Hormonal, morphological, and physiological responses of yellow perch (perca flavescens) to chronic environmental metal exposures

The effects of a chronic environmental exposure to metals on the hormonal, physiological, and reproductive status were assessed in yellow perch (Perca flavescens) sampled in six lakes situated along a contamination gradient of Cd, Zn, Cu, Pb, and Ni in the mining region of Rouyn-Noranda, Québec. Fish were captured in the summer and fall, and sampled before or after a confinement of one hour. Metal concentrations in the kidneys and the interrenal tissues (homologous to mammalian adrenals) were measured to compare tissue-specific metal accumulation. An exposure-related decrease of condition factor, gonadosomatic index (GSI), branchial Na⁺/K⁺-ATPase activity, plasma thyroxine (T4), trüodothyronine (T3), and 17β-estradiol and an impaired capacity to enhance cortisol levels after confinement were observed. Fish from the metal-contaminated lakes possessed gonads at less mature stages and exhibited structural alterations of their gills, interrenal cells, and thyroid follicle epithelium. A comparison of the morphological, biochemical, and physiological endpoints measured in the present study revealed that plasma concentrations of hormones and parameters of gill function were the most affected by metal contamination. The results of this study indicate that lifelong exposures to sublethal concentrations of metals alter the physiological functions of fish and delay reproduction.