Scandinavian Working Papers in Economics

Memorandum,
Oslo University, Department of Economics

No 16/2008: Optimal Age- and Gear-specific Harvesting Policies for North-East Arctic Cod

Florian K. Diekert (), Dag Ø. Hjermann, Eric Nævdal and Nils Chr. Stenseth
Additional contact information
Florian K. Diekert: Centre for Ecological and Evolutionary Synthesis, Postal: Department of Biology, University of Oslo, P.O Box 1066 Blindern, N-0316 Oslo, Norway
Dag Ø. Hjermann: Centre for Ecological and Evolutionary Synthesis, Postal: Department of Biology, University of Oslo, P.O Box 1066 Blindern, N-0316 Oslo, Norway
Eric Nævdal: Dept. of Economics, University of Oslo, Postal: Department of Economics, University of Oslo, P.O Box 1095 Blindern, N-0317 Oslo, Norway
Nils Chr. Stenseth: Centre for Ecological and Evolutionary Synthesis, Postal: Department of Biology, University of Oslo, P.O Box 1066 Blindern, N-0316 Oslo, Norway

Abstract: We examine optimal harvest policies in a multi-cohort, multi-gear bioeconomic model of North-East Arctic cod (Gadus morhua) which includes cannibalism and contains broader ecosystem effects. By controlling the selectivity of the different Fishing equipment, we can partially target different age cohorts. We show that cur- rent gear selectivity implies that the wrong Fish are targeted. Optimization shifts the exploitation pattern towards older and heavier Fish. This increases the harvested biomass while reducing the number of Fish removed from the ocean. The result is a much more robust and abundant cod stock with an age/size distribution closer to the stocks natural state. We optimize the Net Present Value (NPV) generated by the Fishery by letting effort and selectivity be the control variables and and that NPV may be more than doubled, even when only gear selectivity or harvest effort is allowed to vary.

Keywords: Bioeconomics; North-East Arctic cod: Age-structure; Gear selectivity; Optimal harvest policies

JEL-codes: A10

38 pages, July 1, 2008

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