Biosphere conservation : for nature, wildlife, and humans
Online ISSN : 2433-1260
Print ISSN : 1344-6797
1 巻 , 1 号
選択された号の論文の8件中1~8を表示しています
Reviews & Essays
  • Kazuo Wada
    原稿種別: Reviews & Essays
    1998 年 1 巻 1 号 p. 1-6
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    Steller sea lions (Eumetopias jubatus) occur around Hokkaido Island, Japan, and are mixing there with migratory groups came from the Kuril Islands and small islands around Sakhalin Island during October through May and numerous studies have been published on their ecology while in Japanese waters. While the sea lions are in Japanese coastal waters they commonly inflict serious damage to local fisheries, and since 1961, the Hokkaido regional government financially supported their removal to lessen the damage to fisheries. Total number, 22, 481 of the animals were eliminated around Hokkaido, and were main reason for drastic decline of the Kuril Islands population from 20, 000 in the 1960s to 4, 000 in the 1990s. This animal elimination did not contribute to lessen fisheries damage because a conflict between fisheries and the animal feeding came from over-fishing of fisheries resources. The world-wide Steller sea lion population is declining rapidly, resulting in Russia and the United States implementing numerous legal regulations for their conservation. In this review, I discuss the damage to fisheries caused by Steller sea lions in Japan and then introduce some conservation efforts for Steller sea lions in Japan.
  • Lowell W. Fritz, Richard C. Ferrero
    原稿種別: Reviews & Essays
    1998 年 1 巻 1 号 p. 7-19
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    Recovery of the Steller sea lion (Eumetopias jubatus) population in Alaska constitutes a significant challenge to resource managers since the cause (s) of the decline remain a mystery. However, a principal symptom of the population, increased juvenile sea lion mortality, appears to be related to changes in food availability. Such changes may be due to natural shifts in fish community composition, anthropogenic factors, or both. Commercial groundfish fishing is the primary annually-occurring human activity in this region that has a high potential for competitive interactions with sea lions. Consequently, it has received considerable management attention in efforts to recover the Steller sea lion population. In 1991-93, trawl exclusion zones were created around sea lion rookeries and some groundfish catch quotas were allocated spatially and temporally to minimize the likelihood of localized depletions of sea lion prey. These initial measures partitioned some fishing effort away from sea lion habitats, but the conservation benefits remain uncertain. In this paper, we explore the various options available to managers for further reducing sea lion-fishery interactions using traditional fisheries management tools. Recent trends in groundfish fishery distribution and information on sea lion distributions and foraging ranges suggest several areas of overlap which could be addressed through modified fishing practices. These could include changes in trawl gear size and reductions in total catches of certain groundfish species, as well as spatial and temporal distribution of groundfish catch tuned to seasonal changes in sea lion distribution and foraging range. These measures, in combination, offer mechanisms to more completely incorporate the results of the past decade's research efforts on Steller sea lions in the existing fisheries management framework.
Original Papers
  • Thomas R. Loughlin, Adolf S. Perlov, Jason D. Baker, Sergei A. Blokhin ...
    原稿種別: Original Papers
    1998 年 1 巻 1 号 p. 21-31
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    Satellite-linked time-depth recorders (SLTDR) were attached to eight adult female Steller sea lions (Eumetopias jubatus) at three islands in the Kuril Islands, Russia, during June 1991. The purpose of the study was to enhance our understanding of adult female Steller sea lion dive characteristics and foraging behavior in Russian waters for comparison to similar studies in Alaska during the breeding season. Mean dive depth was 53m (n=7,143) and mean dive duration was 112 sec (n=7,775). Steller sea lions had trips to sea lasting about 1 day, but some trips lasted up to 4 days. Virtually all dives were in the late afternoon through early morning, and 99.5% of the dives> 100m occurred between 2100-0300 hrs. Most (94%) locations indicated that the sea lions foraged within 10 km of the capture island, but some traveled as far as 263km. Dive depth and duration varied by individual and by island. Five sea lions from Lovushki Island had statistically longer duration (p<0.05) and deeper (p<0.05) dives than three females from Brat Chirpoyev and Raykoke Islands. The Lovushki Island animals also tended to dive in shallower water over a large reef complex suggesting that they foraged near bottom while sea lions from the other two islands foraged near the surface in deep water. The results support the hypothesis that adult female Steller sea lions in the Kuril Islands have dive characteristics similar to Alaska sea lions.
  • Donald G. Calkins
    原稿種別: Original Papers
    1998 年 1 巻 1 号 p. 33-44
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    One hundred and ten Steller sea lions (Eumetopias jubatus) that moved to the seasonal ice edge in the Bering Sea in late winter of 1981 were collected. Stomachs were examined to determine prey. Two areas were studied, one near the Russian coast in Olyutorskiy Gulf and one in US waters in the central Bering sea. Origin of the animals was probably rookeries and haulouts in the Aleutian Islands, the Commander Islands and the east coast of Asia. Only males were present. All age classes from 1 to 16 were taken but no pups of the year. Prey were found in 92 stomachs. Walleye pollock (Theragra chalcogramma) dominated overall, accounting for 67% of prey by weight. The second most important prey was Pacific cod (Gadus macrocephalus) which accounted for 15% by weight. Other important prey were squids and octopus, cephalopods; sculpins, Cottidae; Pacific herring, Clupea herengus; flatfishes, Pleuronectidae; other unidentified bony fishes; and Phocid seals, Phocidae. Pollock consumed by sea lions in the Bering Sea were similar in size to those consumed in the Gulf of Alaska in the 1980s but were smaller than those consumed in the Gulf of Alaska in the 1970's. Larger sea lions ate larger pollock. Pollock were important in the diets of sea lions in numerous other studies in both the Gulf of Alaska and Bering Sea. This is in marked contrast to prey remains found in scats from adult females at rookeries and haulouts during summer from the Aleutian Islands and Gulf of Alaska in 1990-1993. This could simply reflect a real shift in diet from 1981 to the 1990s but is complicated by differences in season, location and sex. Predation on other pinnipeds appears to be common by Steller sea lions.
