Biological characteristics of adult Atlantic sturgeon (Acipenser oxyrinchus ) in the St Lawrence River estuary and the effectiveness of management rules.

Summary In 1998, a 5-year research project was begun to address the lack of information on the life history of St Lawrence River Atlantic sturgeon (Acipenser oxyrinchus ), an important commercial species in Québec, Canada. Since 1994, restrictive fishing regulations have been progressively imposed regarding season, size limit, quota and gear in the commercial fishery in order to increase spawner escapement. In this study, gill net sampling permitted the catch of 209 sturgeon over a 3-year period; among the 184 fish released with spaghetti tags, 69 were equipped with ultrasonic transmitters. Reproductive males ranged in size from 137 to 190 cm fork length (FL), and in age from 16 to 26 years. Size range of reproductive and maturing females were, respectively, 190–200 cm and 167–199 cm FL. No ages were available for the females. Using telemetry data, it was estimated that the spawning interval could be at least 3 years or more for a large majority of males. In the research catch, 88% of the adults were over the maximum permitted size limit of 150 cm FL. Recapture of telemetered sturgeon by commercial fishers was 10%; 100% survival rate was observed after handling. Biological characteristics of this northern population, slow growth, first spawning at old age and the long spawning interval means many years of exposure to the fishery before and after first spawning. It is concluded that regulations about season, quota and gear are not sufficient in and of themselves to protect spawners against exploitation, but the obligation to release all sturgeon larger than 150 cm, together with the other measures, is an effective means to protect the adult segment of the population. [ABSTRACT FROM AUTHOR]