Impacts of Trout Culture Effluent on Water Quality and Biotic Communities in Virginia Headwater Streams

Abstract

Abstract Five Virginia trout farms were selected for examination of effluent impacts on downstream water quality, periphyton production, and composition of macroinvertebrate and fish communities during fall 1994 and summer 1995. Annual trout production and feeding rates varied from 18.5 to 59.5 thousand kilograms and 15.6 to 87.6 thousand kilograms, respectively, and were correlated with discharge. Substrate embeddedness increased significantly (P < 0.07) downstream at two farms, but settleable solid concentrations in effluent were always less than 0.1 mL/L. Total ammonia nitrogen, un-ionized ammonia nitrogen, and nitrite nitrogen levels increased significantly (P < 0.001) downstream but were well below recommended thresholds for lethal exposure for aquatic organisms. Dissolved oxygen levels were significantly reduced (P < 0.001) downstream at postfeeding and predawn hours but were typically greater than 7.0 mg/L. Effluent water temperatures, pH, nitrate nitrogen, and total phosphorus concentrations did n...