Elimination of Hexachlorobenzene (HCB) by Rainbow Trout (Salmo gairdneri), and an Examination of its Kinetics in Lake Ontario Salmonids

Abstract

Subadult rainbow trout (S. gairdneri) were fed diets containing hexachlorobenzene (HCB [insecticide]) to establish mean body burdens of 225 and 440 .mu.g HCB/fish. They were sampled after 0, 24, 55 and 110 days to estimate the rate of elimination. The biological half-life [T1/2] of HCB for trout was at least 7 mo. and perhaps as long as several years. T1/2 was calculated using body burden or .mu.g HCB/fish, and tissue concentrations or .mu.g/kg HCB. Estimates of T1/2 derived from tissue concentrations ranged from 61-117 days but this was due to a relative increase in body weight. The implications of increasing body weight on kinetics measurements were discussed and an equation was presented that adjusted for changes in body weight where estimates of T1/2 were calculated using tissue concentrations. The results were used to examine the kinetics of HCB in salmonids collected from Lake Ontario. Using the information derived from laboratory studies on rainbow trout, good agreement was achieved between expected level and that monitored in field samples of rainbow trout, but only a fair agreement was suggested for lake trout (Salvelinus namaycush) and coho salmon (Oncorhynchus kisutch). Differences in the HCB kinetics of these species may be attributed to body weight, age and feeding habits. Concentrations of HCB reported in field sampling programs generally ranged from 1-100 .mu.g/kg fish and these levels were primarily due to the limited availability of HCB in the Lake Ontario environment.