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Seasonal habitat-based density models for harbour porpoises (subproject DEPONS)


Project leader: Prof. Prof. h. c. Dr. Ursula Siebert
Scientific work: Dr. Anita Gilles, Sacha Viquerat
Project term: Juni 2014 until November 2014
Sponsorship: Aarhus Uni/Vattenfall
Cooperation: IMARES Wageningen Institute for Marine Resource & Ecosystem Studies
Royal Belgian Institute of Natural Sciences (RBINS)
Aarhus University, Department of Bioscience

Project description

The aim of this subproject within the DEPONS project (Disturbance Effects on the Harbour Porpoise Population in the North Sea;, was to identify areas in the eastern, central and southern North Sea with high porpoise densities and to predict the seasonal distribution and density of porpoises (Gilles et al., in review). Therefore, an unprecedented set of survey data for the harbour porpoise (Phocoena phocoena) has been aggregated to develop seasonal habitat-based density models for the North Sea. The datasets were collected over nine years (2005–2013) and during three seasons in the UK (SCANS II, Dogger Bank), Belgium, the Netherlands, Germany and Denmark, by means of dedicated aerial surveys for harbour porpoises using standardised line-transect survey methods and incorporating correction factors for missed animals on the transect line.

These data have never before been analysed jointly. Generalized additive models of porpoise density were fitted to 157,000 km of on-effort survey data with 14,360 sightings of porpoise groups. We developed the models incorporating near real-time remote sensing data to identify dynamic mesoscale oceanographic features that are often observed to be hotspots for marine mammals. The selected predictors included static and dynamic variables, such as depth, distance to coast and to sandeel (Ammodytes spp.) grounds, sea surface temperature (SST), proxies for fronts and day length.

The season-specific population density maps could be used to assist the EU Habitats and Marine Strategy Framework Directives in effectively assessing the conservation status of harbour porpoises. Moreover, the results can facilitate the identification of regions where human activities and disturbances are likely to impact the population. This is especially relevant for marine spatial planning, which requires accurate fine-scale maps of species distribution to assess risks of increasing human activities at sea.

Results of this study will be used as input in individual-based models (IBMs) within the DEPONS project (University of Aarhus), where population dynamics in the North Sea can be predicted based on simulated animals that move in the landscape in a realistic manner.

Contact person

University of Veterinary Medicine Hannover, Foundation Institute for Terrestrial and Aquatic Wildlife Research Werftstr. 6 25761 Büsum


Sacha Viquerat

Tel.:+49 511 856-8172

Fax.:+49 511 856-8181


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Stiftung Tierärztliche Hochschule Hannover
Institute for Terrestrial and Aquatic Wildlife Research
Werftstr. 6
25761 Büsum
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