Effect of CO₂ on juvenile cod

The water in land-based fishfarms can be recirculated to conserve heat, reduce pumping costs and effluent discharge, and minimize the introduction of pathogens. When water is recirculated metabolic waste products such as CO₂ accumulate in the system and require removal. The biological effect concentration of CO₂ needs to be known to maintain fish health and correctly size CO₂ stripping units. We tested the tolerance of juvenile Atlantic cod to chronic exposure to elevated CO₂ in the range expected in a recirculating aquaculture system.

Juvenile cod (15 g) were grown in a recirculating system at 20‰ salinity and 10ºC for 55 days under three CO₂ regimes:

	Low CO₂	Medium CO₂	High CO₂
CO₂ mg/L	2	8	18
PCO₂ µatm	1000	3800	8500
PCO₂ mm Hg	0.6	2.8	6.3
pH	7.80	7.40	7.06

Gaseous CO₂ was added directly into each tank and monitored using OxyGuard CO₂ Analyzers. Weight gain, growth rate and condition factor were substantially reduced with increasing CO₂ dosage.

The size-specific growth trajectories of fish reared under the medium and high CO₂ treatments were approximately 2.5 and 7.5 times lower (respectively) than that of fish in the low treatment.

Size variance and mortality rate was not significantly different amongst treatments, indicating that there was no differential size mortality, and the CO₂ levels tested were within the adaptive capacity of the fish.

The CO₂ effect concentrations in our study were considerably lower than those reported for the few other studies that have tested the chronic effect of elevated CO₂ on marine fish. Reanalysis of the carbonate chemistry conditions reported in these other papers indicate that CO₂ concentration may have been overestimated in two of the three studies.

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This work was made possible by a postdoc fellowship from the NZ Foundation for Research Science and Technology and a Marie Curie Fellowship from the European Comission.

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This research has been published and is available as follows:

Moran, D., Støttrup, J.G. (2011). The effect of carbon dioxide on growth performance of juvenile Atlantic cod Gadus morhua L. Aquatic Toxicology 102, 24-30.

doi:10.1016/j.aquatox.2010.12.014 ------- get PDF of paper

Moran, D., Tubbs, L., Støttrup, J.G. (2012). Chronic CO2 exposure markedly increases the incidence of cataracts in juvenile Atlantic cod Gadus morhua L. Aquaculture 364, 212-216.

doi:dx.doi.org/10.1016/j.aquaculture.2012.08.044 ------- get PDF of paper

Effect of CO2 on juvenile cod

Effect of CO₂ on juvenile cod