Mercury accumulation in and growth rate of rainbow trout, Salmo gairdneri, stocked in an eastern Oregon reservoir.

Mercury concentrations in lateral muscle tissue from rainbow trout (Salmo gairdneri) stocked in a mercury contaminated eastern Oregon reservoir increased linearly during the first five months that the fish were in the reservoir, followed by a leveling off period during which the mercury uptake curve became nearly asymptotic after eight months. In addition, the mean mercury concentrations present in three year classes of trout which had lived in the reservior for 7, 19, and 31 months, respectively, were not significantly different, indicating that the uptake curve remains nearly asymptotic indefinitely. The shape of the curve is believed to be a result of exchange equilibria between water and tissue and factors that influence fish metabolism. It is estimated that 0.05 microgram Hg/L of methylmercury in water would have accounted for all of the methylmercury accumulated by trout in the reservoir. Growth rates (mg/g per day) of trout in the reservoir ranged from 0.7 in December to 39.7 in April, resulting in food consumption rate estimates ranging from 25 to 140 mg/g per day.