Uptake, elimination and tissue distribution of dietary and aqueous cadmium by rainbow trout (salmo gairdneri richardson) and lake whitefish (coregonus clupeaformis mitchill)

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Abstract
Rainbow trout (Salmo gairdneri) and lake whitefish (Coregonus clupeaformis) were exposed for 72 d to 109Cd in pelletized commercial trout food or in the water in a continuous‐flow water exposure system. Blood, gill, gut, liver, kidney, muscle, skin, feces and gut contents were sampled from 40 fish in each group during the exposure phase and from 20 fish in each group during the subsequent 56‐d depuration period. Gill accumulated the highest cadmium concentrations. After 56 d of depuration, most of the cadmium in food‐exposed fish of both species was in the kidney, gut and liver, but water‐exposed fish retained most of the cadmium in gill and kidney. Whole‐body concentration factors (L/kg wet weight tissue) after 72 d of exposure for water‐exposed fish were 55 for rainbow trout and 42 for whitefish. Whole‐body bioconcentration factors after 72 d of exposure for food‐exposed fish were less than 1 (kg food/kg dry weight tissue). Both species accumulated significantly greater proportions of the cadmium dose from food than from water. The percentages of the cadmium dose accumulated after 72 d of water exposure were 0.15% for trout and 0.11% for whitefish, while for food exposure the values were 1.03% for trout and 1.01% for whitefish. A simple two‐compartment kinetic model was fitted to the data. Equilibrium cadmium bioconcentration factors for aqueous exposure were estimated to be 161 for rainbow trout and 51 for lake whitefish. Biological half‐times for depuration ranged from 24 to 63 d.