FishSlides

FishSlides - Fisheries Introduction Economic and policy...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
11/3/2011 1 Fisheries Introduction: Economic and policy issues Population dynamics Sustainable catch-effort diagram Bio-economic equilibria Free access. Sole owner Traditional fishery management Limited entry Season closures Gear restrictions
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/3/2011 2 Fisheries (cont.) Rights-based management •I T Q s Private harvester agreement, cooperatives •T U R F s Protecting marine ecosystems Protecting marine habitats Controlling bycatch Aquaculture: Promise and problems
Background image of page 2
11/3/2011 3 Fisheries (cont.) Rights-based management •I T Q s Private harvester agreement, cooperatives •T U R F s Protecting marine ecosystems Protecting marine habitats Controlling bycatch Aquaculture: Promise and problems
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/3/2011 4 Components of stock dynamics Recruitment during year t Growth of individuals during year t Catch during year t Mortality during year t Change in stock during year t
Background image of page 4
11/3/2011 5 Logistic model of population dynamics Assumes recruitment, growth, and mortality are determined by S(t) . Natural growth is f(S(t)) . With catch, Q, equation for popul’n dynamics is ) ( )) ( ( ) ( t Q t S f dt t dS Specific logistic growth function: ) ( )) ( )( ( ) ( t Q t S K t aS dt t dS K is carrying capacity; ‘ ’ is adjustment speed.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/3/2011 6 Numerical example of logistic model ) ( )) ( 100 )( ( 01 . ) ( t Q t S t S dt t dS
Background image of page 6
11/3/2011 7 Natural growth Stock S(t), tons tons per year K Logistic growth model
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/3/2011 8 Sustainable catch, Q Stock S, tons tons per year K Sustainable yields Note: dS(t)/dt = f(S(t)) - Q(t), so if Q(t) = f(S(t)), the stock is constant. MSY
Background image of page 8
11/3/2011 9 Sustainable catch, Q tons per year Sustainable catch-effort curve Effort E Stock S E C MSY Note: With some growth functions and harvest technologies there may be a critical effort level, E C , beyond which positive yields cannot be sustained.
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/3/2011 10 Deriving Catch-Effort Relationship for Logistic Model 1. Population Growth, net of catch : ) ( )) ( ( ) ( t Q t S f dt t dS Example: ) ( )) ( 100 )( ( 01 . ) ( t Q t S t S dt t dS . Questions: In the absence of any catch, what is the equilibrium level of the stock? What level of stock maximizes the sustainable yield? 2. Production Function for Catch: )) ( ), ( ( ) ( t E t S G t Q Example: ) ( ) ( 1 . ) ( t E t S t Q Problem: Express S (unobservable) in terms of Q and E (both observable).
Background image of page 10
11/3/2011 11 3. Solve for Steady State Catch as Function of Effort (i) In a steady state equilibrium, 0 ) ( dt t dS . Therefore, ) ( )) ( ( t Q t S f and all variables are constant over time so we drop t arguments in functions. Example: Q S S ) 100 ( 01 . . (ii) We need to replace S , which is unobserved, by a function of E and Q , which are observed. To accomplish this, use the production function ) , ( ) ( E S G t Q and solve for S . Example: Production function SE Q 1 . implies E Q S 10 .
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/3/2011 12 3. Solve for Steady State Catch as Function of Effort (cont.) (iii) Finally, substitute the expression for S from step (ii) into the relationship between steady state Q and S from step (i). Solve the resulting equation for steady-state catch, Q , as a function of effort, E .
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/26/2011 for the course ECON 122 taught by Professor Staff during the Fall '08 term at UCSB.

Page1 / 65

FishSlides - Fisheries Introduction Economic and policy...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online