Application of a Pair-Breeding Fathead Minnow (Pimephales promelas) Adult Reproduction Bioassay to a Pulp Mill Effluent

Abstract

Abstract A short-term reproductive bioassay was applied to observe performance of pair-breeding fathead minnow (Pimephales promelas) before and after exposure to treated pulp and paper mill effluent. Reproductive performance was assessed for 21 days under controlled laboratory conditions to obtain baseline data of endpoints including cumulative egg production, number of spawning events, hatching success, and occurrence of deformed larvae. Breeding pairs were then exposed to 50 and 100% concentrations of secondary treated effluent for an additional 21 days. A significant reduction in egg production after exposure to both 100 and 50% pulp mill effluent was observed. This was accompanied by an increased appearance of pathological lesions (eosinophilic material) in male gonads as well as increased gonad size (gonadosomatic index). Reduced hatching success and appearance of larval deformities were also observed after exposure to both 50 and 100% pulp mill effluent. The pattern of responses observed may indicate that the reduced reproductive output was due to exposure to endocrine disrupting compounds within the effluent. By using the short-term fathead minnow bioassay, we were able to identify a response pattern to pulp mill effluent that is indicative of exposure to estrogenic and/or androgenic compounds.