Construct a general bio-economic model applicable to each case study for which there exist appropriate data. Data requirements


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Construct a general bio-economic model applicable to each case study for which there exist appropriate data. Data requirements

  • Construct a general bio-economic model applicable to each case study for which there exist appropriate data. Data requirements

  • 1. Stocks

  • 2. Harvest

  • 3. Costs

  • 4. Revenue



The model should be

  • The model should be

  • 1. Dynamic

  • 2. Stochastic

  • 3. Capable of incorporating various management regimes

  • The model should be as simple as possible (one cohort) to facilitate computations.

  • Probably Matlab-based.



Sustainable utilisation of marine resources in the presence of volatile environment, both in the ecological, physical and economic sense.

  • Sustainable utilisation of marine resources in the presence of volatile environment, both in the ecological, physical and economic sense.

  • Based on a feedback model developed by Sandal and Steinshamn (1997a, 1997b, 2001a).



Feedback; optimal control (harvest) is a direct function of the state variable (stock)

  • Feedback; optimal control (harvest) is a direct function of the state variable (stock)

  • Deterministic and stochastic version

  • Non-linear input functions

  • Multi-species; cod and capelin, herring and cod

  • Aggregate model

  • Goal: Find the time path of harvest that maximises the present value of profits



Logistic growth functions

  • Logistic growth functions

  • Linear profit functions

  • Linear inverse demand function

  • Non-linear cost function

  • Interaction between species (cod and herring/capelin)



Revenue functions

  • Revenue functions

  • Cost functions







Introduced in 1995

  • Introduced in 1995

  • 25% of fishable stock (average of estimate at beginning of year and prediction for next year)

  • 155 thousand ton minimum

  • Change in 2000

  • minimum abolished

  • 30 thousand ton limit on TAC-changes from year to year

  • Change in 2006

  • Average of 25% of estimated stocks at the beginning of the year and last year catches

  • 30 thousand ton limit abolished



Change in 2006

  • Change in 2006

  • Average of 25% of estimated stocks at the beginning of the year and last year catches

  • 30 thousand ton limit abolished

  • Change in 2007

  • TAC set at 130 thousand tons for the fishing year 2007/2008

  • Average of 20% of estimated stocks, but a 130 thousand ton minimum





A harvest control rule can only be effective if




















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