Potamologica1 Effects of Fish Hatchery Discharge

Abstract
The ecological impact of fish hatchery wastes on periphyton production rates and oxygen balance were determined in the Jordan River from March through June, 1971 and 1972. The hatchery, located in the Jordan Valley utilizes two systems of tributary springs for its water supply. Until spring 1972 the hatchery had been discharging its untreated wastes into the Jordan River but during winter, 1971 and 1972 two settling basins were built to remove 80–95% of settleable solids from the wastewater. The Jordan Valley National Fish Hatchery discharged the approximate equivalent of 898 kg of elemental phosphorus and 4,170 kg of elemental nitrogen between July 1970 and June 1971, and 998 kg of phosphorus and 4,604 kg of nitrogen between July 1971 and June 1972. These quantities comprised approximately 28% and 5% of the annual load of phosphorus and nitrogen, respectively, in the Jordan River at the vicinity of the hatchery. Periphyton production rates increased exponentially during the study periods. Mean production rates were seven times greater below the outfall than at the control station above the discharge in 1971, and five times greater in 1972. Although periphyton production rates were increased below the outfalls, oxygen balance was not affected significantly by the hatchery effluent, either before or after installation of settling basins.

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