In recent years, there has been a growing interest in finding innovative and eco-friendly protein sources for the aquaculture industry. Single-cell protein (SCP) has emerged as a promising candidate, particularly for juvenile fish diets. Formulating diets for larval stages, however, is inherently complex, making the incorporation of alternative protein sources not always a top priority. Therefore, research on its efficacy in larval fish diets is limited. Nonetheless, early inclusion of such ingredients could potentially enhance productivity during the juvenile phase and contribute to environmental stewardship. This study aimed to verify if SCP could be implemented as an effective protein source in larval diets without impacting the larval development of one of the most important cultured marine fish species in Europe, the gilthead sea bream (Sparus aurata).
Two different experimental co-feeding diets (D1 and D2, respectively) were formulated to have similar proximate composition. A SCP meal (FeedKind, Calysta, USA) was included as a novel ingredient in D1 at a level of 8%, while in D2, most of the protein sources originated from marine derivates as in diet D1, with an inclusion of a 5% vegetable protein source. Following pulverization and mixing of the dietary ingredients, agglomeration was performed using a laboratory scale spheronizer by atomization of a binder solution. The particles were dried at 60°C for 15 min followed by sieving to obtain 100-200 µm and 200-400 µm fractions of each diet.
Sea bream larvae were stocked at a density of 100 larvae.L-1 in 1000 L tanks, provided with water in a semi-closed recirculation system. The treatments consisted of providing the fish with the two different diets in triplicate tanks under a standard feeding regime, and being maintained under optimal conditions for this species.
As can be seen in Table 1, the performance of the fish in terms of survival, standard length, individual wet weight, and overall tank biomass was similar between the two diets. However, interestingly, the D1 group resulted in a higher percentage of bigger fish in its population than D2. To the best of our knowledge, this is the first study that shows the potential of incorporating this innovative ingredient into diets designed for marine fish larvae. This demonstrates the potential of integrating SCP into the larval diets of economically significant marine fish species.