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Fisheries management must look at what slips through the net

Gepubliceerd op
3 oktober 2013

Managing fish stocks, for instance by using quota, often results in the opposite of what is intended. Scientists of Wageningen UR have developed a model that accounts for the complexity of the system: management councils, fishermen and other stakeholders. The model shows there are tipping points; a small error in management can lead to a system breakdown. One of the researchers, Guus ten Broeke of Biometris, obtained a prize for a poster presentation on this topic.

A pressing concern in the tuna fisheries of the Western and Central Pacific Ocean is the current overcapacity. This threatens both economic and ecological sustainability and produces significant economic waste. Various management schemes for increased sustainability have been implemented; thus far the result has been a mixture of success and failure. The question is: why?

An important reason is that fisheries are complex adaptive systems. Management policies consider fisheries as fully controllable and predictable, but fishermen are influenced by many other ecological, economic, social and political factors. They have their own agenda and act accordingly, which may lead to surprising outcomes.

Stella Libre of the Environmental Policy group and Guus ten Broeke of Biometris, together with other scientists of Wageningen UR, have identified relevant factors influencing fisherman behaviour, by interviewing fishers and other stakeholders. They incorporated these factors in a mathematical model, which aims at exploration of the effects of different kinds of policy measures on ecological and economic sustainability.

Preliminary results show that in some cases the outcome may depend quite critically on the managing policy. A slight increase of the pressure in a certain direction may radically turn the whole process around, and might even lead to a full collapse of the fishery system. Such a feature is called a tipping point. Awareness of this behaviour will lead to more effective and safe ways to reach a sustainable catch level. At a recent conference of the European Social Simulation Association in Warsaw, Guus was awarded a prize for the best student poster, based on this work.