Abstract
The current level of annual incidental bycatch of gray seals Halichoerus grypus in the New England sink gillnet fishery is the highest for all marine mammal species in the USA. One way to evaluate the risk of bycatch is to examine the risk of encounter between an animal and fishing gear based on the animal’s habitat use in relation to fishing activity. Here we used satellite telemetry deployed on 30 gray seal pups in 2019 and 2020 to measure the risk of encounter with large-mesh sink gillnet fishing effort throughout the Gulf of Maine and southern New England. We estimated relative encounter risk within 30 min grid cells in each calendar quarter based on the overlap of seal presence and fishing effort, and then validated the expected risk based on bycatch events reported by independent observers on board fishing vessels. The relative risk of seals encountering gillnet fishing gear was highest off southeastern Massachusetts in spring. Patterns in the estimated encounter risk fit our expectation that relatively high levels of habitat use and fishing effort correspond to increased encounter risk. The approach taken here can be used to identify times and areas of high encounter risk to justify altered fishing practices for purposes of avoidance, or to target observer monitoring intended to characterize and quantify bycatch. Mitigation strategies will need to be continuously monitored and updated to incorporate new information as conflicts with fisheries and gray seals are likely to continue.
Highlights
As some protected wildlife populations recover or expand throughout their range, conflicts with commercial and recreational fisheries have increased (Larson et al 2013, Cook et al 2015, Cosgrove et al 2016, Olsen et al 2018)
Many animals are seen living with serious entanglements that will likely result in a mortality, so actual bycatch may be higher than previously estimated (Martins et al 2019)
This study showed a significant pattern of spatial overlap between young-of-the-year gray seals and sink gillnet fishing effort in the northeast and MidAtlantic regions of the USA
Summary
As some protected wildlife populations recover or expand throughout their range, conflicts with commercial and recreational fisheries have increased (Larson et al 2013, Cook et al 2015, Cosgrove et al 2016, Olsen et al 2018). Animals may prey upon target catch (Rafferty et al 2012, Peterson & Carothers 2013, Cosgrove et al 2015), and damage or become entangled in fishing gear (Kauppinen et al 2005, Moore et al 2009). These direct interactions can incur significant economic costs to fishermen Solutions are needed to reduce bycatch to spare fishermen from unnecessary gear damage and potential economic losses This would confer animal welfare benefits and help minimize resources spent on responding to stranded and entangled animals
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