Indoor Recirculating Aquaculture Versus Traditional Ponds: Effects on Muscle Nutrient Profiles, Texture, and Flavour Compounds in Largemouth Bass (Micropterus salmoides)

This study compared the muscle quality of largemouth bass (<i>Micropterus salmoides</i>) reared in a simplified indoor factory-scale recirculating aquaculture system (F-RAS) with those reared in a traditional pond (TP). Juveniles from the same cohort (with a mean initial body mass of approximately 16 g) were stocked into the two systems and reared for ten months. The F-RAS is a high-density indoor system utilising octagonal concrete tanks with an effective water volume of 100 m³ and a stocking density of 130 fish m^-3. The TP is a low-density system, where fish are reared in earthen ponds with a total area of 4000 m² at a density of 1.7 fish m^-3. At the end of the experiment, 20 fish per group were randomly sampled for morphological analysis, while subsets of 6 fish per group were used for texture analysis, 3 fish per group for water-holding capacity, 3 fish per group for proximate composition, and 9 fish per group (pooled into 3 biological replicates) for amino acid, fatty acid and volatile compound analyses. The results showed that the F-RAS group exhibited superior texture, with significantly higher chewiness, springiness and muscle fibre density. Nutritionally, the F-RAS group had significantly greater crude protein, EPA, DHA and total n-3 fatty acid contents. Although glutamate and leucine levels were lower in the F-RAS group, cysteine and histidine levels were higher. Analysis of volatile compounds indicated improved flavour in the F-RAS group, with a marked reduction in off-flavour compounds such as 1-octen-3-ol and hexanal. Overall, largemouth bass produced in F-RAS showed better muscle quality than those from the TP in terms of texture, nutritional value and flavour. This study provides a reference for future research on the regulation of muscle quality in largemouth bass using a simplified F-RAS.