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
è http://gsm-ev.de/en/veroffentlichungen/
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 ×
Distribution
********************************************
Philip
Loos
Society
for the Conservation
of Marine Mammals (GSM)