Early starvation limits survival in amphidromous fishes

Newly hatched amphidromous larvae drift downstream to the sea. Since there is practically no food available for drifting larvae, an extended downstream migration may enhance the risk of starvation. We hypothesized that early survival of amphidromous fish varies among populations according to the length of the river, due to its effect on larval starvation. The hypothesis was tested with the common Japanese amphidromous goby, Rhinogobius brunneus. Based on morphological characteristics, larvae were categorized as being in an endogenous feeding state (EFS) or irrecoverable starved state(ISS). The frequency of ISS larvae in the population from a long river was nearly twice the frequency in the population from is short stream. More than half of larvae were judged to be dying during downstream migration in the comparatively long river, although this was possibly an underestimation. It is suggested that early starvation limits reproductive success far from the sea. (C) 1999 The Fisheries Society of the British Isles.

新孵化的溯河洄游性幼体顺流而下漂向大海。由于实际上没有可供漂流幼体获取的食物，长时间的顺流迁徙可能会增加饥饿的风险。我们假设溯河洄游性鱼类的早期存活率因河流长度不同而在种群之间存在差异，这是由于河流长度对幼体饥饿的影响。我们用日本常见的溯河洄游性虾虎鱼褐吻虾虎鱼（Rhinogobius brunneus）对这一假设进行了检验。根据形态特征，幼体被归类为处于内源性摄食状态（EFS）或不可恢复的饥饿状态（ISS）。来自长河的种群中ISS幼体的频率几乎是来自短溪种群的两倍。在相对较长的河流中，超过一半的幼体在顺流迁徙过程中被判定为濒死状态，尽管这可能是一种低估。研究表明，早期饥饿限制了远离海洋地区的繁殖成功率。（C）1999年不列颠群岛渔业协会。