| Summary: | Fish are adversely affected by high carbon dioxide concentrations, hence data on their tolerance level are particularly crucial especially for intensive production methods such as flow through and recirculating aquaculture system (RAS) that can accumulate CO2. The current study assesses how CO2 affects Atlantic salmon yolk sac fry specifically on their growth in length and weight as well as survival. Yolk sac fry were subjected and grown in different concentrations of carbon dioxide 1.8, 1.9, 5.4, 9.6, 17.7, 29.3 and 60.0 CO2 mg/l which are also labelled as groups in a replicate for a period of 33 days. A flow through system was used in this study for growing fish. Two methods were to induce the production of carbon dioxide in the fish tanks. The first was the addition of carbon dioxide in tanks to increase the CO2 to the desired levels and the other was addition of diluted HCl to water in tank which makes water acidic and indirectly increased the CO2 levels except in the control 1.8mg/l tank that was not given any treatment with a pH range of 6.3 to 7.6 All other major water quality indicators fell within the range that would usually be considered as favorable for fish growth. In the study it was revealed that pH reduction of water increased the production of carbon dioxide. Fish tanks exposed to 33 days CO2 at concentration up to 60 mg/l experienced low mortality. The mean ultimate body weight and size in the control treatments 1.8 mg/l with a high pH and 1.9 mg/l with a low pH was significantly higher. For fish length, 1.8 mg/l with high pH was significantly higher to 17.7 mg/l, 29.3 mg/l and 60 mg/l but in terms of weight it was significantly higher to 29.3 mg/l and 60 mg/l. Also, for fish weight, 1.9 mg/l with a low pH was significantly higher to 17.7 mg/l, 29.3 mg/l and 60 mg/l but in terms of length, it was significantly higher to 29.3 mg/l and 60 mg/l. The growth of fish, considering weight gain and size were considerably impeded as carbon dioxide dosage was increased. No effects observed at 9.6 mg/l and ...
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