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Assessment of teal harvest potential Progress and preliminary results 1. Description of the population dynamics of each species 2. Derivation and distribution.

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Presentation on theme: "Assessment of teal harvest potential Progress and preliminary results 1. Description of the population dynamics of each species 2. Derivation and distribution."— Presentation transcript:

1 Assessment of teal harvest potential Progress and preliminary results 1. Description of the population dynamics of each species 2. Derivation and distribution of the harvest 3. Assessment of past and current harvest pressure 4. Assessment of population response to harvest pressure 5. Assessment of the impacts of incremental regulatory changes on harvest, particularly with regard to special seasons Tasks assigned by the SRC:

2 1. Description of the population dynamics of each species -- Survival and recovery rates Analysis for all (3) species Sex, age, and group effects; harvest season effects --Production indices Blue- and green-winged teal only Age ratios with fixed or annual DV, estimates and standard errors from Bayesian estimation Female AR with fixed DV --Population model balance equation, following MCM model: BPOP t+1 = BPOP t {mS t,AM + (1 – m)[S t,AF + AR t (S t,JF + (S t,JM *S msum /S fsum ))]}

3 2. Derivation and distribution of the harvest --BWTE: Szymanski and Dubovsky (in press) --AGWT: Dubovsky MRPP analysis Blue-winged teal Green-winged teal

4 --Recovery rates from 1965 to 2009 for each age and sex cohort were converted to harvest rates using annual composite reporting rates estimated for region, band type, and reporting method --Blue-winged teal: two sets of composite reporting rates were calculated to represent high and low bounds on reporting rates south of the US border: 3. Assessment of past and current harvest pressure Year Reporting rate

5 S 0 a = S 0 c = S 0 a = S 0 c = Kill rate Survival rate Kill rate Survival rate 4.Assessment of population response to harvest pressure BWTE -- Additive vs. compensatory harvest

6 1.Developed survival and recruitment models for balance equation 2.9 predictions of optimal harvest, optimal harvest rate, and K for each species: Compensatory, low pond count Compensatory, average pond count Compensatory, high pond count Additive, low pond count, low reporting rate Additive, low pond count, high reporting rate Additive, average pond count, low reporting rate Additive, average pond count, high reporting rate Additive, high pond count, low reporting rate Additive, high pond count, high reporting rate 3. Reporting rate only affects equilibrium harvest dynamics for additive model 4. Additive model predictions of optimal harvest rate higher if reporting rate is low 5. Optimal harvest under compensatory model is higher than additive model 4.Assessment of population response to harvest pressure --Optimal equilibrium dynamics

7 5.Assessment of the impacts of incremental regulatory changes on harvest, particularly with regard to special seasons How do populations respond to changes in early harvest seasons? --Analyzed relationship between early harvest/harvest rate and early season structure calculated early season harvest rates from US direct recovery rates using composite reporting rate --Compared regression models of early season harvest/harvest rate on early season states, early season days, harvest age ratio, and BPOP by flyway --Some significant relationships between early season states and early season days and either BWTE or AGWT, but no consistent patterns among flyways or between harvest rate and harvest. --Lack of variation in early season structure limits the degree to which inferences could be made about the effects of changing # days or # states --Ultimately the harvest is determined by hunter pressure, which is only partially controllable by season structure.

8 Teal Assessment Findings: --Summary of available information on population dynamics of 3 species --Estimates of sustainable harvest and harvest rates for blue- and green- winged teal under a range of scenarios and assumptions --Some information on how harvest is influenced by changing season structure --Assessment limited by information available (e.g., cinnamon teal) --No recommendations for harvest strategies

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