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To understand the current feeding habits of spotted seals, this study estimates feeding strategies based on region, season, growth stage, and sex through the results of stomach content analyses, and compares its findings with feeding habits of the past. As a result of permutational multivariate analysis of variance (PERMANOVA), region, season, growth stage, and sex were detected as significant. Non‐metric multidimensional scaling (nMDS), hierarchical cluster analysis, and the growth stages were categorized into age classes: Age 0 to age 4 years were classified as young, and age 5 and older were classified as adult. For the seasons, November and December were classified as winter, and February to May was classified as spring. And clustering with flexible mixture modeling, samples were divided into eight feeding strategies. In Rebun, the feeding strategy consisting of Octopodidae species showed a high total energy value and appeared at a high occurrence rate for both young and adult. In Saroma, Osmeridae species in winter and Clupeidae species in spring showed a high proportion. Both Osmeridae and Clupeidae species showed a high proportion in both seasons, all growth stages, and both sexes. In Rausu, adult was particularly dominant in Alaska pollock (Gadus chalcogramma) in spring, while young appeared at a high rate in Ammodytidae species. The present study has shown that seals have become particularly dependent on fish in all layers of the marine environment. In addition to drastic changes in their environment, the increase in the number of individuals of a competing species that is Steller sea lions in Rebun, and a decrease in fishery resources have made it impossible for spotted seals to take advantage of their high‐energy feeding strategy mainly composed of Alaska pollock both Rebun and Rausu. As a result, regional differences in feeding strategies for both Rebun and Rausu have become more clearly differentiated than in the past, and the seals have flexibly changed their feeding strategies to accommodate the availability of prey species in their particular region. This study has succeeded in accurately classifying the feeding strategies of spotted seals in three disparate regions of Hokkaido and has revealed significant temporal and regional differences. [ABSTRACT FROM AUTHOR]

Abstract--The population structure and abundance of the American lobster (Homarus americanus) stock in the Gulf of Maine are defined by data derived from a fishery-independent trawl survey program conducted by [...]

Pacific bluefin tuna ( Thunnus orientalis) migrate to the south-western North Pacific spawning grounds (area off Taiwan and the Ryukyu Islands) from mid-April to early July. Reproductive traits of the species in this area have been studied for some time; however, temporal changes in spawning activity during this season are not well understood. In this study, the spawning fraction (proportion of females with post-ovulatory follicles to total mature females) in relation to solar calendar date and lunar day was investigated using a generalized linear model. Sampling was conducted almost every day throughout the fishing season at Ishigaki Fishing Port (24°21′N, 124°09′E), southern Japan between 2012 and 2014, and a total of 212 ovaries were histologically observed. Spawning fraction continued to increase from the beginning to the end of the season. This indicates that the peak season of occurrence in the area and the peak of spawning activity did not co-occur. Spawning fraction also changed with the lunar day and significantly increased around the new moon. Eggs and early larvae hatched around the new moon may have reduced the predation risk during night-time. These findings improve the current knowledge of reproductive biology and resource evaluation of Pacific bluefin tuna and indicate that spawning activity is not constant, and has two or three peaks in each season. [ABSTRACT FROM AUTHOR]

The North Pacific spiny dogfish (SPD), Squalus suckleyi, is a commercially exploited shark species that plays an important role in the ecosystem. To elucidate the distribution of the SPD in the North Pacific and to evaluate the effects of sea surface temperature (SST) and prey availability on its distribution, we estimated the probability of SPD presence using a generalized additive model with a binomial error distribution from SPD presence/absence data on 14,824 operations in fisheryindependent gillnet surveys between 1972 and 2011. The habitat model was structured in the east and west to reflect differences in the North Pacific oceanic environments. In the east, a higher probability of SPD presence was identified along the coast from the eastern Gulf of Alaska to Queen Charlotte Sound. In the west, it was identified around northern Japan. The estimated distribution was continuous between the two areas, whereas the probability of SPD presence was relatively low. Although the probability of SPD presence was higher at SSTs between 6°C and 12°C, the SST at the peak probability of SPD presence differed between the west and east. The prey species, Japanese sardine, Sardinops melanostictus, and walleye pollock, Gadus chalcogrammus, in the west and boreal clubhook squid, Onychoteuthis borealijaponica, in the east significantly affected the probability of SPD presence, which was higher if the prey species co-existed with SPD. Therefore, SPD might adapt their distribution to that of available prey species. SPD stock assessment and management in these two important areas are required for its sustainable utilization. [ABSTRACT FROM AUTHOR]