Relative recruitment success of stocked age-1 vs age-0 lake sturgeon (Acipenser fulvescens Rafinesque, 1817) in the Nelson River, northern Canada

Abstract

Summary Success of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) stocking programmes has rarely been evaluated. As of the early 1990s, Lake Sturgeon populations were nearly extirpated from several sections of the upper Nelson River, Manitoba, at least in part due to historical overexploitation. Between 1994 and 2011, 20 885 fingerlings (age-0, untagged) and 1117 yearlings (age-1, 1014 PIT tagged) were stocked into an upper Nelson River reach. In fall 2012, a Lake Sturgeon population inventory using gill nets assessed post-release survival/retention of stocked fish. Of 91 unique Lake Sturgeon captured, 67 (74%) possessed PIT tags, signifying they were stocked at age-1. Relative recruitment success was conservatively estimated to be 17.7 times greater for age-1 vs age-0 stocked fish based only on PIT tag recapture data. However, including 19 additional fish identified as stocked at age-1 based on atypical ‘first’ annuli patterns, the revised relative recruitment success rate was 130 times greater for age-1 vs age-0. An interpreted consensus ageing method produced correct age assignment 97% of the time for juveniles of known age, despite complications caused by overwinter growth in the hatchery.