A telephone survey of eel fishermen regarding external lesions and mortalities of American eels (Anguilla rostrata) from Lake Ontario and the St. Lawrence River basin, Canada.
Signs of decreasing landings and recruitment have been observed during the last decade in American eels (Anguilla rostrata) from the St. Lawrence River basin, Canada. A study was undertaken to examine whether important manifestational diseases among commercial catches could be associated with these declines. During this survey, 56 fishermen from Lakes Ontario, Saint-François and Saint-Pierre, the Richelieu River, the Québec City area and the St. Lawrence Estuary were interviewed. Most fishermen from every area reported decreasing catches since the 1980s. Eel mortalities were reported from 1990 to 1992 in Lake Saint-François, Lake Saint-Pierre and the Québec City area, but in apparently lower magnitude than in the past decades. The lesions observed on dead eels in Lake Saint-François indicated that the cause of the mortalities might be associated with the upstream hydroelectric dam. Eels with 'scratches all over the body' were only observed in the St. Lawrence Estuary. Fishermen from almost every area reported that they had observed eels with 'crooked tail', 'humpback' and 'cut tail' in low frequency in 1992. The questionnaire data were validated by comparing some of the results of the questionnaire survey and a processing plant survey in 1992. The use of questionnaires for assessing fish diseases in commercial species is discussed. The results of this survey do not indicate that the health of the American eels from the St. Lawrence River basin is severely impaired. However, the magnitude of diseases and mortalities was probably underestimated.
Pathogenesis of skin and liver neoplasms in white suckers from industrially polluted areas in Lake Ontario.
Increased prevalences of epidermal and hepatobiliary neoplasms in white suckers (Catostomu commersoni) and brown bullheads (Ictalurus nebulosus) in the Western region of Lake Ontario have been associated with industrial pollution, but the identity and causative role of environmental carcinogens have not yet been established. Most epidermal tumors of lip and body skin are benign focal proliferations that occur in fish from the polluted Hamilton region, and also in fish from less polluted sites in the Great Lakes. These skin tumors in white suckers do not have consistent alterations in cellular glutathione S-transferases (GST), suggesting that growth of skin tumors is not promoted by chemicals normally detoxified by GST. However, elevated levels of glutathione peroxidase (GPO) and glutathione reductase (GR) in skin papillomas are indicative of promotional peroxidative tissue injury, either caused directly by xenobiotics or indirectly by chemical-induced inflammation. Liver tumors in white suckers from Lake Ontario include preneoplastic, benign, and malignant populations of hepatocellular and biliary cells, all of which are more prevalent in fish from polluted sites. These liver tumors are consistently associated with chronic cholangiohepatitis and segmental cholangiofibrosis, but these conditions also occur in white suckers in non-industrial locations. Thus, the natural occurrence of biliary disease, not attributable to industrial pollution, may have some influence on the development of liver tumors. Some preneoplastic lesions and the majority of neoplastic hepatocellular and biliary lesions in white suckers have low levels of total GST, indicating that these liver neoplasms are not promoted by xenobiotics normally detoxified by hepatic GSTs.(ABSTRACT TRUNCATED AT 250 WORDS)
Ultrastructure of Malpighian and inflammatory cells in epidermal papilloma of white suckers Catostomus commersoni
Epidermal papillomas affect many white suckers Catostomus commersonj in the Great Lakes of North America, in particular among populations inhabiting polluted environments. Representative papillomas were examined ultrastructurally for viruses, inflammatory cell infiltrates and malpighian cell morphology. Three distinctive gross morphologies of papillomas all contained malpighian cell hyperplasia with some papilloma formation. Lip papillomas had normal malpighian cells but intercellular spaces were enlarged, desmosomes were aggregated, and increased numbers of all leukocytes, but particularly neutrophils, were evident. Discrete papillomas on the body surface contained normal malpighian cells with no aggregation of desmosomes, but enlarged intercellular spaces were filled with granular debris and a prominent neutrophil infiltrate was common. Diffuse papillomas (plaques) on the body surface contained malipighian cells with aggregated desmosomes. Lymphocytes and neutrophils were extremely abundant. Abnormal desmosome aggregations could alter the growth characteristics of malpighian cells making up lip papillomas and plaques. Inflammatory and immunologic cell infiltrates observed in these papillomas could limit the growth or persistence of these neoplasms. No virus-like inclusions were identified in any preparations. The role of viruses in the epidermal papillomas affecting white suckers in polluted locations of the Great Lakes remains unresolved.