Determining the Relationship Between Water Quality and Ulcerative Mycosis in Atlantic Menhaden

Abstract

The objectives of this study were to investigate the possible causes of ulcerative mycosis (UM) in the Albemarle-Pamlico Estuary. Ulcerative mycosis is the commonest disease affecting the finfish populations of the Albemarle-Pamlico Estuary. While infectious agents have been isolated from UM lesions, the underlying environmental cause of the disease remains a mystery. We presently know very little of how water quality (including pollution) influences UM prevalence. The difficulty in reproducing the disease by simply challenging fish with the fungal pathogen suggests that environmental stress may play a very important role in disease development.

Previous sampling surveys for UM that simultaneously examined water quality did not always show any consistent relationship to disease prevalence, perhaps because water quality monitored simultaneously with disease sampling may not be representative of the actual conditions that caused the disease outbreak.

To obtain more reliable data on the risk factors influencing the development of UM, we placed clinically normal Atlantic menhaden in tanks at various sites along the Albemarle-Pamlico Estuary and examined them periodically for the development of UM lesions. We also simultaneously measured ambient water quality, including dissolved oxygen, salinity, temperature, pH, ammonia, nitrite, chlorophyll a, and prevalence of a new toxic dinoflagellate that we have recently discovered in the Albemarle Pamlico Estuary.