Reproductive Strategy of the Squid, Todarodes pacificus, Produce Large Gelatinous Egg Masses

通过野外调查和人工饲养试验，研究了太平洋褶柔鱼在种群数量波动下的繁殖策略。未成熟的鱿鱼被收集和保持在一个跑道坦克，他们成熟，交配和产卵。胶状卵块呈球形，几乎有浮力。最大的卵团直径为80厘米，约有20万枚卵。卵块表层有效地防止了甲壳类动物、原生动物和细菌侵扰卵块。在18-19℃条件下4-6天后，副栉孔扇贝孵化，并立即开始游动，个体数较多。卵块孵化后不久即解体。在3.5-29℃温度范围内对卵和幼虫的存活进行了研究，以确定发育和存活的最适温度范围。最高的胚胎存活率出现在15和23℃之间。证明T.在水温高于15℃的沃茨中产卵，卵块保持其结构， ...更多信息 在15 ~ 23℃的温度范围内，产卵期为4 ~ 9.5天，产卵后解体。据推测，日本周边太平洋小海龟的卵块和孵化发生在15至23℃的温度之间，并且在大陆架和斜坡之上，因为捕获的雌性在产卵前经常坐在池底。自20世纪80年代末以来，日本太平洋褶柔鱼的年渔获量逐渐增加。自1980年代后期以来，类幼体丰度也高于1970年代后期和1980年代中期。我们提出了一个可能的情况下，最近的库存增加的基础上不断变化的环境条件。首先，我们研究了种群和幼虫渔获量的年度变化趋势，并推断潜在的产卵区，假设卵块和孵化发生在15至23℃之间的温度，并在大陆架。然后，我们推断在产卵区的变化，在1984-95年的基础上GIS数据。我们的结论是，自20世纪80年代后期以来，秋季和冬季产卵区重叠在对马海峡和后藤群岛附近，冬季产卵场已扩大到大陆架和斜坡在东海。少

Reproductive strategy related to stock fluctuation on the ommastrephid squid Todarodes pacificus are examined by field survey and captive experiments. Immature squid were collected and maintained in a raceway tank where they matured, mated, and spawned. Gelatinous egg masses were spherical and nearly buoyant. The largest egg mass measured 80 cm in diameter and contained approximately 200,000 eggs. The egg-mass surface layer effectively prevented crustaceans, protozoans, and bacteria from infesting the masses. Paralarvae hatched after 4-6 days at 18-19℃ and actively swam at once, with many individuals swimming at the surface. Egg masses disintegrated soon after hatching. Survival of eggs and paralarvae were examined at temperatures ranged from 3.5-29℃ to determine the optimum temperature range for development and survival. Highest embryonic survival rates occurred between 15 and 23℃. It is sugggested that T. pacificus spawns in waters warmer than 15℃, and egg masses maintain their struc … More ture for about 4-9.5 days before disintegrating at temperatures between 15 and 23℃.The inferred spawning sites of T. pacificus around Japan are assumed that egg masses and hatchlings occur at temperatures between 15 and 23℃, and above the continental shelf and slope, because captive females regularly sit on the tank bottom just before spawning. Annual catches of Todarodes pacificus in Japan have gradually increased since the late 1980s. Paralarval abundances have also been higher since the late 1980s than during the late 1970s and mid-1980s. We propose a possible scenario for the recent stock increase based on changing environmental conditions. First, we examined trends in the annual variations of stock and larval catches, and infer potential spawninig areas, assuming that egg masses and hatchlings occur at temperatures between 15 and 23℃, and over the continental shelf. We then infer changes in the spawning areas during 1984-95 based on GIS data. We conclude that since the late 1980s the fall and winter spawning areas have overlapped in the Tsushima Strait and near the Goto Islands, and that winter spawning sites have expanded over the continental shelf and slope in the East China Sea. Less