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Integrating marine mammal populations and rates of prey consumption in models and forecasts of climate change-ecosystem change in the North Atlantic Ocean.

Santos M B1,2 and Pierce G J1,2

1Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, Apdo. 1552, 36200 Vigo, Spain

2University of Aberdeen, School of Biological Sciences, Tillydrone Avenue, Aberdeen AB24 2TZ, Scotland, UK

The ICES Science Plan identifies research on climate change processes and predictions of its impacts as a High Priority Research topic for 2009-2013. Marine mammals, as top predators of the marine food web, play an important role in controlling prey populations and changes in their distribution and abundance are expected as a result of climate/global change.

Results from large-scale international surveys in the Northeast Atlantic have shown that most cetacean populations have not experienced large changes in abundance during the last 10 years but harbour porpoise (Phocoena phocoena) distribution has shifted towards southern waters. Changes in distribution have also been inferred from strandings and sightings data. Grey and harbour seal numbers have shown contrasting trends over the years. Changes in diet have been recorded in several species for which long-term data are available.

There is a wealth of data available for use in ecosystem models (e.g. trophodynamic models, multispecies VPA, etc.). Existing models have highlighted the need to take into account the complexities inherent in predator-prey relationships (e.g. how predators respond to changing availability of different prey, i.e. multispecies functional responses), their implications for predator populations, and the temporal and geographical scales at which predator and prey interact). Ecosystem models have traditionally simplified nature to relatively few components linked by mathematical functions. Forecasting impacts of climate/global change requires us to take into account not just changes in the functional form of the links but also changes in the component species, as species distributions shift according to their environmental envelopes.

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