Teilmann, J., Sveegaard, S., Dietz, R., Petersen, I.K., Berggren, P. & Desportes, G. 2008: High density areas for harbour porpoises in Danish waters. National Environmental Research Institute, University of Aarhus. 84 pp. – NERI Technical Report No. 657.

 

Summary

Designating protected areas for harbour porpoises implies identifying areas of high porpoise density with particular focus on the distribution during the breeding season. This report collates all relevant data on movements and density of the harbour porpoises in Danish and adjacent waters in order to identify key habitats, i.e. areas with high density, for harbour porpoises in Denmark  that may be useful when designating protected areas under the Habitats Directive.

 

Comprehensive data from satellite tracking, aerial and ship surveys as well as acoustic surveys from ship have been collected from 1991 to 2007 in Danish waters. In this study the primary source of data for identifying key habitats is satellite tracking of 63 harbour porpoises in the period 1997-2007. The only major areas that were not covered by the tagged animals were the Southern North Sea and the waters around Bornholm  . In the Southern North Sea , data from aerial surveys was used to identify high density areas. Data from the area around Bornholm were too limited to determine harbour porpoise distribution and density. In northern North Sea and Inner Danish Waters acoustic ship surveys and aerial surveys were used as an independent method to confirm the presence of the high density areas found by analysis of the satellite tracking data.

 

The high density areas are described separately based on the management units proposed based on previous population structure studies. Four management areas are proposed but only in three areas there are data enough to identify high density areas. The three areas are: 1. The Inner Danish Waters (south of Læsø in Kattegat) through the belts and Øresund to the Western Baltic (west of Bornholm  ). 2. The Skagerrak/northern North Sea/northern Kattegat (north of Læsø and north of Ringkøbing), 3. The southern North Sea (south of Ringkøbing). Each high density area is ranked based on our current knowledge of population structure, density, seasonal variation in distribution and other relevant information. The rankings are defined as 1=high importance, 2=medium importance and 3=lower importance.

 

Sixteen areas were found to have high density and were ranked as follows for the three areas: Inner Danish Waters: Northern Little Belt (2), southern Little Belt (1), southern Samsø Belt (2), northern Samsø Belt (3), Northern Øresund (1), Store Middelgrund (2), Kalundborg Fjord (1), Great Belt (1), Smålandsfarvandet (3), Flensborg Fjord (1), Fehmarn Belt (1), Kadet Trench (2). Northern North Sea: Tip of Jylland (1), Skagerrak  (along Norwegian Trench, 2). Southern North Sea : Horns Rev (1), German Bight (1).

 

Full report in pdf (7,188kB)