Page 143 - Alderney Regional Environmental Assessment of Renewable Energy: Environmental Report

Alderney Regional Environmental Assessment of Renewable Energy:
Environmental Report
Distribution and Abundance in the English Channel
High densities of common dolphin have been recorded in the western English Channel in
winter with the area appearing to be important for foraging seasonally (Clarke et al ., 2010;
WDCS, 2005; Kiszka et al. 2007; DECC, 2009). Relatively few sightings have been reported in
the eastern English Channel and the North Sea. An estimated abundance of 14,349 common
dolphin were recorded in the Southern North Sea and Channel in 2005 (SCANS-II, 2008).
Based on observations of seasonal patterns in sightings data, common dolphins are thought to
show a general movement into offshore waters beyond the shelf zone (Clarke et al., 2010;
DECC, 2009). The apparent movement into offshore waters during the summer is likely to be
prey-driven. While a large proportion of the population are thought to move into offshore
waters, not all do. Encounter rates during the summer are still quite high off south west
England and parts of the western English Channel. Dietary differences between the population
that remains in on-shelf waters over the summer and the one that moves offshore suggest that
two ecological stocks within the north east Atlantic might occur, a coastal and a neritic stock
(Clarke et al., 2010).
Distribution and Abundance Around the Channel Islands and Cotentin Coast
The Channel Sea Marine Mammal Sighting Network recorded 12 sightings of bottlenose
dolphin in 2010 and 14 sightings in 2011 in the Gulf of St Malo and Normandy coast. Sightings
in both years were widely distributed (GECC, 2011; GECC, 2010).
While common dolphin has sometimes been recorded around the Channel Islands, the species
has a largely offshore distribution, typically where water depths range from 50-150 metres
(Seawatch Foundation, 2007; Baines and Evans, 2012).
Distribution and Abundance Around Alderney
Common dolphin were recorded to the north of Alderney but not further inshore during the
OpenHydro Subsea Tidal Array Installation Seabird and Marine Mammal Monitoring (ARE,
2009; Entec UK Limited, 2007). No common dolphin were recorded in the seabird and marine
mammal baseline survey within the south east region of Alderney commissioned in 2010 by
Alderney Commission for Renewable Energy (Alderney Wildlife Enterprise, 2011).
Risso’s Dolphin (Grampus griseus)
The Risso’s dolphin is widely distributed in tropical and temperate seas of both hemispheres,
occurring in small numbers along the Atlantic European seaboard from the Northern Isles,
South to North West France, the Southern Bay of Biscay, around the Iberian Peninsula and
East into the Mediterranean Sea. Risso’s dolphins generally prefer continental slope regions.
In North West Europe however, Risso’s dolphin appear to be a continental shelf species (Reid
et al. 2003).
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