Transcript Slide 1

Harvest Management in an
Integrated Framework
Michael C. Runge
USGS Patuxent Wildlife Research Center
Outline
Harvest Management
 Integrating Harvest & Habitat Management
 Multiple Objectives

Harvest Management
Oh no, Not Yield Curves Again!
Recruitment or Mortality
Carrying Capacity & Harvest
Additional mortality
due to hunting
Natural mortality
Neq
K
Continental Population Size
Sustainable Harvest
12
1.4
“K”
1.2
10
8
Neq*
6
4
Annual Harvest
Equilibrium N
1
0.8
0.6
0.4
2
0
0.2
0
0.05
0.1
0.15
Harvest rate
0.2
0
0
0.05
0.1
0.15
Harvest rate
0.2
5
Yield Curve
h = rmax/2
Sustainable Annual Harvest
rmaxK/4
h = rmax
0
0
h=0
N* = K/2
Equilibrium Population Size (N)
K
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
Annual Harvest (thousands)
1000
Pre-1975
(53.6)
800
L3
L2
600
L1
400
R1, SIS
R1
Post-1975
(55.6)
200
0
0
2
4
6
8
10
Latitude-adjusted BPOP (millions)
12
Yield Curves for Habitat Management
2.0
Sustained Annual Harvest
1.8
Increase
productivity on
existing parcels
1.6
Increase
capacity on the
landscape
1.4
1.2
1.0
0.8
0.6
Current
0.4
0.2
0.0
0
2
4
6
8
Equilibrium BPOP
10
12
14
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
 H u  Nˆ  where u  N   min 1, N 8.8M 

t 0

t
t 1
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
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.
2.
3.
4.
5.
6.
7.
8.
9.
10.
maximize harvest
keep harvest sustainable for all species
avoid closed or partial seasons
maximize the frequency of long seasons
have relatively stable regulations
have relatively simple regulations
keep populations near the NAWMP goals
motivate hunter participation
motivate habitat conservation
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 tradeoffs in setting harvest regulations?
 Do we currently have a framework for this
sort of deliberation?

Sustainable Annual Harvest
Coherent Objectives
NA goal
Desired
Harvest
Policy
Desired
Habitat
Current
Condition
Worse
Equilibrium BPOP
19
Summary
Summary

Harvest Management


Integrating Harvest & Habitat Management



Yield curves are a valuable tool
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