Fish by-products as reliable proxies to evaluate nutritional fatty acid contents in commercial fish fillets.

Despite seafood being the primary source of long-chain omega-3 polyunsaturated fatty acids (PUFAs), the fatty acid (FA) contents of numerous exploited fish species remain unknown, partly due to the prohibitive costs associated with sourcing commercial fish fillets. We assessed whether fish by-products can reliably be used to estimate key nutritional FA contents in fillets by testing for consistent relationships between FA contents in fillet, and those in the breast, cheek, occiput, and tail tissue of three commercial coral reef fish species. Breast tissue was most suitable for estimating concentrations and proportions of FAs in the fillet due to strong and consistent relationships across FA types and species. In contrast, relationships between FA contents in the fillet and in other by-products were inconsistent across species and/or FA types. Through reducing research costs and food waste, utilising by-products will encourage FA research, particularly in tropical regions where omega-3 deficiency rates are highest.