A population of Atlantic tomcod inhabits the brackish waters of the St. Lawrence River near Quebec City, Province of Quebec, Canada. Adults move into rivers near Trois-Rivieres City (primarily the Ste-Anne and Batiscan Rivers) during winter to spawn beneath the ice. Fishing is an important tourist activity for the neighboring town, Ste-Anne de la Perade, during spawning. In 1987-1988, the sport catch rate decreased dramatically from nine fish per hour, the rate observed in previous years, to one fish per hour. The Provincial Fish and Wildlife Department (MCLP) conducted a population evaluation by hoop net sampling the following season. Histopathological lesions were present in 16.7% of 232 fish from sampling conducted by MCLP officers during the winter of 1992-1993. The most frequent lesions included fin ray granulomas (3.9%), oral ulcerations with or without accompanying mandibular osteomyelitis (3.8%), cutaneous scars (3.6%), and ulcerations (2.8%). Bacteriological examination was performed on 124 fish with gross evidence of ulceration. Pseudomonas flourescens and Shewanella putrefaciens were the most frequent isolates (each bacteria was isolated from 18.5% of cultured fish).