Seasonal variations and alterations of sex steroid levels during the reproductive cycle of male roach (Rutilus rutilus).

Seasonal variations of plasma steroid concentrations i.e. progesterone (P), 11-ketotestosterone (11-KT) and 17-β-estradiol (E2) were determined immunoenzymatically during a whole reproductive cycle in male roach (Rutilus rutilus) caught in a reference site. Plasma 11-KT concentrations were significantly correlated with gonad growth, expressed as the gonado-somatic index (R² =0.60; p<0.05) and highest concentrations (757 ± 99 pg ml⁻¹ ) coincided with the final testis maturation in March. E2 and P concentrations peaked once during the reproductive cycle. E2 synthesis was significantly induced during the spawning period while P concentration peaked at the very start of the gametogenesis (June) thus suggesting specific roles of these steroids in the reproductive cycle. Comparison of reference levels were then made with plasma steroid concentrations from male roach sampled in polluted areas in the North of France. A significant decrease of E2 (50-60%) and 11-KT (76-84%) was measured, indicating that endocrine disrupting compounds may have interfered with the normal sex steroid synthesis. Contrary to the E2 and 11-KT sex steroids, plasma P concentration was not significantly affected in fish inhabiting impacted areas.