Marine Resources

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Madalena Barbosa Marine Resources – April, 2012

Index
Common Property Fishery of N identical fishing vessels model: .................................................. 2 1.a) Biological Stock Equilibrium without Harvest .................................................................... 2 1.b) Maximum Sustainable Yield ............................................................................................... 2 1.c) Open Access Equilibrium .................................................................................................... 5 1.d) Optimal Economic Equilibrium .......................................................................................... 6 1.e) Comparison between Maximum Sustainable Equilibrium and both Open Access Equilibrium and Optimal Economic Equilibrium ....................................................................... 8 1.f) Assuming a schooling fishery .............................................................................................. 9 2. Different possible policies ....................................................................................................... 11 2.a) Total Allowable Catches ................................................................................................... 11 2.b) Effort and harvest taxes ................................................................................................... 13 2.c) Individual Transferable Quotas - ITQ’s ............................................................................. 15 3. Recommendation statement for the policy decision ITQ’s ..................................................... 16 Figure 1Growth and Harvest as function of stock size .................................................................. 8 Figure 2Sustainable revenue, total costs and net benefit of fishing effort. ................................. 8 Figure 3 Growth and Harvest as function of stock size for an Open Access equilibrium and a set TAC .............................................................................................................................................. 11 Figure 4 Sustainable revenue, total costs and Total revenue and total costs for the TAC level of fishing effort. ............................................................................................................................... 12 Figure 5 Use of corrective taxes on effort can equate social and private costs ......................... 14 Figure 6 Use of corrective taxes on harvest that can equate social and private revenues. ....... 15

Marine Resource Management – Assignment 2

1

Common Property Fishery of N identical fishing vessels model: Biological growth function for the resource stock: Ṡ= 1− ℎ = − ℎ

Graham-Schaefer production function (linear case of the Coob-Douglas production function):

Profit function:

Condition:

Where,

0≤

= ℎ − ≤

S(t): stock (biomass) of economically valuable fish at time t. E(t): Effort is an index measure of the quantity of inputs applied to the task of fishing at time t. Intrinsic growth rate of the resources stock: r = 0,8/Year Natural carrying Capacity (maximum value for S): k=50.000 tons Catchability coefficient: q = 0,0002/hour fishing Price per unit of output: p = 200€/ton Cost per unit of effort: c=400€/ hour fishing Maximum Effort per vessel: = 100 hours fishing

1.a) Biological Stock Equilibrium without Harvest
In this situation the growth in the stocks doesn’t exist so that: Ṡ=0 = = 50.000

1.b) Maximum Sustainable Yield
In order to calculate the values that maximize sustainable harvest for this fishery, we need to compute the harvesting function that depends on effort (Shaefer Yield Effort Curve); and after that, to maximize harvesting for effort so that we are able to compute the different sustainable values.

Marine Resource Management – Assignment 2

2

First we substitute the Graham-Shaefer production function into the biological growth...
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