Ecosystem-based fisheries management of cod and sprat in the Baltic Sea

Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, The Netherlands

Floor Soudijn

Floor Soudijn

The majority of commercially exploited fish stocks suffer from overfishing. This has led to the collapse of several fish populations. To improve fisheries management, fish stocks must be considered as interrelated elements of the ecosystem they inhabit. The fishing industry preferentially targets large predatory fish, such as cod, as these are often most profitable. These predatory fish critically depend on prey fish, such as sprat, for their survival and growth. Typically, these prey fish are also subject to commercial fishing. Even though it has become widely recognized that fisheries management should account for trophic interactions and multiple impacts in fishery systems, it is proving difficult to operationalize this approach.

Classic fisheries models are missing some essential biological mechanisms and therefore lack the power to handle this kind of complexity. This hinders the reliability of predictions of the effects of fishing and the establishment of optimal exploitation targets in systems of interrelated stocks. First, in most fisheries models, growth and reproduction are considered independent of the available amount of prey fish and other resources: yet, to account for feedbacks between a predator and its prey, growth and reproduction need to be analyzed as the food-dependent processes that they are. Second, seasonal rhythms, especially in the reproductive outputs of fish stocks, need to be taken into account, as seasonal variation in prey availability strongly affects the predator, feeding back on the prey. The aim of this project is to develop and examine these two extensions in an improved fisheries model, to elucidate how the fishing of cod and sprat affects the Baltic Sea ecosystem.

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Last edited: 24 March 2016

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