Identification of a robust Lake Sturgeon (<i>Acipenser fulvescens </i>Rafinesque, 1917) population in Goulais Bay, Lake Superior

Abstract

Lake Sturgeon (Acipenser fulvescens Rafinesque, 1917) in Lake Superior are greatly depressed from their historic abundance, and few populations meet the rehabilitation goals identified by management agencies. A netting program targeting juvenile Lake Sturgeon (ages 3–15) was implemented from 2010 to 2012 in Goulais Bay, a shallow, productive bay in the south-eastern part of the lake, to determine abundance, distribution, population characteristics (size structure, condition, age structure, mortality and growth), and recruitment patterns. Five-hundred and thirty-one individuals were captured over the 3-year study, resulting in a mark-recapture estimate of 4977 (95% CIs 3295–7517) juveniles. Catch rates in this study were higher than in any other location in Lake Superior, with sturgeon being broadly distributed around the bay. Estimated annual survival rate ranged from 0.691 to 0.858, depending on the method used. The majority of fish captured were between 620 and 800 mm in total length and were between 4 and 10 years of age (range 1–29 years). Recruiting year-classes were apparent every year, with no apparent effects due to lampricide treatments (a suspected threat to age-0 Lake Sturgeon) in the Goulais River. Year-class strength was positively related to spring water levels. It is possible that this robust Goulais Bay population could help re-populate the south-eastern part of Lake Superior, which contains a number of large, productive embayment areas that formerly supported large Lake Sturgeon populations.