Conservation Implications of Behaviour and Growth of the Lake Sturgeon, Acipenser fulvescens, in Northern Ontario

We investigated the age, growth and population structure of lake sturgeon in the Groundhog and Mattagami rivers, northern Ontario, Canada. Age, estimated from counts of annuli in pectoral fin rays, ranged from 1 to 69 years (y) in the 327 fish examined. Growth, expressed as an increase in fork length and calculated from a von Bertalanffy growth equation, slowed from a peak of about 3.9 cm year-1during the early juvenile period (<9 y) and approached an asymptote beyond 90 y (FL=141.549[−e-0.043(t−4.901)]). A length–mass equation (log M=3.07 log FL−2.26) and conversion factors for fork and total length (FL=0.97 TL−1.154) from our study ranged from 14.5 to 142 cm (fork length), 15.5 to 158 cm (total length) and 20 to 19 730 g (live mass) for 1177 individuals. We found no evidence for spawning or recruitment to the population in our study area. Population age and length structure were strongly bimodal, and growth rate appears to have slowed over the past decade. We discuss the possible environmental correlations and conservation implications of this age (size) distribution.