Effects of varied exercise intensities on growth, muscle quality and volatile compounds in largemouth bass ( Micropterus salmoides ) cultured in recirculating aquaculture system

To explore the impact of different exercise intensities on the growth, muscle quality, and volatile compounds of largemouth bass, this study involved 270 fish with an initial weight of 96.05 +/- 18.87 g. They were divided into three groups: a control group (CG) exposed to a constant current speed of 0.30 cm/s for 24 h/day; an interval exercise group (IE) exercising at a rate of 2 body lengths per second (bl/s) for 8 h/day; and a sustained exercise group (SE) exercising continuously at 2 bl/s for 24 h/day. The experiment was conducted in a recirculating aquaculture system over a period of 90 days. Results revealed that SE exhibited remarkably greater body mass and condition factor (CF), with higher weight gain rate (WGR) and specific growth rate (SGR) compared to IE and CG (P < 0.05). SE exhibits superior growth performance. No significant differences was observed among the three groups in terms of centrifugal loss, drip loss, liquid loss, stored loss, and cooked rate. However, in terms of frozen leakage, the IE was considerably lower than the CG and SE (P < 0.05).In terms of raw meat texture, the hardness, chewiness, and shearing of the SE were notably greater than the CG (P < 0.05), and the SE were superior in hardness compared to the IE (P < 0.05). Regarding cooked meat texture, the SE exhibited significantly superior hardness, chewiness, springiness, and shearing compared to both the CG and IE (P < 0.05). The IE demonstrated higher levels of chewiness, springiness, and shearing compared to the CG (P < 0.05). With respect to nutritional indicators, the crude protein content of both the SE and IE was significantly higher than that of the CG. In terms of volatile substances, the CG had relatively high levels of carboxylic acid compounds and alcohol compounds in this experiment. The ketone compounds in the IE were significantly higher than those in the CG and SE. 2-Methylbutanoic acid methyl ester had the highest content in the SE. The results show that interval swimming exercise training and sustained exercise training can effectively improve the sensory quality of fish muscle, effectively remove the irritating smell in the muscle, and produce aromatic odor. Consequently, exercise training at varying intensities has been demonstrated to significantly enhance the growth and muscle quality of largemouth bass, offering potential strategies for improving fish product quality in the aquaculture industry. This contributes to increased efficiency and sustainability in fish farming practices and provides valuable insights for regulating the nutritional quality of fish muscle in future recirculating aquaculture system models.