Assessment and management of Cape horse mackerel Trachurus capensis off Namibia based on a fleet-disaggregated age-structured production model

  • C Kirchner
  • G Bauleth-D’Almeida
  • MR Wilhelm

Abstract

The Cape horse mackerel stock off Namibia is assessed using a fleet-disaggregated age-structured production model including historical International Commission for the Southeast Atlantic Fisheries (ICSEAF) and current data. Data from acoustic biomass surveys, on commercial catch per unit effort and on commercial catch-at-age, were used to estimate current stock status over a range of model specifications. A management tool, the so-called management monitor graph, was introduced in order to track past management relative to stock status. Target, limit and precautionary reference points, decision rules and harvesting strategies, according to which the stock should be managed, are described and tested. The target reference point was set at maximum sustainable yield (MSY), the precautionary reference point at 80% of MSY and the limit reference point at 30% of MSY. Owing to some inconsistencies in the dataseries, evaluation of the current state of the resource is challenging, but estimates are that the resource is around the MSY level, somewhere between 250 000 and 300 000 t.

Keywords: assessment, management, Namibia, Trachurus capensis

African Journal of Marine Science 2010, 32(3): 525–541

Author Biographies

C Kirchner
Ministry of Fisheries and Marine Resources, PO Box 912, Swakopmund, Namibia
G Bauleth-D’Almeida
Ministry of Fisheries and Marine Resources, PO Box 912, Swakopmund, Namibia
MR Wilhelm
Ministry of Fisheries and Marine Resources, PO Box 912, Swakopmund, Namibia;  Current address: Marine Biology Research Centre, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X