Quantifying entanglement risk reduction to North Atlantic right whales from time-area closures in the southern Gulf of St. Lawrence snow crab fisheries

Time-area closures for non-tended, fixed-gear fisheries have been implemented in Atlantic Canada since 2018 as a protective measure for North Atlantic right whales Eubalaena glacialis (hereafter, ‘right whales’). The protocols for triggering closures have changed in each subsequent year without quantitative estimates of their effectiveness to mitigate entanglement risk. Using a counterfactual approach, we conducted an evaluation of 4 closure protocols (2018-2021) for reducing entanglement risk to right whales in the southern Gulf of St. Lawrence (GSL) snow crab fisheries to determine: (1) the effectiveness of each annual closure protocol and (2) the estimated entanglement risk removed each year. Co-occurrence of fishing gear and whales was used to estimate the monthly baseline entanglement risk and assess the amount of risk removed by the time-area fishery closures. Risk reduction considered rate of gear removal, amount of gear lost and reintroduction of risk due to redistributed fishing effort. Effectiveness of each protocol was assessed by creating closure scenarios from each annual whale detection pattern (2018-2021). Protocols from 2018 and 2019 showed larger risk reductions in some months than those from 2020 and 2021, but annual reductions in entanglement risk did not differ significantly. Over these 4 years, annual entanglement risk to right whales from the GSL snow crab fishery is estimated to have been reduced by approximately 62 ± 3% (mean ± SE) relative to pre-closure estimates of risk. This study represents the first effort to quantify the Canadian fisheries management measures towards North Atlantic right whale protection, having utility to improve conservation management efforts.