Partial replacement of Artemia sp. by Moina sp. as live feed and early weaning onto a commercial diet: effects on growth, survival, and digestive histology of paiche (Arapaima sp.) juveniles

Paiche (Arapaima sp.) is an emblematic species of the Peruvian Amazon, yet sustainable production remains constrained by the limited availability of fry in captivity. This study aimed to evaluate the partial replacement of Artemia sp. by Moina sp. during the live-feeding phase and the effect of early weaning onto a commercial trout diet on growth, survival, and digestive system histology. The 37-day feeding trial was conducted with six treatments in triplicate, defined by three weaning sizes (3, 3.5, and 4 cm total length) and two live-feed regimes (100% Artemia sp. or 50% Artemia sp. + 50% Moina sp.). All groups were weaned onto the same commercial diet. Results showed that replacing 50% of Artemia sp. with Moina sp. did not compromise initial performance. However, fry assigned to weaning at 4 cm showed reduced growth while remaining exclusively on live feed, suggesting limitations of the live-feeding protocol at that size. Weaning at 4 cm was associated with better growth and survival indicators than weaning at 3 and 3.5 cm. Nonetheless, the commercial trout diet was unsuitable for early weaning, as evidenced at the histological level by alterations such as lumen obstruction, villi deterioration, and intestinal epithelial hyperplasia. Overall, these results highlight the need to develop paiche-specific starter diets tailored to the requirements of early life stages.