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59 巻 , 1 号
選択された号の論文の11件中1~11を表示しています
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本論文
  • 大畑 剛史, 乾 隆帝, 中島 淳, 大浦 晴彦, 鬼倉 徳雄
    59 巻 (2012) 1 号 p. 1-9
    公開日: 2013/11/22
    ジャーナル フリー
    Acheilognathus cyanostigma is an exotic fish species in Kyushu Island, being an endangered species in central Honshu Island. The distribution pattern of the exotic population in the Midori River system, Kyushu Island, Japan was examined, the species occurring at 28 low-altitude sites out of 96 sites investigated. The relationships between presence/absence of the species and environmental factors (altitude, water depth, current velocity, turbidity, river width and riverbank conditions) were analyzed using a generalized linear mixed model, riverbank conditions, water depth, turbidity and altitude having either positive or negative effects. In particular, a concrete-covered riverbed was found negatively affect distribution.
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  • 村瀬 敦宣, 宮崎 佑介, 瀬能 宏
    59 巻 (2012) 1 号 p. 11-20
    公開日: 2014/05/16
    ジャーナル フリー
    Twenty-seven individuals of Lateolabrax latus (165.7–691.5 mm in total length), a species normally associated with a rocky offshore habitat in southern Japan, were collected from July to October 2009 in the lower reaches of rivers in Yaku-shima Island, Kagoshima Prefecture, southern Japan by hook and line. Furthermore, schools of immature individuals were observed around hard structures (including rocks and tetrapods) or in riffle zones in the rivers, L. latus clearly making active use of river environments in Yaku-shima Island during its life history. Because a detailed morphological description of the species has not been given since its original description, the specimens from Yakushima Island are described and compared with other congeners. Characters of the former agreed closely with the original diagnosis of L. latus. Some individuals less than 200 mm standard length had tiny scattered spots, smaller than those on other congeners, on the region above the lateral line. Specimens from the Ambo River represent the southernmost record of the species.
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  • 工藤 充弘, 髙津 哲也, 福井 翔太郎, 甲本 亮太
    59 巻 (2012) 1 号 p. 21-35
    公開日: 2014/05/16
    ジャーナル フリー
    Although spawning of Japanese sandfish (Arctoscopus japonicus) does not occur in Mutsu Bay, juveniles of the species were first discovered in the bay in June 2003 (following the initiation of yearly sampling in 1991), also being collected in subsequent years. To better understand the function of Mutsu Bay as a nursery area and the growth characteristics of the early life stages of the sandfish population, their abundance and otolith microstructure were investigated. Juveniles distributed along the sea floor in temperatures of 7.4–10.0˚C were sampled in June 2010, measuring 32.4–62.7 mm in standard length some 100–145 days after hatching, an indication of their having hatched from January 14 to February 27 (24% and 76% of juveniles hatched in January and February, respectively). June sampling surveys, conducted each year, revealed that high juvenile abundance in the bay occurred only when adult sandfish had been abundant in the Sea of Japan, off Akita and Aomori Prefectures. The origin of the juveniles in Mutsu Bay may have been the eastern Sea of Japan population, distributed off the northwestern coast of Honshu Island, the Tsushima/Tsugaru Warm Current possibly conveying the larvae and juveniles into Mutsu Bay. Median hatching dates did not differ between sampling stations in Mutsu Bay, although relatively small juveniles with narrow otolith increment widths occurred in the inner part of the bay in June 2010. Such slow-growing juveniles may have been early arrivals to Mutsu Bay from the hatching area, thereby experiencing colder water in the bay from a young age than later arrivals.
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