Only intervals with at least observations were included in the analysis.…”

Assigning Fates in Telemetry Studies Using Hidden Markov Models: an Application to Deepwater Groupers Released with Descender Devices

“…The behavior of these transmitters attached to known‐dead fish can then be scrutinized, and any similar patterns among fish released alive imply discard mortalities (Yergey et al 2012; Capizzano et al 2016; Zemeckis et al 2020). A more opportunistic approach to identifying fate involves resighting or recapturing a live, tagged animal after a period at large, thereby confirming that all data between release and recapture were generated by that individual and allowing for comparisons as above (i.e., a positive control; Capizzano et al 2019). Even with these approaches, comparing the detection information of individuals with known and unknown fates is typically at best a semi‐quantitative procedure (Benoît et al 2012).…”