The relative contribution of natural feed sources and commercial diets to the nutrition of Nile tilapia (Oreochromis nilloticus) was evaluated in a net cage production carried out in a reservoir in the semi-arid northeast region of Brazil. The present study tested the hypothesis that tilapia uses natural sources of feed for growth, even when confined in cages and artificial feed resources are available. The fish and various feed sources (commercial feed, seston and periphyton) were sampled and the water quality was monitored during the cultivation, which was carried out for 120 days. The fish were fed three times daily with two commercial feeds of 40 and 32 % crude protein, both of which used fish meal as a protein source. Stable isotopes analyses were carried out by measuring the ¹³C and ¹⁵N of fish muscle tissue and the feed items using the MixSIAR mixing model to determine the relative contribution of the nutrient sources to fish growth. The tilapia showed adequate weight gains with the total contributions of the feed items: periphyton (14.4 %), seston (51.2 %) and commercial feed (34.4 %) throughout the 120 days of culture. It can be concluded that the natural feed sources of seston and periphyton contributed more to the growth of the Nile tilapia than the commercial feed when cultivated in net cages, changing the notion that the commercial feed contributes predominantly to the intensive farming of this species in cages. The results of the present study suggest a more sustainable feed management in the farming of Nile tilapia in net cages.

在巴西半干旱东北地区的一个水库进行的网箱生产中，评估了天然饲料来源和商业日粮对尼罗罗非鱼（Oreochromis nilloticus）营养的相对贡献。本研究检验了罗非鱼使用天然饲料来源进行生长的假说，即使罗非鱼被关在笼子里并且有人工饲料资源也是如此。对鱼和各种饲料来源（商业饲料，色母和附生植物）进行采样，并在养殖过程中对水质进行监测，该过程进行了120天。每天给鱼饲喂三次，分别使用两种分别含40％和32％粗蛋白的商业饲料，这两种饲料均使用鱼粉作为蛋白质来源。稳定同位素分析通过测量^13种C和¹⁵ N的鱼肌肉组织和饲料项目使用MixSIAR混合模型确定营养源对鱼类生长的相对贡献。在整个120天的养殖过程中，罗非鱼的饲料总添加量显示出适当的增重：浮游植物（14.4％），芝麻油（51.2％）和商业饲料（34.4％）。可以得出结论，当在网箱中养殖时，天然饲料来源的塞斯顿和浮游生物对尼罗罗非鱼的生长比对商业饲料的贡献更大，这改变了商业饲料主要对这种物种在网箱中的集约化养殖做出贡献的观念。 。本研究结果表明，在网箱养殖尼罗罗非鱼方面，饲料管理更加可持续。