Aquaculture activities associated with the invasion of Oreochromis niloticus and changes in stream fish diversity

The objective of this research was to evaluate changes in fish diversity in streams subjected to different intensities of aquaculture production. The differences in the percentage of occupation by aquaculture ponds were used as a proxy for the propagule pressure of Oreochromis niloticus in natural environments and allowed for the classification of streams into three propagule pressure categories: no propagule, moderate, and intense. A species-rank abundance in the three propagule categories was conducted. Fish presence and absence data, and abundance of fish species were used as proxy to test the effect of aquaculture on fish assemblages. A total of 70 species were sampled, and O. niloticus was captured only in streams where aquaculture was developed. We found that O. niloticus increases its abundance as aquaculture propagule pressure also increases. Oreochromis niloticus was the 17th most abundant species in the moderate category, and the 6th species in the intense category. Fish composition (presence x absence, and abundance data) differed significantly among the propagule pressure categories, with species richness greater in no propagule pressure. These findings reinforce the role of aquaculture as a vector of invasive fish into Neotropical streams, where they can develop self-sustainable populations and impact native fish diversity.