Critical Interactions BEtween Species and their Implications for a PreCAUtionary FiSheries Management in a variable Environment - a Modelling Approach

Funding Period: 2004-2007

Funding: European Union, 6th framework TP 8.1, Contract no.: 502482

Website: Uni-Hamburg/BECAUSE

Contacts: Dr. Jens Floeter, Alexander Kempf

Description

BECAUSE investigates the quantitative role of species interactions as a first step towards the implementation of the ecosystem approach into fisheries management. The focus is on simple but critical interactions in the upper trophic levels of marine food webs. This refers specifically to the interactions between exploited prey fish populations, exploited fish predators and wild life such as sea birds and marine mammals dependent on the same prey fish populations. In most European shelf ecosystems fish predator populations are severely depleted, and this has released predation pressure on prey fish populations substantially. In part, man has taken over the role and harvests this part of the prey fish production either for human consumption or for reduction to fish meal. An exact quantitative understanding of these interactions becomes essential, once recovery plans for the over fished predator stocks become operational and effective. The interactions targeted for investigation are sandeel/predator fish, nephrops/cod, capelin/cod herring/cod, sprat/cod, hake/prey fish, hake and cod cannibalism. These interactions will be studied in 5 different case studies: Nordic Seas, North Sea, Baltic Sea, Iberian Shelf/Bay of Biscay and Mediterranean Sea. The analysis will start with the development of conceptual food web models in each case study. This will include the detailed analysis of processes driving critical interactions, mainly prey selection, predator prey overlap and its dependence on biological and hydrographical factors, consumption, growth and maturity. Special emphasis will be given on updates of the population numbers of dependent wild life and revisions of their feeding behaviour and food requirements. The process analysis results in improved process models which are in turn used to improve existing multi species models. These models will be further developed and investigated with regard to inherent structural and stochastic uncertainty. Hind-cast runs will be performed to explore the trophic relationships in contrasting system states. Optimised multi-species models will finally be used to produce forecast predictions for different management scenarios taking into account environmental regimes and the food requirements of seabirds and marine mammals. Precautionary reference points and limit values will be identified as criteria to be used in management measures to prevent risk situations.