Lecture 6 Harvest Under the D-D model

Question 1

Estimating # from a harvested Population

Answer 1

-Estimate total harvest (Ĥ)

→By hunter surveys, restrations, check stations, etc

-Estimate harest rate (ĥ)

→By band returns, reward tags, etc

-Estimate pre-hunt populations using canonical formule

N_pre-hunt=H/h

Question 2

Harvesting and the Logisstic Model

Answer 2

-Goal: produicing a sustainable “offtake”

→Often we want this offtake maximized over some period, ie, Maximum Sustained Yield (MSY)

-Two main approached

→Quota (fixed)

→Effort (fixed)

-Improvements prevent harvest until a minimum “threshold” is met

→Constant Escapement (w/Quota systems)

→Fixed Effort w/ threshold

Question 3

What do we need to know to make D-D Harvest work well?

Answer 3

-Good Data

→N,K,h and H need to be monitored and measured precisely

→This is ofthen very difficult

-Good biological understanding of out species

→Form of densitydependence (θ)

→How harvest influence population response

-Keep assumptions of the underlying modle in mind

Question 4

Biological Considerations for the D-D model for harvest

Answer 4

• Hunters are predators

→There are notavle difference to consider

-DD harvest Managment

→Assumes that DD responses are altered

⇒Mortality: compensatory/Additive

-Rule of thumb

→Fast life histories can sustain higher hunign rates

Question 5

-How does harves influence population cital rates

→Mortality: compensatory/Additive

Answer 5

Look at PowerPoint slide 5

Question 6

Fixed quota harvest strategy

Answer 6

Look at PowerPoint Slide 1

Question 7

Fixed Effort Harvesting

Answer 7

Look at PowerPoint Slide 2

Question 8

Fixed-effort harcesting w/theshold

Answer 8

Look at PowerPoint Slide 3

Question 10

Who do we harvest?

Answer 10

• Many harvest, esp. large game are male-focused
• This is justifiable, but think about the assumptions of the D-D model
• Other condideration of taking males

→Low effective population size

→Alteration of social interactions

→Genetic Changes

Question 11

Key points fot D-D harvest

Answer 11

• Logistic growht modles are commonlu used to guide harvest managment
• Sustainable harvest under theses models:

→Good date ( K, form of density dependence, encironmental effects)

→Ability to modify harvest effort or efficiency based on the about data