Harvest Management in an Integrated Framework

Michael C. RungeUSGS Patuxent Wildlife Research Center

Outline Harvest Management Integrating Harvest & Habitat Management Multiple Objectives

Harvest ManagementOh no, Not Yield Curves Again!

Carrying Capacity & Harvest

Neq

Rec

ruitm

ent o

r Mor

talit

y

Continental Population SizeK

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)

Ann

ual H

arve

st (t

hous

ands

)

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

Sus

tain

able

Ann

ual H

arve

st 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