Sustainable Management Initiatives for the Southern African Hake Fisheries Over Recent Years
Abstract:The predominantly trawl fishery for hake contributes about half the landed value of all of South Africa's commercial fisheries, and is approaching the largest contributor to Namibia's gross domestic product (GDP). Two hake species are taken by these fisheries: shallow-water hake Merluccius capensis Castelnau, 1861 and deep-water hake Merluccius paradoxus Franca, 1960. The present management framework separates the resources into three areas: Namibia and the South African West and South Coasts. Some 30 yrs ago, particularly as a result of rapidly increasing foreign fishing effort over the preceding decade, all of these hake stocks had been severely depleted. We address the question of how successfully sustainable utilization and resource recovery has been achieved since that time. Although there has indeed been some recovery —to a greater extent for the stocks off South Africa—the historical record indicates over-optimistic appraisals of likely recovery rates and sustainable yield levels over this period, and some of the reasons for this are discussed. Certain key assessment questions remain: why is recruitment variability estimated to be so low, natural mortality so high, and why do estimates of stock-recruitment steepness, survey selectivity-at-age and bias in swept-area survey estimates differ so greatly between the stocks? For the most part, total allowable catch (TAC) for these fisheries over the past decade have been set using Operational Management Procedures (OMPs), pre-set rules applied to pre-specified resource monitoring data, where the selection of the procedure to be used is based upon simulation testing to ensure adequate robustness to uncertainties in data and model-structure, in the spirit of a precautionary approach. We discuss the ability in practice of this approach to achieve the necessary adaptive framework for management and summarize planned future initiatives towards refining this OMP approach. These include changing from the present species-aggregated to separate procedures for M. capensis and M. paradoxus. This is necessitated particularly by an increasing longline component in the South African hake fishery, which focuses on M. capensis and takes mainly 6+ aged fish, compared to the mainly 3+ by the trawlers.
Document Type: Research Article
Publication date: 2005-04-01
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