Midwest Fish & Wildlife Conference 2016

AUTHORS: Michael J. Hansen*, USGS Hammond Bay Biological Station; Nancy A. Nate, Michigan State University

ABSTRACT: Fishery research and management rely on reliable age and growth information to estimate growth and survival, and to evaluate how populations respond to management actions. This keynote address introduces key subjects related to the science of fish age and growth, including: preparation of calcified structures; interpretation of prepared structures; techniques to deal with bias in age estimation (quality control, accuracy, and precision); development of age and growth programs; age estimation of novel species; tools to analyze and interpret age data; and use of age data to develop growth models and inform management of fish populations. We first address why age and growth information is important for fishery management, and how biased age and growth estimates lead to misdiagnosis of fish stock health and resulting management prescriptions. We then review basic principles of age and growth estimation. Next, we illustrate how size-selective sampling, a common feature of fishery assessment programs, induces bias in age and growth estimates. Next, we review how sub-sampling strategies can be implemented to maximize usefulness of age and growth estimates, while simultaneously minimizing sub-sampling bias. Last, we review how to address accuracy and precision of age-estimation programs as a quality assurance system for any age estimation program. We conclude with a review of major issues that continue to challenge accurate and precise estimation of fish age and growth.