野生生物と社会
Online ISSN : 2424-2365
Print ISSN : 2424-0877
ISSN-L : 2424-0877
4 巻 , 2 号
選択された号の論文の5件中1~5を表示しています
原著
  • 羽根田 貴行, 諸星 綾, 小林 万里
    2017 年 4 巻 2 号 p. 1-10
    発行日: 2017年
    公開日: 2017/06/17
    ジャーナル フリー

     The Pacific Ocean along the coast of eastern Hokkaido is rich in marine resources and many pinniped species inhabit the area. In this study, we report the pinniped numbers and species that are incidentally caught in salmon set nets in the waters off eastern Hokkaido from spring to autumn in 2012-2014.

     As a result, the number of by-catch individuals was higher in spring than in autumn, with the majority of animals caught in Konbumori and Hamanaka, respectively. Individuals of all the pinniped species that inhabit the Hokkaido coast were caught in spring. The main seal species caught in this season were harbor seals, spotted seals, and northern fur seals, whereas the majority of by-catch animals in autumn were harbor seals. Most of the by-catch seals were young individuals. However, in addition to pups, pregnant northern fur seal females were caught incidentally, likely while moving northward to breed. Migratory pinnipeds depends on the environment, the change in the number of by-catch by year was great. In contrast, resident species changed little.

     Therefore, status of the by-catch of migratory pinnipeds can be used as an indicator of environmental changes, whereas, the current inhabitant changes for resident species such as harbor seals.

  • 後藤 直子, 竹下 和貴, 丸山 哲也, 梶 光一
    2017 年 4 巻 2 号 p. 11-18
    発行日: 2017年
    公開日: 2017/06/17
    ジャーナル フリー

     Hunting statistics provide valuable information for planning and conducting appropriate ungulate management. We compared the age- and adult sex-ratios of three wild boar sub-populations under three hunting methods (box trap, snare trap, and gun) using hunting statistics collected by Tochigi prefecture between FY1997 and FY2013. These sub-populations are genetically distinct, and differed in each distributed period. In all regions, the ratios of adult wild boar hunted by gun and captured by snare trap were higher than that by box trap. Furthermore, in all regions, there were no differences in adult sex ratios among all hunting methods. Selective hunting techniques for adult wild boar might exist in gun and snare trap hunting. An analysis of hunting methods using long-term hunting statistics is necessary for future wild boar management with limited funds and hunting effort.

報告
  • 増渕 隆仁, 大山 奈緒子, 相崎 翔, 岡田 華奈, 大野 慧, 石川 昭, 越後 啓之, 鈴木 公一, 駿河 秀雄, 小林 万里
    2017 年 4 巻 2 号 p. 19-27
    発行日: 2017年
    公開日: 2017/06/17
    ジャーナル フリー

     In the 1970s, about 50 Kuril harbor seals (Phoca vitulina stejnegeri) were observed hauling out in Cape Erimo, Hokkaido, Japan. However, the number increased to approximately 600 individuals in the 2000s, which was 12 times the number recorded previously. Consequently, damage to the fish catch in the salmon fixed nets also increased and has become a serious problem. However, very few quantitative assessment reports have been published about the 70 incidents of damage to fish catches.

     In this study, we tracked the seals using acoustic telemetry in order to understand their behavior around the nets, and we also carried out a questionnaire survey to ascertain the number of salmon that were damaged by seals and the behavior of the 75 incidental seals caught in the nets between 2012 and 2015.

     The results indicated a large number of seals stayed around set net “M,” which is the closest net to the haul-out site (located about 3 km east of the site). They visited the site frequently and for long periods of time. The proportion of salmon bitten by seals was also large in the “M” net, and the percentage has risen every year. Furthermore, the number of seals caught (85) was also high in net “M.”

     This study investigated the damage to the salmon fishery fixed equipment caused by Kuril harbor seals in Japan by evaluating seal behavior and by undertaking a questionnaire survey.

  • 松田 春菜, 田代 優秋
    2017 年 4 巻 2 号 p. 29-37
    発行日: 2017年
    公開日: 2017/06/17
    ジャーナル フリー

     In order to convey information on new endemic species, a scientist gave a lecture to elementary school children. In the study, the additional effects of the lecture on the local community were assessed through a questionnaire, which was administered to the children's guardians. In the lecture, the characteristics of the species and molluscan fauna in the region were described. According to the results of the questionnaire, close to 90% of guardians heard about the lecture from the children, which is higher than the recognition gained from news reports about the findings on the species. The children positively informed their guardians of the visual characteristics they had observed, which were not limited to details presented in the lecture. The guardians' impressions were categorized into four types: (1) the impression of the species, (2) thoughts on their children; (3) wishes, such as for others to know about the species, and (4) motives to gain a better understanding of the species. The multiple choices showed that the last category had a general trend, indicating that when a scientist explains a species for children, the guardians might perceive it as valuable through the children. In addition, nearly half of the guardians said they talked about the species to others afterward. The lecture is considered to be effective for producing a relationship between local residents and endemic species.

  • 角田 裕志, 和田 敏, 安藤 正規
    2017 年 4 巻 2 号 p. 39-46
    発行日: 2017年
    公開日: 2017/06/17
    ジャーナル フリー

     It is concerned that intensive browsing by sika deer (Cervus nippon) has caused declines and disappearances of vegetations in forest floor, resulting in degradations of forest ecosystems across Japan. To determine the effects of deer browsing on forest ecosystems in Gifu Prefecture, we surveyed the decline of understory vegetation in deciduous hardwood forests in 376 forest stands using the shrub-layer decline rank (SDR), which was assessed by combining the coverage of the shrub-layer vegetation and the presence of signs of browsing by sika deer in each forest stand. We found that remarkable declines of vegetations (i.e., shrub-layer vegetation coverage was less than 38%) due to deer browsing were observed in 31.1% of the surveyed stands. We then estimated the spatial distribution of SDR in deciduous hardwood forests, based on sampled data, using a spatial interpolation method in the Geographic Information System. The results of the spatial estimation indicated that remarkable vegetation declines due to deer browsing could be occurred in 22.2% of the forests (1,133.5 km2), mainly distributed western and central areas of the prefecture. Moreover, our findings indicated that effects of deer browsing on forest ecosystem have started to expand northward and eastward of the prefecture. For conservation of forest ecosystem, we suggest reinforcing sika deer culling in the northern and eastern areas of Gifu Prefecture, where numbers of deer caught were relatively smaller than those in the western and central areas.

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