Growth and Oxidative Stress of Clownfish Amphiprion ocellaris Reared at Different Salinities

Aquaculture of ornamental marine fish is often conducted in recirculating aquaculture systems (RAS) using artificial seawater. Considering the cost of salts to produce artificial seawater (salinity 35 parts per thousand), we investigated the effect of different salinities (5, 15, 25, and 35 parts per thousand) on survival, growth, and oxidative stress responses of juvenile clownfish Amphiprion ocellaris. All fish died when reared at salinity 5 parts per thousand, but at all other salinities survival was >= 95% in the other treatment groups. There was no influence of salinity on growth and oxidative stress responses of clownfish reared at salinities 15, 25, and 35 parts per thousand, except for the activity of glutathione S-transferase (GST) of fish reared at 25 parts per thousand, which was significantly lower compared to those reared in salinity 35 parts per thousand. The salinity of home aquariums is usually 35 parts per thousand, so even though clownfish can be reared in brackish water, they need to be transferred to full strength seawater (35 parts per thousand) in order to be commercialized. Therefore, we also evaluated the responses of acute transference of fish reared at 15 to salinity 35 parts per thousand. There were no mortalities associated with acute salinity transference and no oxidative damage was observed either. The total capacity against peroxyl radicals (ACAP) was immediately increased after fish were placed in salinity 35 parts per thousand, and remained high after 168 h (7 days), helping fish to deal with oxidative threats. In conclusion, it is possible to rear juvenile clownfish at 15 parts per thousand without harming growth or inducing oxidative stress, possibly reducing costs of water salinization. They can be transferred from brackish water to salinity 35 parts per thousand immediately before going to the retail market, with no mortality or oxidative damage.