Incidental mortality of seabirds in pollock trawl fishery in the northwestern part of the Bering Sea

Abstract

Purpose of the work: Estimation of average annual number of seabirds that die as a result of lethal strikes with fishing gear in the specialized pollock trawl fishery by large-tonnage fleet in the West Bering Sea zone.Methods used: The article is based on materials collected by ornithologists on large freezer trawlers in the summer and autumn periods in 2020 and 2021. To record bird deaths we used inspection of warps, net sonar wire third cable, net trawl, codend during trawl retrieval and count of bird lethal collisions with fishing gear during observation sessions at all stages of fishing operations. The total mortality was estimated by extrapolating the mean catch-rates (number of dead birds per vessel day) to fishing efforts of large-tonnage fleet in the West Bering Sea zone in 2020 and 2021.Novelty: The annual average mortality of birds in large-scale trawling was determined for the first time for domestic fisheries and an expert assessment of its potential risk to populations of the catched species was carried outResults: The death of 203 birds was recorded during 139 vessel days. The total estimated mortality in fishing gear was 8,355 (CI 5259–11451) birds per year: 4,717 northern fulmars, 1,667 short-tailed shearwaters, 1,006 Laysan albatrosses, 822 black-legged kittiwakes, 48 slaty-backed gulls, 48 Vega gulls, and 47 red-legged kittiwakes. Comparison of these estimates with the global or regional number of birds suggests that mortality in fishing gear in 2020 and 2021 did not have a significant negative impact on the state of species (proportion of dead birds was 0.005–0.085% of their population estimates). Despite the regular presence of short-tailed albatrosses near trawlers in the Navarin area, no deaths in fishing gear were recorded.Practical significance: The results are necessary for the process of ecological certification of the specialized pollock trawl fishery in the West Bering Sea zone.