Quality of Effluents from Channel Catfish Hatcheries in Northwestern Mississippi

Abstract

AbstractSamples of water supply and effluent were collected from five commercial hatcheries for channel catfish Ictalurus punctatus in northwestern Mississippi. Hatcheries were visited three times at 2‐week intervals during the peak of the catfish spawning season. Samples were analyzed for total suspended solids, soluble and total phosphorus, total ammonia, total nitrogen, and 5‐d biochemical oxygen demand (BOD5). Net pollutant loads (effluent concentration minus inflow concentration) were low for all variables. Maximum average net loadings were 10.7 mg/L for total suspended solids, 0.13 mg/L for total phosphorus, 0.28 mg/L for total nitrogen, and 2.07 mg/L for BOD5. Because net pollutant loadings were low and groundwater supplies initially had low concentrations of solids and organic matter, effluents were of excellent quality with respect to those variables. Four of the groundwater supplies contained substantial background levels of phosphorus or nitrogen; accordingly, effluents from those hatcheries had moderate levels of those substances. The highest average effluent concentrations (ranges for all samples in parentheses) were as follows: total suspended solids, 12.3 mg/L (7‐ 19 mg/L); soluble reactive phosphorus, 0.36 mg/L (0.007–0.390 mg/L); total phosphorus, 0.45 mg/L (0.15‐ 0.53 mg/L); total ammonia nitrogen, 0.49 mg/L (0.13‐ 0.57 mg/L); total nitrogen, 0.60 mg/L (0.19–0.72 mg/ L); and BOD5, 3.03 mg/L (0.85–4.03 mg/L). These concentrations are lower than the corresponding concentrations in most potential effluent‐receiving streams in northwestern Mississippi, and total effluent volume from catfish hatcheries constitutes less than 0.02% of total annual streamflow in the region. It is therefore unlikely that catfish hatchery effluents will have a negative effect on receiving stream water quality.