10 MARINE MAMMALS AND SEA TURTLES - Hebron Project

Hebron Project Comprehensive Study Report
Marine Mammals and Sea Turtles
2008). There are two stocks of sei whales recognized in the Northwest
Atlantic: a more well-known Nova Scotia stock whose distribution extends
from the northeast United States to southern Newfoundland, and a Labrador
Sea stock (Waring et al. 2009). The Nova Scotia stock is estimated to contain
207 individuals, but there is no current population estimate for the Labrador
Sea stock (Waring et al. 2009). It is unclear to which population animals
occurring off eastern Newfoundland belong.
Sei whales tend to be found in pelagic regions, most often in areas with steep
bathymetric relief like continental shelf breaks, seamounts, canyons, or
basins near banks and ledges (Kenney and Winn 1987; Gregr and Trites
2001). Sei whales typically occur alone or in groups of two to five, and
females are larger than males (Jefferson et al. 2008). Although they
sometimes consume small fish, primary prey consists of euphausiids and
copepods (Flinn et al. 2002).
Mitchell and Chapman (1977) hypothesized that sei whales in the Northwest
Atlantic are migratory, moving from spring feeding areas on or near Georges
Bank to the Scotian Shelf in June and July, eastward to Newfoundland and
the Grand Banks in late summer, back to the Scotian Shelf in fall, and
offshore and south during winter. These authors estimated a minimum stock
size of 870 individuals, based on mark-recapture data from the 1960s to
1970s. In the Jeanne d‘Arc Basin, there has been one confirmed sei whale
sighting and one possible sighting (either a sei or fin whale) (Table 10-4).
However, sei whales were encountered several times in the Orphan Basin
(Moulton et al. 2005,2006; Abgrall et al. 2008b).There were 11 sei whale
sightings reported in the DFO cetacean sightings database in the Offshore
Study Area (Table 10-6). The available information suggests that sei whales
are present during summer and fall months, but are likely uncommon, in the
Offshore Study Area.
There is little information on the presence of sei whales in Trinity Bay, but the
sei whale tends to be a more pelagic species and is not typically reported in
coastal Newfoundland. In addition, it is often difficult to differentiate between
sei whales and fin whales in the field. It is possible that some reports of fin
whales could actually be sei whales. A live sei whale was reported stranded
off Catalina on August 11, 2008 and subsequently died (Ledwell and
Huntington 2009). There were no sightings of sei whales reported in the DFO
cetacean sightings database in the Nearshore Study Area (Table 10-5).
Given the information available, sei whales are expected to be rare in the
Nearshore Study Area throughout the year.
Minke Whale
The smallest of the baleen whales, minke whales are cosmopolitan in
distribution and can be found in polar, temperate, and tropical waters
(Jefferson et al. 2008). Four populations are recognized in the North Atlantic:
the Canadian east coast, west Greenland, central North Atlantic, and
northeastern North Atlantic stocks (Waring et al. 2009). An estimated 3,312
individuals occur in the Canadian east coast stock, which ranges from the
10-16 June 2010