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Reproductive characteristics of the Ryukyu-ayu, Plecoglossus altivelis ryukyuensis

琉球香鱼 Plecoglossus altivelis ryukyuensis 的繁殖特性

基本信息

批准号：
06660248
负责人：
TAKANO Kazunori
金额：
$ 1.28万
依托单位：
University of the Ryukyus
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06660248/
关键词：
Ryukyu-ayu maturation growth egg quality

项目摘要

The ayu population in Amami-oshima and Okinawa Island was described as a subspecies (Plecoglossus altivelis ryukyuensis). Little is, however, known about the reproductive characteristics of this subspecies. Recently, aquaculture production of young fish has been conducted to be released into the river, and to restore the ayu which once disappeared in Okinawa Island.In the process of aquaculture production, overripe ovarian eggs were often observed in cultured females. In this study, the syu reared under ambient condition were transferred to long photoperiod (18L6D) condition in June. Uuder this condition, females remained suppressed in summer and autumn, while control group under ambient condition attained maturity in the late November. When they were returned to the condition of natural day-length, gonadal maturation proceeded rapidly and resulted in spawning eggs with high fertilizability compared with that of control group after about a month.It is known that the spawning season of broodstock is earlier than that of native stock in the river. The effect of delay of growth, which is caused by feed restriction, was investigated. The treatments were normal feed (CF,standard feed)and low feed (LF,feed at 1/3 of CF). After the commencement of experiment at June 20, body length and GSI were significantly lower in the LF group than that in the CF group throughout the experimental period. Size differences reflected differences in start of vitellogenesis and maturation. Ovulation was observed during the period from the late November to the early December in the CF group in which 42 females had overripe eggs. On the contrary, ovulation occurred in the middle of December in LF group in accompanying only one overriped female.Based on these results, it is suggested that the growth of the ayu is important factor affecting the start of spawning season in the native river.

奄美大岛和冲绳岛的香鱼种群被描述为一个亚种（Plecoglossus altivelis ryukyuensis）。然而，人们对这个亚种的繁殖特征知之甚少。最近，进行了幼鱼的水产养殖生产，将其放回河中，以恢复冲绳岛曾经消失的香鱼。在水产养殖生产过程中，经常在养殖的雌鱼中观察到过熟的卵巢卵。在这项研究中，在环境条件下饲养的syu于6月份转移到长光周期（18L6D）条件。在这种条件下，雌虫在夏秋季节仍处于抑制状态，而常温条件下的对照组在11月下旬达到成熟。当恢复到自然日长状态后，性腺成熟迅速进行，约一个月后产卵量与对照组相比，受精率较高。已知亲鱼的产卵季节早于河流中的原生种群。研究了由饲料限制引起的生长延迟的影响。处理为正常饲喂(CF，标准饲喂)和低饲喂(LF，饲喂量为CF的1/3)。 6月20日实验开始后，整个实验期间LF组的体长和GSI均显着低于CF组。大小差异反映了卵黄发生和成熟开始的差异。 CF组在11月下旬至12月上旬期间观察到排卵，其中42只雌性卵子过熟。相反，LF组的排卵发生在12月中旬，仅伴随一只过熟的雌鱼。根据这些结果，表明香鱼的生长是影响本地河流产卵季节开始的重要因素。