SANCOR Newsletter Issue #172: March 2003
An ecosystem approach to fisheries management
in the southern Benguela
Lynne Shannon, of Marine and Coastal Management, arranged a workshop in Cape Town from 11-13 December 2002 to introduce the concept of an ecosystem approach to fisheries (EAF) management in the southern Benguela, and to examine the options for implementing an EAF in South Africa. Fifty scientists attended the meeting, including 15 scientists from outside of South Africa, who were able to share with us their diverse expertise in ecosystem modeling and management. A comprehensive suite of presentations on available modeling tools of potential use in ecosystem-based fisheries management was given by local scientists and by invited world leaders in the field, the latter also providing expert advice on the implementation of an EAF in South Africa. The aim of the workshop was to propose a framework of practical ways in which we could try to incorporate ecosystem considerations (including information from other types of multispecies approaches) into current Operational Management Procedures and other management strategies for South African marine resources. This will serve to guide our future ecosystem research and also to initiate the implementation of work underlying a major objective in our Act, namely that ecosystem considerations are directly included in our management, an aspect that is currently neglected in practice.
Modelling approaches which may have potential for an ecosystem approach to fisheries were considered. A focus at the workshop was on Ecopath with Ecosim, a biomass-based trophic ecosystem modeling approach, which has been extensively applied to the Benguela ecosystem. Model results, as well as strengths and weaknesses of the approach were discussed. Other modeling tools were also presented and discussed, including various multispecies approaches (such as Individual-Based ecosystem models, Minimum Realistic Models and specially developed hybridized ecosystem models applied in Australian fisheries). Additional tools available include the viability kernel approach, which has potential for simultaneously considering multiple management objectives, a Global Information System being developed for the southern Benguela, and the use of ecosystem indicators for fisheries management. Other aspects covered included how the needs of predators can be considered in fisheries management, and the management potential of Marine Protected Areas.
The last afternoon, workshop participants were divided into three groups for discussions on implementation of an EAF in South African fisheries, and its implications. It was recommended that an EAF be implemented as an incremental procedure with immediate effect, e.g. by starting to use ecosystem models to provide guidance on reference points and broader management objectives still currently set according to single-species assessments. This additional information would inform the advisory process, and would also feed back to the modelling process.
Suggestions on where and how to begin the process of incorporating ecosystem considerations into current management procedures included considering seabirds-pelagic fish relationships, exploring implications of hake interspecies cannibalism, and investigating the implications of catching species which are important prey for other commercial species, but also obvious candidates for an expanded fishery. It was suggested that an ecosystem modeling perspective be incorporated into existing single species management recommendations by testing these using ecosystem models. In this regard, it was strongly advised that robustness of ecosystem models to variability and uncertainty about input parameters be examined. Compilation of an ecosystem considerations document was recommended to initiate the process. A proposal was that a dedicated EAF working group be established at Marine and Coastal Management to coordinate the process of implementing an EAF in the various fisheries, and to provide over-arching guidance and ensure consistency in integrating existing data and information for informing the management process.
In summary, the main recurring points and themes of the workshop were:
1. We will have to adopt an EAF, policy pressure is on the increase.
2. We will need to involve all stakeholders in the EAF process and its development.
3. There are 2 kinds of models: a) strategic/testing models ("ecosystem", single species) and b) tactical/decision models ("single species"). Both types are complimentary.
4. The importance of considering spatial aspects in ecosystem models is recognized.
5. A suite of models will be required. Consideration needs to be given to the most suitable models to address the specified objectives.
6. An important requirement is validation through cross-validation or comparing output and data. Attention should be paid to robustness, although it was noted that full sensitivity is not always possible.
7. Ecosystem models provide a general framework; consistency should be ensured in the approaches taken for managing the different fisheries.
Lynne Shannon - Marine and Coastal Management
