Fatty acid requirements in ontogeny of marine and freshwater fish

TLDR

Fish essential fatty acid requirements differ by species and developmental stage, with freshwater species mainly needing C18 PUFA and marine species requiring long‑chain n‑3 PUFA, yet research on precise quantitative needs has lagged, especially as aquaculture shifts toward plant‑based feeds, raising concerns that growth‑optimal levels may not match nutritional quality requirements. The study aims to elucidate the biochemical and molecular mechanisms underlying fish EFA requirements and metabolism. Salmonids can be raised on vegetable oils lacking long‑chain n‑3 PUFA, but this compromises the health benefits for human consumers.

Abstract

Essential fatty acid (EFA) requirements vary qualitatively and quantitatively with both species and during ontogeny of fish, with early developmental stages and broodstock being critical periods. Environment and/or trophic level are major factors, with freshwater/diadromous species generally requiring C18 polyunsaturated fatty acids (PUFA) whereas marine fish have a strict requirement for long-chain PUFA, eicosapentaenoic, docosahexaenoic and arachidonic acids. Other than marine fish larvae, defining precise quantitative or semi-quantitative EFA requirements in fish have received less attention in recent years. However, the changes to feed formulations being forced upon the aquaculture industry by the pressing need for sustainable development, namely the replacement of marine fish meal and oils with plant-derived products, have reintroduced EFA into the research agenda. It is particularly important to note that the physiological requirements of the fish to prevent deficiency pathologies and produce optimal growth may not parallel the requirements for maintaining nutritional quality. For instance, salmonids can be successfully cultured on vegetable oils devoid of long-chain n-3 PUFA but not without potentially compromising their health benefits to the human consumer. Solving this problem will require detailed knowledge of the biochemical and molecular basis of EFA requirements and metabolism.