Etiologies, observations and reporting of estuarine finfish lesions

Lesions in estuarine finfish are associated with a variety of organisms inc luding parasites and bacterial, viral, and fungal infectious agents. In add ition, trauma, suboptimal water quality, and other abiotic stress factors m ay result in the loss of homeostasis. We have observed solitary ulcerative lesions on menhaden sampled from the Chesapeake Bay, Maryland, the Pamlico River, North Carolina, and the St. Johns River, Florida. Histologically, th e lesions demonstrated a marked chronic inflammatory infiltrate and granulo mas in response to fungal hyphae throughout large areas of exposed necrotic muscle. Gram-negative rod-shaped bacteria were also observed in the lesion s, a common finding in ulcers of aquatic organisms. Similar observations in menhaden and other species have been described previously in the literatur e as ulcerative mycosis, mycotic granulomatosis, red spot disease, and epiz ootic ulcerative syndrome. Despite the many different known causes of fish lesions, the popular press and the scientific literature have recently emph asized Pfiesteria in piscicida and other Pfiesteria-like dinoflagellates (a nd their bioactive compounds) as the primary causative agent for finfish le sions, particularly mycotic granulomatous ulcers in Atlantic menhaden. Whil e some laboratory data suggest that Pfiesteria may play a role in field-obs erved lesions, much more cause-and-effect evidence is needed to determine t he importance of other risk factors, both alone or and in combination with Pfiesteria. In order to better understand the etiology of lesion initiation and progression in estuarine finfish, accurate assessments of environmenta l conditions collected on appropriate temporal and spatial scales, and fish morphological indicators consistent with gross and histological pathologic terminology, should be used for reporting fish lesion observations and kil ls. Further, this outlook will help to avoid bias and may foster a broader perspective for examining the health of estuarine systems in general. (C) 2 000 Elsevier Science Ltd. All rights reserved.