Growth of indicator bacteria in a flow-through aquaculture facility

A flow-through commercial catfish growout operation was found to have high levels of fecal coliforms (FC) in the discharge. Analyses by academic, commercial and regulatory agency laboratories were conducted through the system over a five month period in 1991 for various indicator bacteria groups as well as potential pathogens with highly variable results. Biochemical differentiation of FC showed most to have been Klebsiella pneumoniae, K. oxytoca, E. coli and Citrobacter freundii. During production many of the effluent FC levels exceeded state surface water criteria for contact and non-contact recreation of 200/100 ml. Generally, great diversity in results were shown between laboratories depending on their analytical specialty and whether they were responding to requests to show the FC populations to have been fecal in origin, or potential pathogens.