Effects of flow velocity on the muscle nutrient content and flesh quality of the Pacific abalone (Haliotis discus hannai)

The aim of this study was to determine the effects of flow velocity (FV) on the growth and muscle texture of Pacific abalone (Haliotis discus hannai). Abalones were cultured at three sites for 90 days: LJ (119.912°E, 26.398°N), DS (119.903°E, 26.372°N), and JJ (119.875°E, 26.361°N). The FVs of the LJ, DS, and JJ sites were classified as high, medium, and low, respectively. The survival rate and specific growth rate were significantly greater for abalones cultured at sites DS and JJ than site LJ (p < 0.05), while the collagen content and the muscle parameters hardness, cohesiveness, chewiness, resilience, and shearing force were significantly higher at site LJ than sites DS and JJ (p < 0.05). Non-targeted metabolomics analyses of JJ vs. DS, JJ vs. LJ, and LJ vs. DS identified 124, 77, and 121 significantly different metabolites under the positive ion mode, and 68, 49, and 62 under the negative ion mode, respectively. Signaling pathways related to amino acid synthesis and metabolism were identified. Phenylalanine, glutamic acid, and histidine were confirmed as differential metabolic markers. Targeted metabolomics identified five "delicious amino acids" (glycine, aspartate, phenylalanine, tyrosine, and alanine), which had significantly higher contents in abalones cultured at site LJ than sites DS and JJ. Correlation analysis demonstrated that aspartate and phenylalanine were positively correlated to cohesiveness, chewiness, hardness, and shearing force, while negatively correlated to total protein content. These results provide theoretical references for cultivation of high-quality products and sustainable development of the abalone aquaculture industry.