Experimental analyses on the effect of the larval growth rate to the predation mortality of small pelagic fishes

鱼苗的生长速度代表了这些阶段的生存潜力，在生存动态中起着关键作用。快速成长的个体更有可能生存的范式已经通过大量的研究出现，并导致了各种实地研究设计，尽管有一些相互矛盾的观察结果。Anderson（1988）的结论是，增长率和死亡率的联系理论提供了一个合理的框架，但这种关系仍有待量化。为了阐明生长速度如何调节生存，我们进行了实验分析，证明了环境和生物因素之间的关系，包括生长速度和营养状况，以及游泳活动，这些因素与捕食风险的逃脱能力高度相关。我们的研究主要采用了两种方法。1)测定日本鳀鱼幼鱼（Engraulis japonicus）幼鱼在温度为17 ~ 27℃的水洞（长100 cm、深30 cm、宽30 cm）中60 min…More s的耐力速度。分别测量游泳起始时间，实验结束后测量生物参数（体长、体重、内脏重量和胃内容物重量）。耐力时间随温度和几个生物学参数的变化而变化，随体长比速的增加而减小。2)不同鱼群位置取样装置设计了不同鱼群位置取样装置。在上述水洞中安装了选样仪。对日本凤尾鱼幼鱼进行了十多次抽样试验。每鱼群中快、中、慢三组幼鱼同时取样。耳石分析结果表明，幼虫生长速度与鱼群位置之间无明显关系。少

INTRODUCTION Growth rates of fish larvae represent survival potential during these stages, playing a key role in survival dynamics. The paradigm that faster-growing individuals are more likely to survive has emerged through numerous studies, and led to various field study designs, although there have been some conflicting observations. Anderson(1988) concluded that the theory linking growth rate and mortality provides a rational framework, but that the relationship remains to be quantified. To clarify how growth rates regulate survival, experimental analyses were conducted to demonstrate the relationships between environmental and biological factors, including growth rate and nutritional condition, and swimming activity which highly related to the escape ability from the predation risks. Two major approaches were adopted in our study.1) Measurement of the endurance speed of young Japanese anchovy Young fishes of Japanese anchovy, Engraulis japonicus, were used for measuring of 60 minut … More es endurance speed in a water tunnel(100 cm long x 30 cm depth x 30 cm width) at a temperature of 17-27℃. Elapsed time from start of swimming were measured individually and biological parameters(body length, body weight, visceral weight and weight of stomach content) were measured after the experiments. Endurance time changed depending on temperature and several biological parameters, and decreased according with the increase of specific speed in body length.2) Sampling instrument for selecting fishes in the different school positions A sampling instrument for selecting fishes in the different school positions was designed. The selecting sampling instrument was built and attached in the water tunnel mentioned above. More than ten times sampling trials were done on the young fishes of Japanese anchovy. Fast, middle and slow group of young fishes in each school were sampled at the same time. Results of otolith analyses indicated no clear relationships between the larval growth rate and the position in the school. Less