The effect of sublethal concentrations of zinc on growth and plasma glucose levels in rainbow trout, Salmo gairdneri (Richardson).

The long term effects of three sublethal concentrations of zinc (0.214, 0.52 and 1.12 ppm) on growth and plasma glucose concentration in yearling rainbow trout Salmo gairdneri (Richardson) were investigated. Analysis of covariance of percent weight increase revealed that a significant inhibition of growth (P less than 0.05) in the 1.12 ppm zinc-exposed fish had occurred. Plasma glucose showed a significant hyperglycemia (P less than 0.05) in all three zinc-exposed groups of fish after 7 days exposure and in the 1.12 ppm zinc-exposed group after 63 days. The hyperglycemia observed has been explained as possibly resulting from activation of the pituitary-interrenal axis by the stress of zinc causing mobilization of tissue glycogen.