LIVER AND KIDNEY CONCENTRATIONS OF ZINC, COPPER AND CADMIUM IN CHANNEL CATFISH (ICTALURUS-PUNCTATUS) - VARIATIONS DUE TO SIZE, SEASON AND HEALTH-STATUS

Significant differences in liver and kidney concentrations of zinc (Zn ), copper (Cu) and cadmium (Cd) were detected in normal Mississippi fa rm-raised channel catfish (Ictalurus punctatus) collected at different times of the year. These seasonal differences were not solely due to variation in fish size. Comparing the concentration of each metal in l iver vs kidney indicated that Cd was lower in liver for all seasons st udied, Cu was higher in liver for all seasons studied, and Zn was high er in the liver in the winter-killed (winter mortality syndrome) and t he spring fish groups. Metal concentration was associated with body we ight, as indicated by significant Pearson correlation coefficients for kidney Cd (all seasons and fall), liver Cu (summer), liver Zn (all se asons and winter), and kidney Zn (all seasons and winter). The adjuste d means were not dramatically changed as compared to the raw data. Dif ferences were noted when seasonal values obtained from normal fish wer e compared to tissues of moribund fish afflicted with winter mortality syndrome. Zinc was reduced in liver and kidney of these moribund fish .