Diet and trophic interactions between catadromous eels and sympatric fish in Kenyan east flowing river systems

Japhet K. Tembo, C. Kihia, Nzula Kitaka, Gordon C. O'Brien, Céline Hanzen, E. Mbaru, Kariuki C. Wanjiru
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Abstract

Biotic interactions such as competition and predation are important ecological drivers of population structure. Interactions among higher trophic level fish can contribute to further population declines in species, such as eels, made vulnerable by overexploitation or environmental change. Furthermore, trophic interactions may further predispose eel populations to collapse, but this is poorly understood, particularly along the Western Indian Ocean (WIO) rivers. This study evaluated stomach contents of fish captured with glass and commercial fyke nets in the Athi and Ramisi Rivers, which discharge into the WIO. Stomach contents were examined using dissecting microscope to establish diet composition. Eels primarily consumed assorted fish (43 %), and crustaceans (36 %); such as penaeid shrimp (14%) and prawns (13%) and crab (9%), thus belonged to a higher trophic level (TL) of 3.47 than native (2.98) or introduced (2.8) sympatric fish species. Diet breadth of eels was significantly lower (0.20) than for sympatric fish species (0.27), attributed to higher diet specialization. The TL of carnivorous fish (3.19) and their diet compared well with those of eels, even though diet preference differed significantly among fish types. Consequently, eels ranked as vulnerable by the IUCN are further threatened by previously undescribed competition from carnivorous fish.
肯尼亚东流河系溯河鳗鱼与同域鱼类之间的饮食和营养相互作用
竞争和捕食等生物相互作用是种群结构的重要生态驱动因素。高营养级鱼类之间的相互作用会导致鳗鱼等物种的种群数量进一步下降,而过度捕捞或环境变化又会使这些物种变得脆弱。此外,营养级之间的相互作用可能会进一步导致鳗鱼种群的崩溃,但人们对这一点还知之甚少,尤其是在西印度洋(WIO)河流沿岸。这项研究评估了在排入西印度洋的阿蒂河和拉米西河用玻璃网和商业刺网捕获的鱼类的胃内容物。使用解剖显微镜检查胃内容物,以确定食物组成。鳗鱼主要摄食各种鱼类(43%)和甲壳类(36%),如对虾(14%)、对虾(13%)和螃蟹(9%),因此其营养级(TL)为3.47,高于本地鱼类(2.98)或引进鱼类(2.8)。鳗鱼的食物广度(0.20)明显低于同域鱼类(0.27),这归因于其较高的食物专一性。肉食性鱼类的TL(3.19)和它们的食物与鳗鱼的TL(3.19)相比较,尽管不同种类鱼类对食物的偏好有很大差异。因此,被世界自然保护联盟列为易危物种的鳗鱼正受到肉食性鱼类的进一步威胁。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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