Fisheries Biology of Blue Sharks in Sagami Bay, Japan
Fisheries Biology of Blue Sharks in Sagami Bay, Japan
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日本相模湾青鲨的渔业生物学
DOI：
10.1007/978-3-030-43484-7_14
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Masao Nemoto
中科院分区：
文献类型：
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作者：
Hiroki Joshima;Chika Namaizawa;Tadashi Miyazaki;D. Shiode;J. Yoshida;Masao Nemoto
蓝鲨(Prionace Gluca)和短鳍黑鲨(Isurus Oxrinchus)是公认的中上层鲨鱼和高度迁徙物种，但这些鲨鱼出现在沿海地区。有人建议鲨鱼在生长阶段迁徙，但我们不知道细节，也不知道鲨鱼如何利用沿海地区。因此，2011年8月至2017年7月，我们在相模湾进行了两种类型的延绳作业，以调查鲨鱼的捕捞趋势：垂直延绳作业和水平延绳作业。这两个物种全年都被捕获，蓝鲨和短鳍黑鲨的高峰期都在7月和12月。许多被捕获的雄性幼年蓝鲨还没有达到性成熟，雌性中也出现了怀孕的蓝鲨。据报道，蓝鲨的产卵期为4月至7月，幼鲨据信在北太平洋的开阔海域出生和长大。然而，我们捕捉到怀孕的蓝鲨即将分娩这一事实表明，它们可能在相模湾等沿海地区分娩。由于延绳钓渔具的尺寸选择性，我们无法捕捉到幼鲨幼体。未来的研究，使用净抽样，将是必要的，以寻找新生的蓝鲨在这一沿海地区。
Blue shark (Prionace glauca) and shortfin mako shark (Isurus oxyrinchus) are recognized as pelagic sharks and highly migratory species, but these sharks appear in coastal areas. It is suggested that sharks migrate in the growth stage, but we do not know the details and how sharks use coastal areas. A fishing survey of these species in coastal areas like Sagami Bay is rare, and thus we carried out two types of longline operations to survey catch trends about the shark in Sagami Bay from August 2011 to July 2017: vertical and horizontal longline operations. Both species were caught throughout the year, with peaks in July and December for both blue sharks and shortfin mako sharks. Many of the male juvenile blue sharks caught had not reached sexual maturity, and pregnant blue sharks were also present among the females. The birthing period of blue sharks is reported to be from April to July, and the young are believed to be born and grow up in the open ocean of the North Pacific. However, the fact that we caught pregnant blue sharks close to giving birth suggests that they may give birth in coastal areas such as Sagami Bay. We were unable to catch young shark larvae because of the size selectivity of the longline fishing gear. Future studies, using net sampling, will be necessary to search for new-born blue sharks in this coastal area.