A processing plant survey of external lesions of American eels ( Anguilla rostrata) from Lake Ontario and the St. Lawrence River, Canada

Abstract

Signs of decreasing landing and recruitment were observed in the last decade in American eels ( Anguilla rostrata) from the St. Lawrence River basin, Canada. In order to verify if the declines were associated with high prevalence of diseases among commercial catches, a total of 12243 eels captured in five commercial fishing sites were inspected at two processing plants in 1992. They were all examined for external lesions and palpated to detect vertebral deformities. Eels from Lakes Ontario, Saint-François and Saint-Pierre were mainly resident eels, while those from the Richelieu River and the St. Lawrence Estuary at Kamouraska were mainly mature migrating eels. Prevalences of every lesion observed were low (≤ 1%) at every site. Scratches all over the body were found only on eels from Kamouraska. Cutaneous ulcers were observed more frequently in the Richelieu River. Higher prevalences of vertebral deformities were found in mature migrating eels captured in Kamouraska and in the Richelieu River. Vertebral deformities were also observed more frequently among eels captured at the end of the 1992 fishing season in Kamouraska. Higher length, weight and/or age of mature migrating eels may be associated with higher prevalences of vertebral deformities among this group. These results do not indicate that the health of the American eels commercially captured in the St. Lawrence basin is severely impaired. However, the magnitude of diseases among the biological population is probably underestimated by such a survey.