  • Kenji Konishi, Kenji Shimazaki
    原稿種別: Original Papers
    1998 年 1 巻 1 号 p. 45-48
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    Steller sea lions (Eumetopias jubatus) are infested by many parasites through various routes, including predator-prey relationships and contacts with other sea lions. However, we know little about the life histories of these parasites. This paper discusses a nasal mite (Orthohalarachne attenuata) that infests the respiratory tract of Steller sea lions. Of 22 sea lions sampled around Hokkaido in 1996, the nasal cavities of 12 were infested with the mites. An average of 23 mites were found in each infested sea lion. There was no correlation between the age of the sea lions and the number of mites they contained. The heads of 9 pups were also examined to determine when first infestation occurred. No pups were infested and none had inflamed nasal cavities.
  • Norio Takahashi, Kazuo Wada
    原稿種別: Original Papers
    1998 年 1 巻 1 号 p. 49-62
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    The Steller sea lions, Eumetopias jubatus, in the Kuril Islands, Russia, has declined in number since the early 1960s. One factor which may have caused their decline is hunting in the waters of Hokkaido, Japan. Hunting of sea lions has been conducted during their annual dispersal to Hokkaido in an attempt to reduce damage to local fisheries. In this study, we analyzed the effect of damage control hunting in Hokkaido on the sea lion population of the Kuril Islands from 1958 to 1994 using a demographic model which was developed as an extension of a Leslie matrix. Because a life table had not been calculated for the Kuril Islands population, we assumed that the population followed the vital parameter values estimated by Calkins & Pitcher (1982) and York (1994) for Steller sea lion populations in Alaska, USA. Data on hunted individuals were obtained from regional government records. In our simulation analysis we establish several different scenarios, and also investigate the sensitivity of our results due to uncertain parameters. Where we assumed an absence of hunting, the population was kept constant at 20, 000 sea lions, even when including the effects of environmental stochasticity on the probability of survival and fecundity. In the presence of hunting, the population decreased between 34% and 59% from the 1960s to the 1990s. When we included an effect for incidental catch by trawl vessels in the western Bering Sea and Okhotsk Sea, our analysis predicted a tendency for population declines similar to that which was observed. We conclude that the hunting of sea lions in Hokkaido most likely depleted the population in the Kuril Islands. When other factors such as incidental catch are combined with the pressures of hunting, the decline in sea lion population is even larger.
  • Caitlin B. Angeli, Naoki Maruyama, Masaaki Koganezawa, Masao Takahashi ...
    原稿種別: Original Papers
    1998 年 1 巻 1 号 p. 63-71
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    We conducted a survey on Japanese peoples' attitudes concerning wolves and their reintroduction into Japan during the summer and fall of 1996. The survey was distributed to 2, 000 individuals. Surveys were returned by 1,176 people, 649 females and 508 males ranging from their teens to over 80 years old; a response rate of 58.8%. Twenty-eight point five percent of the respondents supported reintroduction of wolves into Japan, and 27.7% were opposed. The remaining 43.8% were undecided. The main reasons for supporting reintroduction were the beliefs that it is our duty to restore what we once caused to become extinct and that the wolf is essential to restore the balance of Japan's ecosystems. The main reason for not supporting reintroduction was the belief that there is no space in Japan large enough to support a viable wolf population. Securing adequate land was also an important management concern, should wolves be introduced. Compared to the results of the 1993 survey, the percentage of people supporting reintroduction has more than doubled, while the percent of people opposing reintroduction has decreased from 45.0% to 27.7%. Based on crosschecking, a greater percentage of supporters were knowledgeable about the wolf than opponents. In addition, compared with the supporters, a greater percentage of the reintroduction opponents had a negative attitude towards wolves.
  • Kun Shi, Naoki Maruyama, Zhongxin Gao, Masaaki Koganezawa, Jingchun Ji ...
    原稿種別: Original Papers
    1998 年 1 巻 1 号 p. 73-80
    発行日: 1998年
    公開日: 2017/09/07
    ジャーナル フリー
    The impact of settled grazing on the grassland ecosystem of the Nantun Area, northern Inner Mongolia, was surveyed along a 20 km long transect from Holobo Village, with ca. 800 residents, to the east in middle June 1996. Decrease in plant coverage and number of plant species, and shortening of plant height were observed as distance from the village decreased. It was evident that such degradation of vegetation and soil hardening were caused by an increase in the population of humans and livestock, which was promoted by the settlement campaign of 1960. However, recovery of vegetation and soil conditions were observed in mowing lease lands where free-grazing had been prohibited since 1985 during the growing season.
feedback
Top