Dear colleagues,
I am glad to inform you that a new article is now available online:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0062180
The Stranding Anomaly as Population Indicator: The Case of
Harbour Porpoise Phocoena phocoena in North-Western
Europe.
Helene Peltier, Hans J. Baagøe,Kees C. J. Camphuysen,Richard
Czeck,Willy Dabin,Pierre Daniel,Rob Deaville,Jan Haelters,Thierry
Jauniaux,Lasse F. Jensen,Paul D. Jepson,Guido O. Keijl,Ursula
Siebert,Olivier Van Canneyt,Vincent Ridoux
Abstract:
Ecological indicators for monitoring strategies are expected to
combine three major characteristics: ecological significance,
statistical credibility, and cost-effectiveness. Strategies based on
stranding networks rank highly in cost-effectiveness, but their
ecological significance and statistical credibility are disputed.
Our present goal is to improve the value of stranding data as
population indicator as part of monitoring strategies by
constructing the spatial and temporal null hypothesis for
strandings. The null hypothesis is defined as: small cetacean
distribution and mortality are uniform in space and constant in
time. We used a drift model to map stranding probabilities and
predict stranding patterns of cetacean carcasses under H0
across the North Sea, the Channel and the Bay of Biscay, for the
period 1990–2009. As the most common cetacean occurring in this
area, we chose the harbour porpoise Phocoena phocoena for
our modelling. The difference between these strandings expected
under H0 and observed strandings is defined as the
stranding anomaly. It constituted the stranding data series
corrected for drift conditions. Seasonal decomposition of stranding
anomaly suggested that drift conditions did not explain observed
seasonal variations of porpoise strandings. Long-term stranding
anomalies increased first in the southern North Sea, the Channel and
Bay of Biscay coasts, and finally the eastern North Sea. The
hypothesis of changes in porpoise distribution was consistent with
local visual surveys, mostly SCANS surveys (1994 and 2005). This new
indicator could be applied to cetacean populations across the world
and more widely to marine megafauna.
All the best
Helene Peltier
--
Hélène PELTIER -PhD
Observatoire PELAGIS UMS 3462
Université de La Rochelle-CNRS
5, allées de l'océan
17000 La Rochelle, France
hpeltier@univ-lr.fr
+33 (0) 16 49 67 82 /+33 (0) 6 82 74 08 41