Cooperative Fish and Wildlife Research Units Program: Wisconsin Fishery
Education, Research and Technical Assistance for Managing Our Natural Resources

Wisconsin Fishery Project

Evaluating methodologies for estimating age and growth of lake sturgeon

September 2017 - August 2019


Participating Agencies

  • Wisconsin Department of Natural Resources

Use of accurate age data is critical to effective fisheries management as age data are incorporated into population dynamics models to assess growth and mortality. Pectoral fin spines have been the preferred calcified structure used to estimate age of Lake Sturgeon due to their display of distinct, enumerable annuli and their non-lethal sampling. However, age estimates from pectoral fin spines typically underestimate the age of Lake Sturgeon >14 years of age (Bruch et al. 2009). Otoliths have been used to estimate sturgeon age, but sample collection requires the fish to be sacrificed and results have been variable. Bruch et al. (2009) validated age estimates derived from otoliths for Lake Sturgeon using bomb radio carbon dating, but results have been difficult to replicate. Application of other methods to evaluate age and growth through correction factors and mark recapture data have been limited, but a rich data set exists for Lake Sturgeon on the Winnebago System to evaluate these techniques. Our objective is to evaluate four different methodologies (otoliths, pectoral fin spines, corrected spines, and Fabens-Wang models) for assessing age and growth of Lake Sturgeon on the Winnebago System. Paired calcified structures (pectoral fin spines and otoliths) will be removed from known-age and non-known-age Lake Sturgeon harvested during the 2014-2019 spear fisheries. Structures will be processed and read by 3 or more readers to evaluate precision. Age estimates from each structure will be used to construct age bias plots to compare age estimates between structures and readers. We will also explore the feasibility of correction factors and modeling of mark-recapture data (Fabens [1965]-Wang [1998]) to estimate age and growth of Lake Sturgeon.