Evaluating the implementation efficacy of an ecosystem approach to fisheries in the South African anchovy fishery
A knowledge-based tool was developed to assess the efficacy of the ecosystem approach to fisheries in the South African anchovy fishery. South Africa has agreed to implement an ecosystem approach to fisheries (EAF) management. The EAF management comprises of three dimensions; ecological well-being, human well-being and ability to achieve. The focus for this study was on the ecological well-being dimension. Meetings were held with experts to revise objectives stemming from issues in the anchovy fishery documented earlier and indicators linking to these objectives. A hierarchical tree was constructed using these indicators and objectives. The objectives were divided into pressure and state. The indicators were transformed using piecewise linear transformation on to a common scale from -1 to 1. Thresholds were also decided to assess when the EAF implementation was considered to be 'good' (1), 'ok' (0) and 'bad' (-1). Weighted means were applied through the hierarchy. The overall resulting output, the truth value, was then used to assess how well the ecological dimension of the anchovy fishery had been doing over time. This showed the implementation efficacy of an EAF within the ecological dimension had been doing badly in 1987-1996, and since 1997 the ecological dimension of the EAF has been doing better. Sensitivity tests on the weights also showed that the knowledge based tool was robust to changes in weights. This allowed for experts to have slight differences in opinion over the way the weights should be distributed, but without these differences in opinion affecting the overall truth value. Sensitivity tests on the thresholds of one of the indicators showed that the outcome of the indicator is sensitive to changes in the thresholds. However, when looking at the overall truth values or the objectives, the changes to the thresholds did not affect the resulting objective values or the overall truth value that much. Although the indicator values change with changes in the thresholds, looking at the whole knowledge based tool it is fairly robust to moderate changes in thresholds.
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