Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2008
Publication Date: 1/1/2009
Citation: Mischke, C.C., Wise, D.J., Zimba, P.V. 2009. Impact of Copper Sulfate on Plankton in Channel Catfish Nursery Ponds. Journal of the World Aquaculture Society. 40:122-128. Interpretive Summary: There is interest in applying copper sulfate pentahydrate (CSP) to catfish ponds to prevent trematode infections and proliferative gill disease. Copper is an algaecide and may affect plankton populations. We evaluated the effects of copper sulfate in catfish nursery ponds on water quality and plankton populations. Treatments of 3 and 6 mg/L CSP increased algal concentrations but reduced desirable zooplankton groups. Populations of important zooplankton to catfish fry began to rebound 6-12 d after CSP treatment. If CSP is used to treat fry ponds, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to increase.
Technical Abstract: Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04-ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6–12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing.