Convergent responses of fish belonging to different feeding guilds to sewage pollution

ABSTRACT This study aimed to evaluate if the presence of pollutants promotes changes in feeding habits of fish species from different trophic guilds: the detritivorous species, Hypostomus francisci, and the piscivorous, Hoplias intermedius. Both species were sampled at 12 sites (with different degrees of pollution) in the Rio das Velhas basin, which is heavily polluted by domestic and industrial sewage from the Metropolitan Region of Belo Horizonte (MRBH). Stable isotope analyses of carbon (δ13C) and nitrogen (δ15N) of fish tissue and the main food resources were performed. Fishes from both trophic guilds altered their diets in degraded environments, but the detritivorous species showed greater trophic plasticity. The isotopic niche of both trophic guilds was broadest in unpolluted sites and more δ15N enriched in polluted regions. The detritivorous species presented high niche-breadth in unpolluted sites, probably due to the greater variety of resources consumed. In addition, the δ15N of the detritivorous was more enriched than the piscivorous species in polluted sites. In conclusion, fishes from both trophic guilds presented similar isotopic responses to environmental pollution. However, the detritivorous species was more sensitive to these alterations and therefore, is likely a better indicator of environmental condition than the piscivorous.

摘要：本研究旨在探究污染物的存在是否会改变不同营养功能群（trophic guilds）鱼类的食性，研究涉及食碎屑性物种Hypostomus francisci与食鱼性物种Hoplias intermedius。两种鱼类均在受贝洛奥里藏特大都会区（Metropolitan Region of Belo Horizonte, MRBH）生活与工业污水严重污染的韦利亚斯河盆地的12个污染程度各异的样点中完成采样。研究人员对鱼类组织及主要食物资源开展了碳（δ13C）与氮（δ15N）的稳定同位素分析。结果显示，两个营养功能群的鱼类在退化环境中均改变了自身食性，但食碎屑性物种表现出更强的营养可塑性。两类营养功能群的同位素生态位在未污染样点中宽度最广，而在污染区域的δ15N富集程度更高。食碎屑性物种在未污染样点中拥有较高的生态位宽度，这可能与其摄取的资源种类更为多样有关。此外，在污染样点中，食碎屑性物种的δ15N富集程度高于食鱼性物种。综上，两个营养功能群的鱼类对环境污染均表现出相似的同位素响应。然而，食碎屑性物种对这类环境改变更为敏感，因此相较于食鱼性物种，其更适宜作为环境状况的生物指示物。