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Models used for resource management are rooted in ecological theories on the functioning of populations and ecosystems, which have undergone paradigmatic changes over the past decades. The concept of equilibrium states of populations and ecosystems has been confronted with that of ever changing states of biotic entities, and the role of environmental vs. biological forcing („bottom-up, top-down“) in determining population sizes and harvest potentials of aquatic resources is hotly debated. Depending on the type of resource (long-lived, short-lived; tropical, temperate; fish, invertebrate etc.), data availability, level and kind of training of fisheries modeller, a diverse set of models are presently being applied for the management of aquatic resources. The ZMT working group resource management concentrates on the following main themes:
Single species stock assessment
Traditional tools and models for single species stock assessment are being applied to coastal resources of the tropics to derive estimates of current exploitation rates and to provide the basis for a sustainable fishery. In doing so, vital population parameters such as growth and mortality rates are being determined and factors are identified that determine the stock-recruitment relationships and interannual fluctuations in stock sizes.
Ecosystem based resource modelling
In recent years the ecosystem-based modelling approach (EBMA) has gained much ground worldwide, as it allows to model the resource in its ecosystem context and to explore the effect of resource use and/or protection via marine protected areas (MPAs) on the socio-ecosystem. At the same time, an increasing number of scientists have tried to also incorporate climate variability into the fisheries models allowing for improved harvest predictions.
The Resource Management group at the ZMT follows the EBMA approach and also looks into the role of climate variability in regulating resource productivities. Through computer simulations of resource use and climate impact scenarios, resource management recommendations are being elaborated, which also take into account the socio-economic context of the fishery.