Abstract
This study evaluated the effects of bleached and unbleached kraft mill effluent on reproductive success of largemouth bass (Micropterus salmoides). Bass were exposed to effluent concentrations (0, 10, 20, 40, or 80%) for 28 and 56 d. Parameters measured included hepatosomatic index (HSI) and gonadosomatic index (GSI) and plasma concentrations of 17β‐estradiol (E~2~), 11‐ketotestosterone (11‐KT), and vitellogenin (VTG). At the end of the 56‐d period, bass were moved to hatchery ponds to evaluate spawning success. Spawning mats with eggs either were brought indoors for evaluation of fecundities, hatchabilities, and egg and fry size (measured at age 3 d), or were left in ponds and fry number and size recorded (average age of 14 d). Effluent exposure was verified by measuring resin acids (isopimaric, abietic, and dehydroabietic acids) in bile. Compared to controls, exposed bass had greater concentrations of resin acids in bile. In general, exposed females had lower concentrations of E~2~ and VTG (≥20% effluent), whereas males had lower concentrations of 11‐KT (≥20% effluent) and increased E~2~ (≥20% effluent). The HSI values increased in females (≥10% effluent), and GSI values decreased in both sexes (≥40% effluent). Fecundity, egg size, and hatchability did not differ across treatments, but an increase in the frequency of fry abnormalities and a decrease in fry weights was observed at effluent exposures of 40% and higher. However, results from the pond study, revealed a significant reduction in fry growth and survival (≥10%). This decline may have been caused by an increased frequency of deformities, in conjunction with alterations of growth. These changes could have resulted from alterations in egg quality because of failure of parental reproductive systems, from acute embryo toxicity after translocation of contaminants from the mother to the developing embryo, or from both.