[MARMAM] New publication: Trends of harbour porpoise density, southern North Sea
peschko at ftz-west.uni-kiel.de
Sun Jul 19 12:57:23 PDT 2015
We are pleased to announce the following paper:
Peschko, V., Ronnenberg, K., Siebert, U., Gilles, A. (2016). Trends of
harbour porpoise (Phocoena phocoena) density in the southern North Sea.
Ecological Indicators 60: 174-183, DOI 10.1016/j.ecolind.2015.06.030
In the southern North Sea, harbour porpoise occurrence increased in recent
years after a phase of low abundances during earlier decades. Only very few
studies on porpoise presence in the southern German North Sea exist so far.
As anthropogenic activities will strongly increase in this part of the North
Sea during the next years it is most important to assess population level
effects. This study focuses on the analysis of temporal and spatial trends
in porpoise density in this area of recent change. Dedicated aerial
line-transect distance sampling surveys were conducted in the southern
German North Sea between May 2002 and June 2013 to assess porpoise density
and distribution. Statistical inferences on porpoise population trends were
made using a Markov Chain Monte Carlo (MCMC) technique. Two approaches were
chosen to test for a trend in porpoise density and an additional model
focused on the change in density of calves. During 55,820 km of survey
effort 4377 porpoises including 140 calves were recorded. A significant
effect of increasing spatial aggregation from the lower density areas in the
south-eastern German Bight to hot spot areas in the western parts was
detected. For the western part of the study area a significant increase in
porpoise density between 2002 and 2013 was detected. Seasons were
significantly different with highest porpoise density in spring and
successively decreasing densities in summer and autumn. From 2008 onwards
high densities were also observed in summer. Calf density increased during
the study period and was significantly higher in the west. On the basis of
this extensive and unique data set on porpoise occurrence in the southern
German North Sea the findings clearly show that especially the south-western
German North Sea serves as habitat of increasing importance for porpoises
throughout the last decade. Definite reasons still remain unresolved.
Changes in prey abundance or less favourable conditions in other areas could
be important factors, which may also have caused a southward shift from high
density areas in northern waters. On this baseline, further integrative
approaches might lead to a sound understanding of the effect of
anthropogenic activities on the future development of porpoise populations.
It can be downloaded for free until 05.09.2015:
You can also contact me peschko at ftz-west.uni-kiel.de
<mailto:peschko at ftz-west.uni-kiel.de> for a pdf.
Research and Technology Centre Westcoast
University of Kiel
Tel: +49(0)4834 604-250
Fax: +49(0)4834 604-119
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