Assessment of management options in marine fisheries by qualitative modelling techniques

An effective management of the rapidly dwindling marine fish resources is o f great ecological, economic and social importance for the future. An over- development of commercial fisheries has brought about a multitude of negati ve environmental impacts, such as an accelerated exploitation of stocks or a decrease of marine biodiversity, and furthermore, a profound structural c hange in fish industry. However, the main reason for the non-prosperous rat ioning of marine resources is the lack of knowledge about certain processes as well as the non-availability of adequate steering instruments. This pap er addresses the lack of conceptualization in the case of uncertain knowled ge. tt proposes a model approach which can be used for weak but improved de cision support under the premise of vague knowledge. The usage of qualitati ve differential equations illustrates general patterns of overcapitalizatio n of fishing fleets. The extension of traditional model approaches by integ ration of additional socio-economic phenomena in this context supplies deep er insights in the dynamics of a coupled economic and ecological system. Th e approach provides a set of characteristic system behaviours which can be fruitfully used for the development of future management tasks. (C) 2001 El sevier Science Ltd. All rights reserved.