The "low-intensity" management practices used prior to the 1980's generally resulted in good pond water quality and lower overall stress on fish populations. Lower fish densities also meant less efficient transmission of disease organisms. Over the years, stocking and feeding rates steadily increased and producers adopted a multiple-batch cropping system wherein new populations of fingerlings were stocked into ponds with existing populations of larger fish. These production practices lead to the emergence of infectious diseases as the primary limiting factor in catfish production, and disease outbreaks are not uncommon even on well-run facilities.