Effects of the prophylactic use of Romet®-30 and copper sulfate on growth, condition and feeding indices in Channel catfish (Ictalurus punctatus)

The effects of the prophylactic use of Romet®-30 and copper sulfate on catfish growth were assessed. Healthy channel catfish (Ictalurus punctatus) juveniles were exposed to Romet®-30 and copper sulfate during a period of 11 weeks; Romet®-30-treated fish received a therapeutic dose in the feed, while copper sulfate-treated fish were exposed to the chemical twice a week for 1 h. Body weight and length, specific growth rate, condition index, feed intake, and feed conversion index were assessed weekly. Both Romet®-30 and copper sulfate had a significant suppressive effect on channel catfish growth (weight and length): control fish were 12% heavier and 4% larger than Romet®-30-treated fish, and 30% heavier and 10% larger than fish treated with copper sulfate. Specific growth rate (SGR, %/day) was consistently lower in treated fish; however, significant differences (P < 0.05) were only observed during the interval of 8−11 weeks. Appetite was not suppressed, and is not the mechanism behind the inhibition on growth observed, which is more likely due to a decrease in feed conversion index. The present study indicates that, at concentrations commonly used in aquaculture, prophylactic, intermittent exposure of healthy channel catfish to copper sulfate or Romet®-30 induce growth suppression and should be used with caution.