Effect of flow velocity on the growth, stress and immune responses of turbot (Scophthalmus maximus) in recirculating aquaculture systems

• Published in: Fish & shellfish immunology Vol. 86; pp. 1169 - 1176
• Main Authors: Li, Xian, Ji, Liqin, Wu, Lele, Gao, Xiaolong, Li, Xueqin, Li, Jun, Liu, Ying
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2019
• Subjects: Animals; Aquaculture - methods; bilirubin; body length; cathepsin D; feed intake; Flatfishes - growth & development; Flatfishes - immunology; Flow velocity; gene expression; Growth; immune response; Immunity, Innate; Innate immune responses; innate immunity; juveniles; lysozyme; protein content; rearing; recirculating aquaculture systems; Scophthalmus maximus; Skin - immunology; Stress, Physiological - physiology; superoxide dismutase; turbot; urea nitrogen; Water Movements; water quality; Scophthalmus maximus; Flow velocity; Innate immune responses; Growth
• ISSN: 1050-4648; 1095-9947; 1095-9947
• DOI: 10.1016/j.fsi.2018.12.066

Land-based recirculating aquaculture systems (RAS) are widely utilized for turbot (Scophthalmus maximus) culture. Flow velocity in the tank is essential to maintain water quality, conservation of energy and fish welfare. However, little is known about how turbot respond to different velocities in the long term. In this study, water quality was kept constant, allowing the effect of flow velocity on the feeding intake, growth, plasma biochemical indexes, innate (non-specific) immunity and immune-related stress gene expressions in the skin to be examined in isolation in RAS. Turbot (average body length 20.10 cm) were reared for 60 days in RAS under three velocities, 0.06 m s−1, 0.18 m s−1, and 0.36 m s−1, corresponding to approximately 0.3 body length per second (bl s−1), 0.9 bl s−1 and 1.8 bl s−1, respectively. The results showed that at velocities of 0.36 m s−1 (1.8 bl s−1), juvenile turbot were subject to stress accompanied by a reduced growth rate. A velocity of 0.36 m s−1 was also found to significantly reduce SOD and GSH activity, and the concentration of total protein in plasma, while concentrations of urea nitrogen (BUN) and total bilirubin (TBIL) increased. There was an up-regulation of cathepsin D and lysozyme (LZM) in the skin at the highest velocity, implying the activation of stress and immune responses. At the medium velocity of 0.18 m s−1 (0.9 bl s−1), turbot increased their feed intake, obtained an elevated special growth rate (SGR), and exhibited significantly higher AKP and ACP activity in plasma. Overall, the results suggest that excessively high velocities are a stressor for turbot inducing an immune response in the skin, which is sensitive to environmental changes. A velocity of approximately 0.9 bl s−1 is suggested to promote growth and obtain better innate immunity of cultured turbot. •This is the first study examining stress and immune responses in turbot at different flow velocities.•Moderate velocities were found to promote feed intake and growth performance of turbot.•High flow velocity was found to induce stress responses and oxidative damage.•An up-regulation of innate-immune related gene expression was detected in skin of turbot at the highest velocity.•An approximate velocity of 0.9 bl s−1 would improve the growth performance and innate immune of turbot.