USFWS Migratory Bird Program James R. Kelley Mississippi Flyway Representative
Canvasback Harvest Strategy: Update for the 2008-09 Season
Strategy components • One continental population • Spring population objective ≥ 500,000 • Model of population dynamics……..
Canvasback population model: Number of canvasbacks next May = (Number this May × Summer survival + Number of Juveniles in Fall − Number killed in fall) × Winter survival
Fall Age Ratio Age ratio (immature/adult) Year O = Estimated from harvest data P = Predicted from pond model Preliminary estimate U.S. harvest data
Spring Abundance Canvasbacks (1000s) Year O = Estimated from survey data P = Predicted from canvasback model C,R,L,2 = 2009 model predictions for closed, restricted, liberal & 2-bird seasons
2008-09 Harvest Season Recommendation • Canvasback strategy calculates an allowable harvest of only 24,700 birds for the 2008-09 hunting season. • The predicted harvest under a restricted AHM season is 61,758 canvasbacks in the U.S. • The harvest strategy indicates a closed season for canvasbacks this year. • Under a closed season, the model predicts 537,519 canvasbacks in spring 2009.
2008 estimates of canvasback breeding population lowest since 2002; second lowest in last 15 years. • Canadian pond estimates are also low. • Preliminary harvest estimates for 2007 near model’s harvest prediction for a 2-bird bag. • 2007 model prediction failed by substantially overestimating 2008 breeding population. • Overestimate likely due in part to overestimation of the age ratio. • FWS is committed to model and harvest strategy improvements, as competing priorities allow.
Progress towards an assessment and decision making framework to inform scaup harvest management G. Scott Boomer U.S. Fish and Wildlife Service
Proposed Methodology to determine scaup regulatory alternatives Monitor BPOP & Harvest Update population parameters Harvest Derive policy Predict future state Harvest ~ f (Historical Regulations)
N = population size r = intrinsic rate of increase K = carrying capacity H = harvest e = process error
Assessing the Harvest Potential of Wood Ducks in Eastern North America