Analysis of commercial hunting on northern fur seal ( Callorhinus ursinus) at Tyuleny Island

Abstract

Structure of commercial hunting on northern fur seal at Tyuleny Island is considered including effectiveness of podding, age-sex composition of the podded and captured animals, age structure of culled males, and reasons of culling. In total, the number from 2650 to 5099 of fur seals were podded during the harvest seasons of 1990-2008, 45.80 ± 2.17 % of them were killed and 54.20 ± 2.16 % were released. The bachelors prevailed among the podded animals, as well as in the bachelor rookeries (51.70 ± 2.56 %). The bulls were more numerous in the pod (35.80 ± 2.12 %) in compare with the half-bulls (10.20 ± 0.99 %) and the females (2.00 ± 0.85 %). Among the harvested animals, the bachelors prevailed, as well (93.50 ± 1.06 %), whereas the bulls, females, and half-bulls weren’t numerous (3.83 ± 0.87 %, 2.51 ± 0.67 %, 1.49 ± 0.29 %, respectively); frequency of the bulls and females captures changed from year to year. The most numerous age group of captured seals was the 3-year old animals (52.80 ± 1.60 %). All groups were presented among the culling animals, but the bachelors prevailed. The most common reason for culling was injuring of seals by commercial fishery wastes (scraps of fishing nets, ropes, packaging tapes, etc.): 64.20 ± 6.86 % of the culled animals were injured by the wastes.