Tissue-specific copper concentrations in red drum after long-term exposure to sublethal levelsof waterborne copper and a 21-day withdrawal

Juvenile Red Drum Sciaenops ocellatus were exposed to sublethal concentrations of waterborne copper (Cu; 0.25–0.35 mg/L) for 242 d using an ethanolamine chelated Cu compound as a prophylactic treatment to control ectoparasites in recirculating aquaculture systems. Skin, muscle, gill, liver, and intestine tissues were collected on days 1, 3, 5, 15, and 21 during the 21-d depuration. Liver and intestine tissues accumulated Cu at a rate that was strongly influenced by the environmental Cu load. Skin, gills, and muscle tissues did not accumulate substantial amounts of Cu despite its presence at therapeutic levels. The rank order of the Cu concentrations in the different tissues was as follows: intestine > liver > gills > skin > muscle. Predictive equations for tissue Cu concentrations (µg/g) relative to time of withdrawal (d) and waterborne Cu concentration (mg/L) were generated using trend analysis. The relationships between tissue Cu concentrations and time of withdrawal were significant, with all tissue Cu concentrations decreasing over time. The relationships between tissue Cu concentrations and waterborne Cu concentration were also significant, with elevated waterborne Cu concentrations resulting in higher tissue Cu concentrations, especially in the intestine, liver, and gill tissue samples. Red Drum cultured in recirculating aquaculture systems had lower (26–52-µg/g) detectable Cu concentrations in muscle tissue than wild-caught Red Drum (414 µg/g).