Accumulation of Cadmium by Rainbow Trout, Salmo gairdneri, during Extended Exposure

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Abstract
Adult rainbow trout, Salmo gairdneri, were exposed to 3.6 and 6.4 .mu.g Cd/L for 178 d. Cadmium accumulated most rapidly in gill tissue which became saturated at levels 100-fold higher than controls within 24 and 52 d in the high- and low-metal exposures, respectively. Liver cadmium increased 250- to 400-fold over the test period but accumulation exhibited a plateau between 52 and 129 d followed by a rapid rise by 178 d. Kidney cadmium increased consistently throughout the test period to levels approximately 50- to 100-fold higher than control values. Cadmium in the gut and skin increased 10- and 5-fold, respectively, while no increase was recorded in white muscle. A maximum of 2.1% of the cadmium available in a commerical diet (0.2 .mu.g Cd/g dry food) was accumulated in control fish. Although cadmium was not detected in the urine, urinary zinc excretion was elevated in trout exposed to 6.4 .mu.g Cd/L such that 7 mol of zinc was excreted per 1 mol of cadmium accumulated during the initial 24 d of exposure. The whole-body burden of cadmium increased linearly with time in both treatments with a time constant of 0.366 and 0.554%/d for trout exposed to 3.6 and 6.4 .mu.g Cd/L, respectively.