Management of Atlantic Bluefin Tuna (Thunnus thynnus) By-Products in Malta: Logistics, Biomass Quality and Environmental Impact

Malta produces approximately 15,000 tons of bluefin tuna every year and by-products are estimated to account for 55% of the harvest. Maltese tuna farmers established a company that processes these by-products into fish meal and oil that are sold to the pet food industry. In this study, the logistic of tuna farming and management in Malta was analysed and the environmental impact of the activity was estimated. The biomass quality and the preservation state of tuna head and liver were assessed. The head had the highest ash content (1.68 ± 0.02%) while the liver had the highest protein content (16.18 ± 0.02%) and the highest crude fat, (34.87 ± 0.76%). The highest concentration of oil was found in the head's skin (50.07 ± 0.84%). The predominant saturated fatty acids (SFAs) were c14:0, c16:0, and c18:0. Monounsaturated FAs (MUFAs) were the major fatty acids present in all samples, with the highest values in the tuna head. The oxidation levels found in the by-products upon arrival at the processing plant don't compromise their quality. No histamine formation was predicted. The Life Cycle Assessment estimated that the environmental score of the activity is 105 points per ton of fishmeal and 25 kg of oil produced (2.82 tCO₂ eq). It is concluded that the processing of tuna by-products in Malta is a sustainable alternative to traditional disposal methods and their quality is high enough to be used as a source of proteins and lipids in farmed-animals feed.