Human Impact on the Twenty-Four-Hour Patterns of Steller Sea Lions' Use of a Haulout in Hokkaido, Japan.

Steller sea lions (SSLs) migrate to the Hokkaido coast to spend the winter there, leading to conflicts arising with fishermen over herring. This study analyzed the trends in the SSLs' use of a haulout as a rest site under human pressure. From January to March in 2017, 2018, and 2019, we recorded the SSL behavior at the haulout site off Otaru City, Hokkaido, for 24 h a day using a fixed-point video recorder. We investigated three years of data to analyze the relationships between the SSL behaviors (attendance/landing-entry timings/remaining on land) and herring caught. We also monitored the SSL behaviors during changes in weather conditions and under human pressure. Throughout the three years, the SSLs used the haulout site during harsher weather or under human pressure. In 2017 and 2018, there was a correlation between the herring caught and the maximum number of SSLs on the haulout, but not in 2019. The number of SSLs on the haulout increased from evening to night; most individuals entered the water in the morning. The SSLs probably return to the water around sunrise not only for foraging but also to avoid anthropogenic pressure. The damage caused to the herring fishery by the SSLs was severe, but it is also clear that human pressure changed their behavior in response.

Survey of ophthalmic disorders among captive pinnipeds in Japan.

Pinnipeds have evolved enlarged ocular bulbs to catch fish in the dark. However, their large protruding eyes are easily damaged, which increases the risk of blindness and death in these animals. In captivity, ophthalmic disorders, manifested as keratitis and cataracts, are common among pinnipeds. In this study, we investigated symptoms of ophthalmic disorders in pinniped species using a questionnaire distributed to 32 zoos and aquariums throughout Japan. We conducted this study in cooperation with the Japanese Association of Zoos and Aquariums. The survey included 295 pinnipeds from four otariid species, five phocid species, and one odobenid species. Of these, 43.1% of the pinnipeds had diseases affecting the lens, cornea, and/or other eye parts. Age was positively associated with lens disorders in California sea lions, South American sea lions, and spotted seals. Conflicts and public appearances were also associated with corneal and/or lens disorders in California sea lions. Treatments were evaluated as effective for corneal disorders and conjunctivitis. The results of this study indicate that ophthalmic disorders in pinnipeds are related to the conditions of their captive environment. Aquariums and zoos should be encouraged to share information regarding optimal maintenance practices to improve the living conditions of pinnipeds.

Comparison of serum lipid compositions, lipid peroxide, alpha-tocopherol and lipoproteins in captive marine mammals (bottlenose dolphins, spotted seals and West Indian manatees) and terrestrial mammals.

Concentrations of serum lipid components, lipid peroxide (LPO) and alpha-tocopherol and electrophoretic patterns of lipoproteins in serum samples obtained from captive marine mammals and terrestrial mammals were compared. Serum concentrations of total cholesterol, free fatty acid, and phospholipid in fish-eating animals were significantly higher than those in manatees and cows. Serum LPO and alpha-tocopherol concentrations in the fish-eating animals were also significantly higher than those in manatees, cows and dogs. Different patterns of densitometric scans of low density lipoprotein (LDL) and a significantly lower percentage of LDL were demonstrated in the dolphins compared with the seals, cow and dogs. The concentration of LPO was significantly correlated with triglyceride and phospholipid concentrations in serum from the dolphins. These results suggest that triglyceride and phospholipid are susceptible to oxidative reaction in fish-eating animals. Evaluation of serum lipids, LPO and alpha-tocopherol concentrations is needed for nutritional husbandry for fish-eating animals.