[MARMAM] Online resources on opportunistic sightings of harbour porpoises in the Baltic Sea
ploos at gsm-ev.de
Tue May 18 13:53:59 PDT 2010
Dear list members,
The following publications have been made available for download lately:
Loos, P., Cooke, J.G., Deimer, P., Fietz, K., Hennig, V., Schütte, H.J.
(2010) Opportunistic sightings of harbour porpoises in the Baltic Sea at
large Kattegat, Belt Sea, Sound, Western Baltic and Baltic Proper.
AC17/Doc.5-05(P). ASCOBANS, Bonn
Loos, P. (2009) Opportunistic sightings of harbour porpoises in the Baltic
Sea at large Kattegat, Belt Sea, Sound, Western Baltic and Baltic Proper.
Bachelor thesis, University of Hamburg, Germany
ABSTRACT: In order to supplement current knowledge on trends in harbour
porpoise (Phocoena phocoena) occurrence, incidental sightings of harbour
porpoises have been collected in the Baltic Sea. During the seasons 2003 -
2008 a total number of 5561 sightings were collected and saved for further
analysis. Seasonal variation of harbour porpoise sightings, group size and
group composition were examined. Sightings with juveniles (n = 539) were of
special interest and were therefore analysed separately. Possible calving
and nursing grounds (proposed by Koschinski, 2002) have been mapped together
with all juvenile sightings in order to see if there are any notable
clusters of juvenile sightings within these (or other) areas. To investigate
seasonal and spatial trends in porpoise densities, sightings were divided
into five different geographical and five different temporal subsets.
Corresponding indices of relative density were computed using an adaptation
of an effort correction method, described by Cooke (1984). Obtained results
indicate that the seasonal distribution of porpoise sightings largely
reflects the activity patterns of water sports enthusiasts. The group size
was relatively small as in most sightings one single individual was
observed. Very few reports refer to sightings of more than five individuals.
Sightings with juveniles were found in nearly all proposed calving and
nursing grounds, and three additional areas with a cluster of juvenile
sightings could be identified. Harbour porpoise densities were found to
severely decline from (north-) west to (south-) east in the western Baltic
Sea. A seasonal variation in porpoise densities was detected at the end of
summer with dropping densities in August and September. The study shows that
incidental sightings of non-professional observers do have scientific value
and provide data for various analyses concerning porpoise distribution,
occurrence, and density.
KEY WORDS: Harbour porpoise × Incidental sightings × Relative density ×
Society for the Conservation
of Marine Mammals (GSM)
ploos at gsm-ev.de , www.gsm-ev.de
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