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You are here: Home / Associated publications / Belgian Journal of Zoology / Bibliographic References / The harbour porpoise Phocoena phocoena in the Belgian part of the North Sea: trends in abundance and distribution

Jan Haelters, Francis Kerckhof, Thierry Jacques and Steven Degraer (2011)

The harbour porpoise Phocoena phocoena in the Belgian part of the North Sea: trends in abundance and distribution

BELGIAN JOURNAL OF ZOOLOGY, 141(2):75-84.

The harbour porpoise Phocoena phocoena is currently common in the Belgian part of the North Sea (BPNS), after decades of virtual absence. This article describes the results of aerial surveys to assess its distribution and density in Belgian waters, in concert with the first results of tests with passive acoustic monitoring devices (Porpoise Detectors - PoDs), and a basic analysis of strandings. The strandings data over four decades clearly demonstrate an increase of harbour porpoises in the BPNS, with only few stranded animals between 1970 and 1997 (0 to 6 per year), increasing numbers between 1998 and 2004 (8 to 40 per year), and even higher numbers between 2005 and 2009 (62 to 94 per year). The combined results of aerial surveys, strandings monitoring and tests with passive acoustic monitoring reveal a seasonal pattern, with harbour porpoises being abundant from February to April, and more scarce from May to January. Average densities in 2008 and 2009, as estimated by aerial monitoring covering most of the BPNS (with the exclusion of the nearshore 5 km strip), ranged from 0.05 animals per km(2), or in total less than 200 animals in an area equivalent to the BPNS in August 2009, to 1.01 animals per km(2), or in total almost 3,700 animals in an area equivalent to the BPNS during April 2008. In the first quarter of the year porpoises occur throughout the BPNS, including territorial waters (12 mile zone), whereas they are restricted to more offshore and northerly waters later in the year. Erratic invasions in the BPNS however blur general seasonal spatio-temporal patterns, which complicates our understanding of spatial distribution and migration.

Harbour porpoise; Phocoena phocoena; Belgian part of the North Sea; abundance; seasonal distribution
BJZ

ISSN 2295-0451 (online version)
ISSN 0777-6279 (printed version)
impact factor 2015: 0,87.

Editor-in-Chief:
Prof. Dr. Isa Schön
Royal Belgian Institute of Natural Sciences
Vautierstraat 29
1000 Brussels, Belgium

 



1863-1903
Annales de la Société malacologique de Belgique
 
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Belgian Journal of Zoology