The effect of CO2, total ammonia nitrogen and pH on growth of juvenile lumpfish (Cyclopterus lumpus).

The objective of this study was to examine the effects of CO 2 , total ammonia nitrogen (TAN: nitrogen bound as either NH 3 or NH 4 +) and pH on the growth and survival of juvenile lumpfish in a two-month growth study. The results demonstrate the complex interactions of these water quality variables. The specific growth rate (SGR) of the lumpfish was progressively reduced with increasing [CO 2 ] concentration above 5–10 mg·L−1. However, growth may be reduced at even lower [CO 2 ] and the results provide no clear safe limits under which the growth of lumpfish is unaffected by CO 2 concentration. At the lowest [CO 2 ] tested (8 mg·L−1) the SGR was reduced compared with controls. Moreover, in treatments where the [CO 2 ] concentration increased to 8 mg·L−1 as pH was artificially reduced, the SGR was similarly reduced. These results indicate that lumpfish juveniles are very sensitive to increased [CO 2 ] concentration in water. The SGR of the lumpfish was progressively reduced as the NH 4 + concentration increased while maintaining the [NH 3 ] constant (70–80 μg·l−1). However, in these treatments the [CO 2 ] also increased to 8–10 mg·L−1 due to changes in pH and this likely contributed to reduced growth. Moreover, due to nitrification in the rearing systems, the nitrite concentration also increased to critical levels (1.5–4.2 mg·L−1) that could affect growth. Therefore, the results do not provide clear evidence for effects of increased NH 4 + on the growth of lumpfish. Taken together, the results of the experiments show that lumpfish are sensitive to perturbations in water quality and provide a benchmark for operational welfare indicators in lumpfish aquaculture. • The effects of CO 2 , total ammonia nitrogen (TAN) and pH on the growth and survival of lumpfish was studied. • pH in the range 7.2–7.8 does not directly affect the growth of lumpfish. • Growth is reduced at CO 2 concentration from 8 mg·l−1. • NH 3 at relatively low concentrations (0.08 mg·l−1) has negative effect on lumpfish growth. • Lumpfish are sensitive to perturbations in water quality. [ABSTRACT FROM AUTHOR]