The Davis Strait - DCE - Nationalt Center for Miljø og Energi

140
4.8.5 Toothed whales (Odontoceti)
Eight species of toothed whales possibly occur in the assessment area: longfinned
pilot whale (Globicephala melas), white-beaked dolphin (Lagenorhynchus
albirostris) harbour porpoises (Phocoena phocoena), narwhal (Monodon
monoceros) beluga whale (Delphinapterus leucas), killer whale (Orcinus orca),
sperm whale (Physeter macrocephalus) and northern bottlenose whale (Hyperoodon
ampullatus). As for the baleen whales, a change in prey distribution or
ice coverage, e.g. due to climatic changes, is likely to cause a change in the
toothed whale distribution. The distribution of e.g. the beluga whale depends
largely on the distribution of ice coverage, the whale staying close to
the edge of the pack ice and moving further north or further west, further
offshore if any loosening in the pack ice occurs (Heide-Jørgensen et al. 2009).
Hence, changes in ice coverage and in temperature may change the distribution
of certain species of toothed whales.
Sperm whale, Physeter macrocephalus
Sperm whales are the largest of the toothed whales and reach lengths of 18
m and weights of 50 tonnes. Although they are found in all oceans, the species
display sexual segregation where females and calves reside in tropical
and sub-tropical waters year round, while males inhabit high latitude feeding
grounds with occasional visits to their low latitude breeding grounds
(Best 1979). Sperm whales prey on a variety of deep-sea fish and cephalopods.
Stomach samples from 221 sperm whales caught between Iceland and
Greenland showed that benthic or pelagic fish (especially the lumpsucker,
Cyclopterus lumpus) constituted the majority of the diet but also oceanic cephalopods
were an important part of the sperm whale diet in this area (Martin &
Clarke 1986). Stomach content of sperm whales caught in West Greenland
contained exclusively fish (Kapel 1979).
The abundance of sperm whales in Greenland and within the assessment area
is not known but sperm whales are encountered on a regular basis (e.g.
Larsen et al. 1989). Sperm whales are found mainly in deep waters along the
continental slope, but they can also be seen in deep fjords and have been observed
in the Nuuk fjord system, within the assessment area, in both 2009
and 2010 (GINR, unpubl. data). Echolocation clicks of sperm whales have also
been recorded close to the West Greenlandic continental shelf in the Davis
Strait (GINR, Unpubl.). Male sperm whales feed both at shallow depths of
approximately 117 m and at the sea bottom at depths down to 1860 m, showing
that male sperm whales have flexible feeding habits (Teloni et al. 2008).
Sperm whales are expected to use the assessment area during ice-free periods
in suitable habitat, such as deep-sea waters close to continental slopes
and underwater canyons with abundance of cephalopod or fish prey.
The International Whaling Commission considers the North Atlantic sperm
whales as belonging to a single population (Donovan 1991), which is further
supported by genetic analyses (Lyrholm & Gyllensten 1998). On a global
scale sperm whales are categorised as vulnerable (IUCN 2008), but due to
poor documentation of sperm whale abundance around Greenland the species
is listed as not evaluated on the Greenland Red List (Boertmann 2007).
Long-finned pilot whale, Globicephala melas
The long-finned pilot whale occurs in temperate and sub-polar zones, but is
according to Greenlandic catch statistics occasionally also found as far North
as Upernavik (DFFL, unpubl. data). In the USA, long-finned pilot whales
have seasonal movements that appear to be dictated by their main prey, the