FISHERIES_2017_JUL_SWG-DEM_20 Kingklip assessment.pdf (909.41 kB)

Updated assessment of the South African kingklip resource that includes catch-at-length data for the one-stock and two stock hypotheses

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posted on 20.07.2021, 13:05 by Anabela Brandao
This paper updates the kingklip assessments by Brandão and Butterworth (2008a and 2008b) which incorporated catch at length data in the assessment models by taking further and updated data into account. Further, the analysis of the two stock hypothesis model is extended to the West coast as well. If the resource is treated as two separate stocks, current (2017 for West coast and 2016 for the South coast) depletion of spawning biomass on the West and South coasts is estimated at 0.64 and 0.85 respectively. A similar status is obtained with the resource treated as a single stock, which yields a current depletion estimate of 0.72. A more pessimistic picture is obtained with the West coast selectivity functions assumed for both one and two stock hypotheses models, especially for the two stock hypothesis for the South coast, which yields a current depletion estimate of 0.43. However the fit to the catch at length data from both the surveys and the commercial fishery is worse in this case. The two sensitivity tests investigated for the one stock hypothesis show similar results to those obtained for the base case model.

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Department of Mathematics and Applied Mathematics, University of Cape Town