Authors: Assistant Professor Dr. M. Stephen
Abstract: The rapid expansion of aquaculture and fish processing has increased the generation of nutrient-rich processing by-products, creating both an environmental challenge and an opportunity for circular bioeconomy development. Global aquaculture production of aquatic animals exceeded 100 million tonnes in 2024, while total global fisheries and aquaculture production reached approximately 235 million tonnes, highlighting the increasing volume of biomass entering aquatic-food value chains. Fish processing can generate approximately 30–70% of the original fish biomass as side streams, including heads, viscera, skin, bones, frames, fins and scales. These materials contain proteins, collagen, gelatin, peptides, lipids, omega-3 fatty acids, minerals and other bioactive compounds that can be recovered through extraction, hydrolysis, fermentation and biorefinery approaches. Tilapia processing provides a representative example: fillets generally constitute only 30–33% of whole-fish weight, leaving approximately 67–70% as processing by-products. Quantitative evidence demonstrates substantial recovery potential. Fish scales and bones can contain approximately 30–40% organic collagen matrix and 60–70% hydroxyapatite, while recent extraction approaches have reported collagen yields of up to 25–35%. Experimental studies have reported collagen yields ranging from less than 1% to more than 50%, depending on species, tissue, pretreatment and extraction method. Fish-processing lipids also represent an important source of omega-3 fatty acids, with EPA and DHA frequently detected at biologically relevant proportions in viscera, liver, heads and frames. This review quantitatively examines the magnitude of fish-processing waste, composition of major by-products, recovery of collagen, protein hydrolysates and omega-3 lipids, and their conversion into food, nutraceutical, pharmaceutical, cosmetic, biomedical, agricultural and biomaterial products. The review further evaluates technological limitations, economic considerations and future directions for integrated zero-waste aquaculture and fish-processing systems.
