The aquafeed industry is showing a growing interest in alternative raw materials such as fish by-products (heads, bones, viscera, gills, spines, fins and skin), to be used as feed for aquatic organisms due to the overexploitation of conventional marine resources .
The aim of this study was to evaluate the use of bluefin tuna side-streams from a Maltese fish farm as a fishmeal replacement in formulated diets for European seabass (Dicentrarchus labrax).
The trial was conducted in a 12 x 650L RAS system . Three experimental diets with 10%, 20% and 50% fishmeal replacement (10TBM, 20TBM and 50TBM) were formulated to be isonitrogenous, isolipidic and isoenergetic, and were tested in triplicate. European seabass, Dicentrarchus labrax (100 fish/tank; initial weight of 17.49 ± 0.04g ; stocking density of 2.7kg/m3) . Fish were fed four times a day until satiation for 10 weeks , after which a bulk weight of each replicate was performed. 5 fish from each tank were randomly selected to record total weight and length as well as liver, spleen and total viscera weight . Growth performance (FCR, SGR, SFR%, feed intake) as well as K, VSI, HSI, SSI, were evaluated and compared among diets.
Overall, there were no significant differences in growth and biometric indexes among the treatments. Fish fed 10TBM showed comparable growth to the control diet (69.36±3.33g and 69.42±2.64g), while fish fed TBM20 and TBM50 had slightly lower growth values (67.36±3.83g and 65.82±1.84g). FCR, SGR , SFR%, and feed intake also showed no significant differences among treatments . The K factor was highest in fish fed 10TBM (1.34±0.03) and the lowest in fish fed the CTRL diet (1.31±0.03). VSI showed the lowest value in fish fed 10TBM (12.38±1.41) and the highest value in fish fed 20TBM (13.03±0.68). The HSI and SSI indexes followed a similar pattern, with the highest values recorded in fish fed CTRL and 10TBM diets and the lowest in the remaining treatments.
The tuna -based fish meal proved to be an efficient protein source .
Acknowledgements
This research was conducted under the Profius project , funded by the European Union’s Horizon 2020 research and innovation programme Grant Agreement No: 817992.