Aquaculture 612, 2, 743267. 2026. 

New publications Physiological and transcriptomic responses to fasting-refeeding in Arapaima gigas: Insights into compensatory growth for aquaculture production

Fish exhibit remarkably efficient feed conversion ratios (FCR), often outperforming homeothermic animals in terms of protein conversion efficiency — a feature that is increasingly relevant for sustainable aquaculture practices. Arapaima gigas, one of the largest freshwater fish species in the Amazon, is renowned for its exceptional FCR during the initial growth phase. The aim of this study was to evaluate whether a fasting-refeeding protocol could further enhance feed efficiency in A. gigas. The study examined its effects on growth performance, liver histology, and hepatic gene expression. The results of the study indicate that there is a loss of body weight after one to two weeks of fasting, as well as growth arrest in total length. In addition, there is liver shrinkage driven by hepatocyte size reduction. Following refeeding, liver and cell size recovered within a week, and fish resumed growth with significantly improved FCR. Treated fish demonstrated partial compensatory growth in both body weight and length, with sustained higher specific growth rates and feed intake relative to controls throughout the refeeding process. It is noteworthy that the refed group consumed 51 % less feed over the course of entire trial, which highlights the significant potential for substantial reduction in feed cost. Transcriptomic analysis revealed significant metabolic changes: fasting increased the expression of genes involved in lipid catabolism (e.g., RXRA, ABCA1, ACOT2), while early refeeding (3 days) activated pathways associated with gluconeogenesis (PPARGC1A, MDH1), and later refeeding (2 weeks) upregulated genes involved in mitochondrial repair and tissue regeneration (LIG3, A2MG). These findings offer a valuable contribution to the development of sustainable aquaculture practices for this fast-growing and threatened Amazonian species.

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