Verification of Age- At- Length and Growth Rates of Variegate Darters

Monday, September 9, 2013
Governor's Hall I (trade show) (Statehouse Convention Center)
Laura Heironimus , Natural Resource Management, South Dakota State University, Brookings, SD
Jane E. Argentina , Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA
Paul L. Angermeier , U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Polytechnic Institute and State University, Blacksburg, VA
Fish population dynamics are strongly influenced by variation in fecundity and mortality rates across different-aged individuals. For example, populations are more stable if breeding individuals come from multiple cohorts because overall fecundity is not reliant on the strength of a particular year-class. Understanding variation in fecundity and mortality is especially important for imperiled species, where population sizes may be small and predicting risk of extinction based on failed year-classes is important to wildlife managers. Age and growth rates of many stream fishes can be estimated from the distinct rings laid on otoliths during growth cessation periods, similar to tree-ring age analysis. We extracted otoliths from a wide size range of variegate darters Etheostoma variatum and estimated age- at- length and growth rates by year. We found variegate darters live up to seven years, three years older than previously thought based on less accurate aging techniques. We found rapid growth during the first two years, and large individuals (>80 mm standard length) were 4-7 years old. Aging fish from otoliths gave a larger range of age classes than previously suspected. This knowledge will help us understand population dynamics of variegate darters and will inform management of this imperiled stream fish.