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Harvest Management in an Integrated Framework
Michael C. RungeUSGS Patuxent Wildlife Research Center
Outline Harvest Management Integrating Harvest & Habitat Management Multiple Objectives
Harvest Management
Oh no, Not Yield Curves Again!
Carrying Capacity & Harvest
Neq
Re
cru
itm
en
t o
r M
ort
alit
y
Continental Population Size
K
Additional mortality due to hunting
Natural mortality
Recruitment
0 0.05 0.1 0.15 0.20
2
4
6
8
10
12
Harvest rate
Equ
ilibr
ium
N
0 0.05 0.1 0.15 0.20
0.2
0.4
0.6
0.8
1
1.2
1.4
Harvest rate
Ann
ual H
arve
st
“K”
Neq*
5
Sustainable Harvest
Sus
tain
able
Ann
ual H
arve
st
Equilibrium Population Size (N)0 N* = K/2 K
0
rmaxK/4
h = rmax
h = rmax/2
h = 0
Yield Curve
Harvest Management At least implicitly, since 1995, the
dynamics captured by yield curves have been at the heart of our harvest assessments
The focus on K makes it clear that harvest dynamics really cannot be understood without the context of habitat management
Integrating Harvest & Habitat Management
Coherent Models If we had a common modeling framework for
harvest and habitat management: We could understand how habitat management is affecting
continental demographics, including harvest potential We could understand how harvest management affects the
continental population size, and hence, the use of available habitat
Continental carrying capacity (K) is a useful metric that links harvest and habitat management Yield curves are, in fact, an extremely valuable way to look
at habitat management
Pintail Harvest Potential
0 2 4 6 8 10 12
Latitude-adjusted BPOP (millions)
An
nua
l Ha
rves
t (th
ous
and
s)
0
200
400
600
800
1000
R1
L1
L2
L3
R1, SIS
Pre-1975(53.6)
Post-1975(55.6)
0 2 4 6 8 10 12 140.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Equilibrium BPOP
Sus
tain
ed A
nnua
l Har
vest
Current
Increase productivity on existing parcels
Increase capacity on the
landscape
Yield Curves for Habitat Management
Integrated Modeling Benefits
Track changes in habitat (positive or negative) and account for their effects on harvest potential
Evaluate effects of habitat management on continental demography
Understand how waterfowl objectives are affected jointly by harvest and habitat management
Challenges Understanding how JV actions affect continental K Do we have the institutional structure in place to build
integrated models?
Multiple Objectives
Current AHM Objective Function
This is a composite of several objectives, with an implicit method of weighting: Maximize annual harvest of MCM Maintain sustainable harvest of MCM Discourage population size < NAWMP goal Don’t allow closure above 5.5M MCM
10
ˆ where min 1, 8.8t tt
NH u N u N M
Multiple Harvest Objectives But the current AHM objective function
leaves out many other possible objectives Sustainable harvest of other species Avoid partial seasons or closure for other spp. Encourage hunter participation Provide widespread hunting opportunity Motivate habitat conservation Maintain historical distributions during winter And many others…
Turning Point question
What are your top TWO objectives for waterfowl harvest management?
1. maximize harvest 2. keep harvest sustainable for all species 3. avoid closed or partial seasons 4. maximize the frequency of long seasons 5. have relatively stable regulations 6. have relatively simple regulations 7. keep populations near the NAWMP goals8. motivate hunter participation 9. motivate habitat conservation10. other
Multiple Waterfowl Objectives And the larger endeavor adds even more
objectives: Achieve NAWMP population objectives
What fundamental goals drive these? Minimize costs of habitat conservation Engage partners Maintain and motivate a traditional hunting
culture Generate broad public support for wetland habitat
conservation Etc.
Trade-offs Harvest management is embedded in a
broader context with a complex set of objectives
There are trade-offs among these objectives They cannot all be achieved perfectly
How do we evaluate and balance the trade-offs in setting harvest regulations?
Do we currently have a framework for this sort of deliberation?
Equilibrium BPOP
Su
sta
ina
ble
An
nua
l Har
vest Desired
Habitat
NA goal
19
Desired Harvest Policy
Coherent Objectives
Current Condition
Worse
Summary
Summary Harvest Management
Yield curves are a valuable tool Integrating Harvest & Habitat Management
Continental K is a valuable common metric Coherent models would allow us to understand how
harvest potential is changing due to NAWMP activities and other factors
Multiple Objectives Harvest management, let alone integrated management, is
a complex multiple-objective problem We need a framework to understand and balance the
trade-offs among objectives Coherent monitoring could arise out of such an integrated
framework