Effects of salinities on the growth performance, muscle's flavor and transcriptomic responses in yellowfin seabream (Acanthopagrus latus)

Yellowfin seabream ( Acanthopagrus latus ) is a euryhaline fish species of significant economic importance, and salinity, as one of important ecological factors, widely affects its growth, metabolism, and flesh quality of the fish. Current study was conducted to investigate the growth performance, muscle's flavor and transcriptomic responses of A. latus (8.25 ± 1.85 g) cultured in different salinities (6, 13, 20, 27 and 34 psμ). At the end of the 12-week culture trials, the final size, weight gain and specific growth rate (SGR) of A. latus were significantly impacted by salinity, with the highest SGR at 20 psμ ( P < 0.05) and lowest at 34 psμ. The contents of polyunsaturated fatty acid (PUFA) (including eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA) and linoleic acid in at 6 psμ were significantly higher than those at any other salinity ( P < 0.05). The total content of volatile compounds in flesh was the highest in 20 psμ, of which there were more abundant aldehydes and ketones. Transcriptomic analysis identified differentially expressed genes (DEGs) between the 20 psμ and 34 psμ, with 161 genes up-regulated and 86 genes down-regulated in the 20 psμ. These DEGs were associated with muscle growth and development, amino acid metabolism, carbohydrate metabolism, and others. The reliability of transcriptome data was validated using qRT-PCR based on ten selected growth-related genes, which showed the same trends as the RNA-seq results. From the overall results of this study, we infer the growth performance and flavor can be significantly improved at the salinity of 20 psμ, and the fatty acid composition can be significantly improved at the salinity of 6 psμ for yellowfin seabream.