A biomonitoring approach to aquaculture effluent characterization in channel catfish fingerling production

The channel catfish (Ictalurus punctatus) industry has come under increased scrutiny because of potential environmental impact from their discharge. Physicochemical analyses have been used to characterize these effluents and their potential environmental impacts. In this study, the relationship between physicochemical characterization and bioassessment was examined for effluents from 12 commercial channel catfish fingerling ponds, sampled September 1999 through August 2001. On each sampling date, effluent samples were collected by opening the drain valve for 1 h. Biomonitoring and physicochemical analyses were conducted on the sample collected immediately after opening the drain ("initial sample") and the final sample collected after 1 h ("final sample"). Greater incidence of toxicity responses measured as % of total tests was observed in standard test organism exposures in initial samples than in final samples of monitored hourly discharges. In acute 48-h static non-renewal tests, Pimephales promelas experienced 20.5% significant (P < 0.05) survival reductions in initial effluent exposures and only 2.6% in final effluent exposures from 39 tested effluents. Ceriodaphnia dubia survival in chronic 7-day static-renewal tests was significantly (P < 0.05) reduced in 12.8% of 39 initial effluent exposures while there were no significant responses in final effluent exposures. Likewise, reproductive responses of C dubia were also significantly (P < 0.05) reduced in 35.9% of initial exposures and 15.4% of final effluent exposures from 39 tested effluents. Biomonitoring of fingerling pond discharges was used to evaluate effluent quality by measuring standard organism responses. While reduced effluent quality was of relative short duration, as is typical of the industry, this multidimensional approach, utilizing biomonitoring, was used to identify risk posed by critical concentrations of whole effluents to receiving stream communities. (C) 2004 Elsevier B.V. All rights reserved.