Evaluating the effects of North Atlantic right whale (Eubalaena glacialis) fishery closures on entanglement risk of other large whales from the southern Gulf of St. Lawrence snow crab (Chionoecetes opilio) fishery

Abstract

Since 2018, time-area closures have been implemented in Atlantic Canada to reduce entanglements of North Atlantic right whales (NARW) in fixed-gear fisheries, particularly the Gulf of St. Lawrence (GoSL) snow crab fishery. Other large baleen whale species also occur in GoSL and face similar risks of entanglement. These include endangered blue whales, fin whales (special concern), and humpback whales, the second most commonly entangled baleen whale in Atlantic Canada, and other studies have shown the rate of entanglement for these whales in the GoSL are vastly underestimated. The goal of this study was to estimate the risk of entanglement in snow crab gear for these other species, and to quantitatively evaluate the potential change in risk due to the NARW time-area closures. Distributions for each species were based on annual sightings (2015-2022) using a location uncertainty model and combined with snow crab logbook data to estimate entanglement risk. The average risk of entanglement for blue, fin, and humpback whales was estimated for the years prior to the implementation of fisheries management measures (2015-2017) and compared to the entanglement risk estimate for each year with time area closures (2018-2022) to identify the change. The results showed ranges in annual change in risk of -50.76 to -9.04% for blue whales, -70.70 to 6.21% for fin whales, -73.51 to 34.56% for humpback whales, where negative values indicate a decrease. Monthly results show some risk reduction from certain management measures, but an increase as an unintended consequence from others. This study provides important information on the effects of fisheries management measures on non-target whale species.