A brief introduction to some approaches to multispecies/ecosystem modelling in the context of their possible application in the management of South African fisheries

Aspects of the potential application of multispecies/ecosystem modelling to advise the management of South African fisheries are discussed. In general, reliable predictive ability from such models is likely to be achieved sooner for top predators, because relatively fewer links need to be modelled. Accordingly, discussion concentrates on the deliberations of scientific workshops on modelling marine mammal – fisheries interactions held by two international marine mammal commissions during 2002. Five questions are posed, and some responses suggested, relating to the development of a framework for multispecies/ecosystem modelling to contribute to South African fisheries management: (1) should such models be used for testing or making decisions; (2) do they appreciably reduce uncertainties associated with single-species models; (3) are whole ecosystem or minimum realistic models more appropriate; (4) what computer software is best suited to implement such approaches; (5) what are the overall cost implications? Caution is expressed that general scientific acceptance of predictive reliability for such models (as required for their use for management) is unlikely in the short term, and will probably require considerable data collection and complex analysis at not insubstantial cost.

[1]  Villy Christensen,et al.  ECOPATH II − a software for balancing steady-state ecosystem models and calculating network characteristics , 1992 .

[2]  Bjarte Bogstad,et al.  A Multi-species Model for Fish and Marine Mammals in the Barents Sea , 1997 .

[3]  P. Yodzis,et al.  Local trophodynamics and the interaction of marine mammals and fisheries in the Benguela ecosystem , 1998 .

[4]  Villy Christensen,et al.  Ecospace: Prediction of Mesoscale Spatial Patterns in Trophic Relationships of Exploited Ecosystems, with Emphasis on the Impacts of Marine Protected Areas , 1999, Ecosystems.

[5]  Susan J Johnston,et al.  Development and application of management procedures for fisheries in southern Africa , 1999 .

[6]  André E. Punt,et al.  Experiences in the evaluation and implementation of management procedures , 1999 .

[7]  J. Cooke,et al.  Improvement of fishery-management advice through simulation testing of harvest algorithms , 1999 .

[8]  Villy Christensen,et al.  Representing Density Dependent Consequences of Life History Strategies in Aquatic Ecosystems: EcoSim II , 2000, Ecosystems.

[9]  Astrid Jarre,et al.  Modelling effects of fishing in the Southern Benguela ecosystem , 2000 .

[10]  Carl J. Walters,et al.  Ecopath, Ecosim, and Ecospace as tools for evaluating ecosystem impact of fisheries , 2000 .

[11]  Keith Sainsbury,et al.  Symposium overview: incorporating ecosystem objectives within fisheries management , 2000 .

[12]  A. Hollowed,et al.  Marine fisheries stock assessment improvement plan : report of the National Marine Fisheries Service, National Task Force for improving fish stock assessments , 2001 .

[13]  Morten Vinther.  Ad hoc multispecies VPA tuning applied for the Baltic and North Sea fish stocks , 2001 .

[14]  Astrid Jarre,et al.  Trophic flows in the southern Benguela during the 1980s and 1990s , 2003 .

[15]  T. Tamura,et al.  Regional assessments of prey consumption and competition by marine cetaceans in the world. , 2003 .

[16]  André E. Punt,et al.  The role of harvest control laws, risk and uncertainty and the precautionary approach in ecosystem-based management. , 2003 .

[17]  E. Fulton,et al.  Effect of complexity on marine ecosystem models , 2003 .

[18]  Carl J. Walters,et al.  Modelling stock dynamics in the southern Benguela ecosystem for the period 1978–2002 , 2004 .

[19]  J. Polovina,et al.  Model of a coral reef ecosystem , 1984, Coral Reefs.

[20]  Doug S Butterworth,et al.  A critical look at the potential of Ecopath with ecosim to assist in practical fisheries management , 2004 .

[21]  K. Magnússon,et al.  An overview of the multispecies VPA — theory and applications , 1995, Reviews in Fish Biology and Fisheries.

[22]  Carl J. Walters,et al.  Ecopath with Ecosim: methods, capabilities and limitations , 2004 .

[23]  C. Walters,et al.  Structuring dynamic models of exploited ecosystems from trophic mass-balance assessments , 1997, Reviews in Fish Biology and Fisheries.

[24]  L. Shannon,et al.  An ecosystem framework for fisheries management in the southern Benguela upwelling system , 2004 .

[25]  D. Butterworth,et al.  Consideration of multispecies interactions in the Antarctic: a preliminary model of the minke whale – blue whale – krill interaction , 2004 .

[26]  K. Cochrane,et al.  Ecosystem approach to fisheries management in the southern Benguela: a workshop overview , 2004 .