COMPARISON OF MERCURY CONCENTRATIONS IN LIVER, MUSCLE, WHOLE BODIES, AND COMPOSITES OF FISH FROM THE RED-RIVER OF THE NORTH

Carp (Cyprinus carpio) from four sites and channel catfish (Ictalurus punctatus) from one site in the Red River of the North in 1994 were an alyzed for total mercury content. In carp, mercury concentrations diff ered among liver, muscle, and whole bodies (0.11, 0.31, and 0.18 mu g/ g wet weight, respectively), between large and small size groups, but not location. Mercury distribution in channel catfish tissues differed from that in carp. Liver and muscle tissue had similar mean concentra tions; each was higher than whole-body concentrations (0.16, 0.18, and 0.11 mu g/g, respectively). Mercury concentrations were not significa ntly different between the two size groups of channel catfish. Weighte d-mean mercury concentrations from seven individual fish agreed closel y (usually within 10%) with concentrations determined on physical comp osites of the same fish. The ratio of mercury in whole bodies to mercu ry in muscle was similar for both carp and channel catfish. Historical data indicate that this ratio may be applicable to other species and locations. The ratio of mercury in livers to whole bodies and muscle d iffered between carp and channel catfish, which may reflect physiologi cal differences between different trophic groups.