Strategy components 1)One continental population 2)Spring population objective ≥ 500,000 3)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 Year Age ratio (immature/adult) O = Estimated from harvest data P = Predicted from pond model Preliminary estimate U.S. harvest data
Spring Abundance Year Canvasbacks (1000s) 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 1)Canvasback strategy calculates an allowable harvest of only 24,700 birds for the 2008-09 hunting season. 2)The predicted harvest under a restricted AHM season is 61,758 canvasbacks in the U.S. 3)The harvest strategy indicates a closed season for canvasbacks this year. 4)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.2008 estimates of canvasback breeding population lowest since 2002; second lowest in last 15 years. Canadian pond estimates are also low.Canadian pond estimates are also low. Preliminary harvest estimates for 2007 near model’s harvest prediction for a 2-bird bag.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.2007 model prediction failed by substantially overestimating 2008 breeding population. Overestimate likely due in part to overestimation of the age ratio.Overestimate likely due in part to overestimation of the age ratio. FWS is committed to model and harvest strategy improvements, as competing priorities allow.FWS is committed to model and harvest strategy improvements, as competing priorities allow.