Résumé
Grey seals (Halichoerus grypus) feeding on fishery catches, a behavior termed “depredation”, is a major socio-economic and environmental issue in many regions of the north Atlantic. In northern Brittany, seals depredating on monkfish in static nets (gillnet and trammel net) is increasingly reported as problematic, but the issue has yet to be assessed and understood. In this study, we monitored 795 net sets between 2016 and 2018 to i) quantify the frequency of depredation events and the amount of depredated fish and ii) identify the drivers influencing variation in these two metrics. We found that during this period, seal depredation occurred on 18.5% of the net sets and resulted in the removal of 5.3% of the total number of monkfish catches. From statistical models, our results suggested that the probability of seal depredation to occur was higher near haulout sites, in shallower water. However, when depredation occurred, the amount of fish depredated was higher in gillnets than in trammel nets, in longer nets, and nets set further from haulout sites. As seal depredation is likely to escalate with the increase of local grey seal populations, our results provide insights on how fishers may adjust their practices to reduce depredation in northern Britanny and other fisheries facing a similar issue.