[MARMAM] new article on the significance of strandings
helene.peltier at univ-lr.fr
Thu Jan 5 00:47:40 PST 2012
A new article published in Ecological Indicators is now
THE SIGNIFICANCE OF STRANDING DATA AS INDICATORS OF
CETACEAN POPULATION AT SEA: MODELLING THE DRIFT OF CETACEAN CARCASSES.
Authors: H. Peltier, W. Dabin, P. Daniel, O. Van Canneyt, G. Dorémus,
M. Huon, V. Ridoux.
Contact: hpeltier at univ-lr.fr
Stranded marine mammals are an important source of information and
biological samples on cetacean population. Nevertheless, collecting
stranding data remains opportunistic and its representativity must be
improved, both qualitatively and quantitatively. Drifts of small
cetaceans found by-caught in fishery observation projects and
subsequently released dead with a numbered tag fitted to the tail fluke
were predicted by using the _Météo-France_ drift model MOTHY and allowed
us to assess the proportion of dead dolphins recovered by volunteers of
the French stranding network. Only 8% of dolphins were recovered ashore.
The spatial representativity of strandings was assessed by performing
back-calculation of carcass drift with the same model in order to map
the likely origin of stranded cetaceans. As a first step, external
visual criteria of time-after-death (supposed to be equivalent to drift
duration) were obtained from series of photographs of dead small
cetaceans maintained in a floating cage for 40 days and from tagged
by-caught dolphins recovered stranded after a drift in real condition.
Then, pictures of 242 stranded common dolphins (_Delphinus delphis_)
were used to establish the average distribution of dolphin
time-after-death in this area. Finally, 40 days-long reverse drifts of
the 829 common dolphins recorded in the winter months of 2004 to 2009
were weighted by the modelled distribution of time-after-death in order
to map the areas of likely origin. It appeared that most stranded common
dolphins recorded along the French Atlantic coast originated from the
continental shelf, mostly in the south of the Bay of Biscay. These
results open new perspective on the use of stranding data and biological
samples as sources of indicators in monitoring strategies.
strandings, Indicators, common dolphins_ Delphinus delphis_, harbour
porpoises _Phocoena phocoena_, drift model, stranding rate.
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