Biology and effects of cartilaginous fishes on fisheries in the Sagami Bay

本研究在相模湾150 m以下海域共采集到软骨鱼21种。渔民提供了三种鱼类。神奈川县渔业研究中心R/V Enoshima-maru捕获的442个标本中，三kurii角鲨（Squalus mitsukurii）的数量最多，占总捕捞量的69%。其他种类占总数不到10%。短刺狗鱼，s.m mitsukurii，深度150 - 550米，主要分布在300-400米之间。单位努力渔获量趋势（CUPUE）以每百次渔获量和单位网长表示的钩率表示，表明它们进行季节性垂直迁移，在温暖季节进入深水，而在寒冷季节则栖息在较浅的深度。但是，在东京湾入口附近的海底山，并没有在隆冬的沿海水域捕捉到它们。这表明海湾内也有更多的横向迁移。根据雄鱼的稀少和捕获的小样本，也建议按大小和性别进行隔离。利用胃内容物分析和受损鱼的牙痕，研究了三栗螺对相模湾分布的重要商业鱼类的捕食情况。结果表明，在垂直绳钓捕获的鱼类中，约有8%的鱼类遭到了三栗拟蟹的捕食。年龄和生长研究也使用标记在第二背鳍棘上的环。长石近海的生长曲线与以往研究结果接近，而与汉考克的小笠原和海山的生长曲线有较大差异。繁殖研究表明，三栗鼠的繁殖策略与长志地区的略有不同。胃内容物分析显示，相模湾地区之间似乎有一些差异，但与其他地区的研究报告一样，全是一种独家的食腐动物。利用氮碳稳定同位素比值分析了7种植物的取食状况。C-N图显示物种间的差异远小于生境间的差异。不同的生长阶段也不同。少

The total number of 21 species of cartilaginous fishes were collected from the depth below 150 m in the Sagami Bay during the course of the present study. Three triakid species were provided by fishermen. Among those species, most abundant species was Squalus mitsukurii, making up 69% of the total catch of 442 specimens captured by R/V Enoshima-maru belonging to Kanagawa Prefectural Fisheries Research Center. Other species constituted less than 10 % of the total.Shortspined dog fish, S.mitsukurii, ranged from 150 m to 550 m in depth, mainly between 300-400 m. Trend of catch per unit efforts (CUPUE) using hooked rates expressed by number caught per hundred hooks and unit net length, indicates that they made seasonally vertical migration and go into deep waters during warm seasons while they inhabit shallower depth during cold seasons. However, they were not caught in mid-winter in the coastal waters while they are captured in the seamount near the entrance of Tokyo Bay., suggesting hori … More zontal migration within the bay as well. Segregation by sizes and sexes were also suggested, judging from scarcity of males and small specimens in the catch. Predation by S.mitsukurii on commercially important fishes distributed in the Sagami Bay was also investigated using stomach contents analysis and tooth scars of damaged fishes. As a result, it is concluded that about 8 % of fishes caught by vertical loglines suffered from predation by S.mitsukurii. Age and growth studies were also conducted using annuli marked on second dorsal fin spines. Growth curves were close to those presented by the past studies in offshore area of Choshi while quire different from those in Ogasawara and Seamount of Hancock... Reproductive studies of S.mitsukurii indicate that reproductive strategy is a little different from that obtained from Choshi area. Stomach contents analysis reveals that there seemed to be a little different between regions in Sagami Bay but totally S.mitsukurii are an exclusive picivore as reported by other studies in other regions. Feeding status of seven species was analyzed using stable isotope ratio of nitrogen and carbon. C-N maps indicated that differences between species are rather smaller than differences between habitats. They also differed according to growth stage. Less