Midwest Fish & Wildlife Conference 2017

AUTHORS: Sydney E. Manning, Bryan S. Stevens, David M. Williams - Michigan State University Boone and Crockett Quantitative Wildlife Center

ABSTRACT: Stabilization of wild turkey (Meleagris gallopavo) populations and high demand for recreational harvest has made it desirable to understand performance of harvest management systems. Existing models assume harvests vary annually about some target level, but the precise relationship between regulations and realized harvest rates is not clear. Similarly, decisions are often made at multi-year intervals with imperfect information on abundance, yet these complexities are not incorporated into harvest models. Therefore, our objective was to assess performance of fall turkey harvest under a set of plausible management models that incorporated multi-year regulation cycles and observation uncertainty. We used stochastic simulation to assess performance of fall harvests for 5 management systems representing combinations of population assessment and regulation cycle frequencies. Because performance of harvests is sensitive to sex-specific harvest vulnerabilities, we simulated each management system under 3 levels of relative vulnerability (females less, equally, and more vulnerable than males), resulting in 15 simulation scenarios. For each scenario we conducted 1,000 replications of a 100 year population projection under each simulated harvest rate (0-15%). When hen vulnerability to harvest was high there were thresholds in performance metrics at fall harvest rates of 10–12%, where increases to harvest resulted in abrupt changes to performance. These thresholds resulted in decreased ability to maintain large populations through time and reduced annual harvest. Risk of population decline was negligible with annual decisions, but increased under multi-year cycles. We demonstrated that multi-year regulation cycles can be effective systems for sustaining turkey populations in the presence of observation uncertainty, but only when realized hen harvest is low. Existence of thresholds in responses of populations to fall harvest suggests multi-year management cycles are very risky when hen vulnerability is high. Thus, careful monitoring of hen harvest is important to ensure thresholds are not approached when implementing multi-year management cycles.