Effects of elevated carbon dioxide on the growth and welfare of Juvenile tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid

Increasing carbon dioxide (CO2) in the ocean are predicted to affect vital physiological functions and possibly reduce growth of marine fish. Yet, studies on the impacts on marine fish with the increasing CO2 is still limited. Therefore, this study aimed to explore the elevated CO2 effect on the growth and welfare (condition factor, blood parameters, stress analysis, gill histology) of newly developed commercially important marine fish, tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid or TGGG. TGGG juveniles were exposed for 120 days in a laboratory condition of CO2 groups: 390 μatm (control-current CO2), 610 μatm (moderate) and 1010 μatm (high) consistent with projections for CO2 concentrations in the ocean over the next 50–100 years. The experiments were done in triplicate (20 fish/tank; N = 180, total length = 20.0 ± 0.5 cm, weight = 94.0 ± 3.0 g). Results showed that the lowest specific growth rate (SGR) (0.65 ± 0.05% day−1) and condition factor (1.12 ± 0.01) were observed in high CO2. Unfavourable blood haematological and biochemical parameters were observed in high CO2 group. The highest stress level measured by glucose (102 ± 8 mg dL−1) and cortisol concentration (1.0 ± 0.1 ng mL−1) were also observed in the high CO2. Gill lesions were histologically observed in high CO2 treatment. The results suggested that high CO2 negatively affected the growth and welfare of TGGG. Outputs of this study would offers a simple tool to evaluate the potential risk of elevated CO2 to an important commercial marine grouper.