Omega-3 Futures in Aquaculture: Exploring the Supply and Demands for Long-Chain Omega-3 Essential Fatty Acids by Aquaculture Species

Long-chain polyunsaturated fatty acids (LC-PUFA), like 22:6n-3 (Docosahexaenoic acid; DHA) and 20:5n-3 (Eicosapentaenoic acid; EPA), are recognized for a range of important physiological roles in many aquaculture species. While the effects of EPA and DHA on a range of performance attributes and meat qualities are well recognized, an increasing awareness of their role in immune function, reproduction, bone formation and stress response is also emerging. Against this background of demand, global supplies of LC-PUFA are dominated by fish oil production from a diversified range of sources, though news sources are emerging. Among those aquaculture sectors that are the largest users of LC-PUFA resources (salmonids, shrimp, and marine fish), there are varying degrees of capacity by each to endogenously synthesize LC-PUFA and this affects the degree to which they must be obtained via the diet. Salmonids, which are the largest user of these nutrients possess some capacity to make EPA and DHA de novo, although evidence supports that salmonids perform better when provided with them preformed. Requirements by shrimp for LC-PUFA are variable, with evidence indicating that some species have capacity to desaturate and elongate fatty acids, whereas others do not. This is consistent with the observation that some species can utilize short-chain polyunsaturated fatty acids, whereas others need pre-formed LC-PUFA in their diet. A third group, marine fish, have limited ability to desaturate and elongate precursor fatty acids and therefore have a critical requirement for LC-PUFA in their diet. Evidence across multiple species indicates that demands for these fatty acids are greater when the animals are young, and this demand decreases as they age. Among the various marine fish species examined estimates of requirements vary substantially and a one-size-fits all approach is clearly not applicable.