Effect of fishmeal and fish oil replacement by algal meals on biological performance and fatty acid profile of hybrid striped bass (Morone crhysops ♀ × M. saxatilis ♂)

A 6-week growth trial was conducted to assess the replacement of fishmeal (FM), soy protein concentrate (SPC) and fish oil (FO) by Arthrospira sp. and Schizochytrium limacinum meals in diets for hybrid striped bass (Morone chrysops × M. saxatilis) juveniles of 10.6 ± 0.2 g initial individual weight (±standard deviation). A control diet was formulated with equivalent contributions of FM and SPC to provide 40% crude protein. Menhaden FO was the main lipid source, providing 10% crude fat. Five experimental diets replaced 10, 20, 30, 40 and 50% of FM, SPC, and FO from the control diet by combining two algal meals derived from the freshwater autotroph Arthrospira sp. and the marine heterotroph S. limacinum. Each diet was randomly assigned to three replicate aquaria, and twelve group-weighed fish were stocked per aquarium. Fish were group-weighed weekly to adjust the feeding ration, which started at 6% and gradually decreased to 3%, confirmed by visual feeding cues to avoid overfeeding. At the end of the trial, no statistical differences for responses such as condition factor (P = 0.6778), hepatosomatic index (P = 0.4542), intraperitoneal fat ratio (P = 0.0997), or feed efficiency (P = 0.2210) were detected. However, statistically significant differences were observed for percent weight gain (WG; P = 0.0323) and thermal growth coefficient (TGC; P = 0.0164). Weight gain (209.5%) and TGC (0.088) of fish fed the control diet was significantly lower than in fish fed the 30 and 50% replacement diets (WG: 232.8–235.3%), but no differences were detected among fish fed any other replacement level (WG: 217.1–227.9%). Whole-body proximate composition showed no statistical differences among fish for crude protein, moisture, or ash, except for crude fat content (P < 0.0001); the highest percentage of fat (9.3%) was observed in fish fed the 30% replacement level. The dietary fatty acid profile influenced the fatty acid profile of fish, eliciting an increment in the content of specific fatty acids, such as 16:0, 18:2n-6 and 22:6n-3. Although higher docosahexaenoic acid (DHA) content was observed in whole-body of hybrid striped bass fed the experimental diets, this fatty acid did not contribute to a higher body lipid content. The findings indicate that the combination of Arthrospira sp. and S. limacinum meals can replace a significant proportion of fish-derived feedstuffs in hybrid striped bass feeds, promoting suitable growth performances with up to 50% replacement under these conditions, and promoting the accumulation of DHA in fish tissues, which would ultimately benefit consumers.