This study investigated whether aquaculture facilities drive the introduction and establishment of the non-native Nile tilapia (Orechromis niloticus) in Neotropical streams, Brazil. Samples were taken from nine streams with different aquaculture occupation intensities (no, moderate, and intense) using the percentage of occupation of micro-watersheds by aquaculture ponds as a proxy for propagule pressure. The presence of aquaculture facilities and the percentage of aquaculture occupation were good predictors of the catch frequency and of densities of tilapias in the adjacent natural environment. In the streams under intense propagule pressure, females prevailed and high densities of young individuals comparing to adults were recorded. It suggests that the species was reproductively successful in the natural environment. In the streams under moderate propagule pressure, males prevailed, which indicates the likely capture of individuals escaped from aquaculture facilities. In general, our results show the positive influence of propagule pressure on the introduction and establishment of Nile tilapia in natural ecosystems, showing that aquaculture expansion of O. niloticus poses a threat to the conservation of aquatic biodiversity.

中文翻译：

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水产养殖设施推动了新热带河流中非本地尼罗罗非鱼种群的引入和建立

本研究调查了水产养殖设施是否推动了巴西新热带河流中非本地尼罗罗非鱼（Orechromis niloticus）的引入和建立。使用水产养殖池塘对微型流域的占用百分比作为繁殖压力的代理，从具有不同水产养殖占用强度（无、中等和强烈）的九个溪流中取样。水产养殖设施的存在和水产养殖业的百分比是邻近自然环境中罗非鱼捕捞频率和密度的良好预测指标。在强烈繁殖压力下的溪流中，雌性占优势，与成年个体相比，年轻个体的密度高。这表明该物种在自然环境中繁殖成功。在中等繁殖压力下的溪流中，雄性占优势，这表明可能捕获了从水产养殖设施中逃脱的个体。总的来说，我们的结果表明繁殖压力对自然生态系统中尼罗罗非鱼的引入和建立有积极影响，表明罗非鱼的水产养殖扩张对水生生物多样性的保护构成了威胁。