Fatty acid requirements in ontogeny of marine and freshwater fish

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 has 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, has 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

Compared to fish oil alone, a corn and fish oil mixture decreases the lipid requirement of a freshwater fish species, Carassius auratus gibelio

“…18:2n− 6 is considered as the essential fatty acid (EFA) and its requirement is reported 1% of the dry diet for common carp Cyprinus carpio L. and grass carp Ctenopharyngodon idella Valenciennes (Tocher, 2010). 18:2n− 6 is considered as precursor of the synthesis of 20:4n− 6 through a series of desaturation and elongation steps in vivo (Owen et al, 1975).…”

“…It is generally considered that freshwater omnivorous, planktivorous or herbivorous species can convert 18:2n− 6 and 18:3n− 3 into LC-PUFA at a sufficient rate to meet their minimum requirements which play an important role in membrane structure and function, and providing energy during embryonic and early larval development in fish, but the ability is generally much lower, or even absent, in marine species (Sargent et al, 2002;Tocher, 2010). For marine species, fish oil may be the suitable dietary lipid source, but for these freshwater species, plant oil may be the reasonable diet lipid source as well as fish oil (De Silva et al, 2010;Gunstone and Harwood, 2007;Tocher, 2010;Turchini et al, 2009).…”

“…For marine species, fish oil may be the suitable dietary lipid source, but for these freshwater species, plant oil may be the reasonable diet lipid source as well as fish oil (De Silva et al, 2010;Gunstone and Harwood, 2007;Tocher, 2010;Turchini et al, 2009). Numerous studies have investigated the use of plant oil to replace fish oil in the formulation of aqua-feeds of cultured species in recent years; however, dietary lipid requirement data obtained for most freshwater or marine cultured species were based on fish oil as the lipid source (Ghanawi et al, 2011;Pei et al, 2004;Peres and Oliva-Teles, 1999).…”

Cloning and Characterization of Lxr and Srebp1, and Their Potential Roles in Regulation of LC‐PUFA Biosynthesis in Rabbitfish Siganus canaliculatus

“…(20:5n-3, EPA) and docosahexaenoic (22:6n-3, DHA) acids, are essential fatty acids 73 (EFA) for marine teleosts which, compared to freshwater and salmonid species, are 74 historically regarded as species with limited capability for LC-PUFA biosynthesis 75 from C 18 PUFA precursors [1,2]. Hence in aquaculture, LC-PUFA-rich fish oil (FO) 76 is utilized in feeds to satisfy the EFA requirement of marine teleosts [1].…”

“…Hence in aquaculture, LC-PUFA-rich fish oil (FO) 76 is utilized in feeds to satisfy the EFA requirement of marine teleosts [1]. However, FO 77 is derived from wild capture fisheries that have reached their maximum sustainable 78 level, and this has paradoxically constrained the development of marine aquaculture.…”