Miyasaka H, Nakano S
Tomakomai Research Station, Hokkaido University Forests, Takaoka, Tomakomai, Hokkaido 053-0035, Japan, e-mail:
Oecologia. 1999 Jan;118(1):99-106. doi: 10.1007/s004420050707.
Differences in the effects of two common predatory fishes, rainbow trout (Oncorhynchus mykiss) and freshwater sculpin (Cottus nozawae), on drift dispersal of the nymphs of three mayfly species, Baetis thermicus, Cinygmula sp., and Paraleptophlebia chocorata, were examined by manipulative field experiments using stream enclosures in a northern Japanese stream. The diel periodicity of prey consumption rate differed considerably between the two fishes; the prey consumption of the drift-foraging trout was greater at both dawn and dusk, whereas the benthic-foraging sculpin showed a higher consumption rate at night. The drift propensity at night was much greater than during the day for all the mayfly species in each of the trout, sculpin and fishless treatments, as well as under natural conditions with both fishes present. The nighttime drift propensities of the epibenthic grazers, B. thermicus and Cinygmula sp., were greater in the sculpin treatment than in trout and fishless treatments, and they did not differ between the trout and fishless treatments. By contrast, the nighttime drift propensity of P. chocorata, an infaunal collector-gatherer, did not differ among the treatments. The daytime drift propensity did not differ among the treatments for any of the mayfly species. Thus differences in drift response to the predatory fishes could be related to the characteristic microhabitats of the mayfly species. Moreover, the experiments demonstrated that benthic-foraging sculpin had greater overall effects on prey drift than drift-foraging trout.
在日本北部的一条溪流中，通过使用溪流围隔进行的操纵性野外实验，研究了两种常见的捕食性鱼类——虹鳟（Oncorhynchus mykiss）和淡水杜父鱼（Cottus nozawae）对三种蜉蝣若虫（Thermicus短脉蜉、Cinygmula属蜉蝣和Paraleptophlebia chocorata）漂流扩散的影响差异。两种鱼类的猎物消耗率的昼夜周期性差异很大；漂流觅食的虹鳟在黎明和黄昏时的猎物消耗量都更大，而底栖觅食的淡水杜父鱼在夜间的消耗率更高。在虹鳟、淡水杜父鱼和无鱼处理中，以及在两种鱼类都存在的自然条件下，所有蜉蝣物种在夜间的漂流倾向都远大于白天。在淡水杜父鱼处理中，底栖食草动物Thermicus短脉蜉和Cinygmula属蜉蝣在夜间的漂流倾向比在虹鳟和无鱼处理中更大，并且它们在虹鳟和无鱼处理之间没有差异。相比之下，穴居收集者Paraleptophlebia chocorata在夜间的漂流倾向在各处理之间没有差异。对于任何蜉蝣物种，白天的漂流倾向在各处理之间没有差异。因此，对捕食性鱼类的漂流反应差异可能与蜉蝣物种的特征微生境有关。此外，实验表明，底栖觅食的淡水杜父鱼对猎物漂流的总体影响比漂流觅食的虹鳟更大。
