Growth performance, body composition and metabolic rate of marine fish under different water pH levels and CO2 concentrations

Abstract

The growth performance, body composition and stress responses of olive flounder, Paralichthys olivaceus (50.8 g mean body weight) and dark-banded rockfish, Sebastes inermis (13.8 g) reared under three different water pH levels (8.0, 7.5 and 6.5 in P. olivaceus, and 8.0, 7.0 and 6.0 in S. inermis) were investigated. There were no significant differences in weight gain (WG), feedefficiency (FE), specific growth rate (SGR) and feed intake (FI) in P. olivaceus exposed to 8.0, 7.5 and 6.5 pH levels (P > 0.05). The lowest WG, FE, SGR and FI of S. inermis was observed at pH 6.0 (P < 0.05). Decrease in the pH level provoked significant (P < 0.05) increase of lipid and decrease of ash content in P. olivaceus, but the opposite phenomenon appeared in S. inermis. Hemoglobin (Hb) content of fish in pH 6.5 was significantly (P < 0.05) lower than those of fish inpH 8.0 and 7.5. Decrease in the pH level provoked significant (P < 0.05) increase of GOT, GPT, glucose and triglyceride concentration of blood in S. inermis. Although the histological changes of liver and kidney of P. olivaceus were not observed in all treatments, gill of fish at pH 6.5 was observed with some damaged.The effect of water temperature and CO2 concentration on metabolic rate of red seabream (Pagrus major), black rockfish (Sebastes schlegelii) and starry flounder(Platichthys stellatus) was investigated. The oxygen consumption rate (OCR) was measured under 6.5 in P. olivaceus, and 8.0, 7.0 and 6.0 in S. inermis) were investigated. There were no significant differences in weight gain (WG), feedefficiency (FE), specific growth rate (SGR) and feed intake (FI) in P. olivaceus exposed to 8.0, 7.5 and 6.5 pH levels (P > 0.05). The lowest WG, FE, SGR and FI of S. inermis was observed at pH 6.0 (P < 0.05). Decrease in the pH level provoked significant (P < 0.05) increase of lipid and decrease of ash content in P. olivaceus, but the opposite phenomenon appeared in S. inermis. Hemoglobin (Hb) content of fish in pH 6.5 was significantly (P < 0.05) lower than those of fish inpH 8.0 and 7.5. Decrease in the pH level provoked significant (P < 0.05) increase of GOT, GPT, glucose and triglyceride concentration of blood in S. inermis. Although the histological changes of liver and kidney of P. olivaceus were not observed in all treatments, gill of fish at pH 6.5 was observed with some damaged.The effect of water temperature and CO2 concentration on metabolic rate of red seabream (Pagrus major), black rockfish (Sebastes schlegelii) and starry flounder(Platichthys stellatus) was investigated. The oxygen consumption rate (OCR) was measured under