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

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 similar to 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.