Midwest Fish & Wildlife Conference 2018

AUTHORS: Aaron O’Connell, Wisconsin Department of Natural Resources & U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, Univ. of Wisconsin-Stevens Point; Ryan Koenigs*, Wisconsin Department of Natural Resources; Daniel Isermann, U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, Univ. of Wisconsin-Stevens Point; Ron Bruch, Wisconsin Department of Natural Resources (Retired); Steven Campana. University of Iceland

ABSTRACT: Pectoral spines have been the preferred calcified structure used for estimating age of Lake Sturgeon (Acipenser fulvescens), as well as other sturgeon species. However, age estimates from pectoral fin spines can underestimate the age of Lake Sturgeon = age 14. Age interpretations from otoliths were reported as valid for Lake Sturgeon, but difficulties in otolith availability, collection, and processing have resulted in little to no comprehensive work with Lake Sturgeon otoliths. We will evaluate four different techniques for estimating age and growth rates of Lake Sturgeon including: use of sectioned pectoral fin spines, application of a correction factor assigned to ages estimated from pectoral fin spines, otolith cross sections, and a Fabens– Wang growth model based on recaptures of PIT tagged fish. Pectoral fin spine and otolith age estimates from known-age Lake Sturgeon (ages 4-15) will be used to re-assess accuracy of age estimates for juvenile fish, while a broader suite of methods will be applied to age and growth data collected from older fish. Recent experimentation with otoliths using a thicker cross section followed by sanding and polishing has yielded promising results in terms of accuracy.