Memorandum
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
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; (follow links to similar papers)
JEL-Codes: A10; (follow links to similar papers)
38 pages, July 1, 2008
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