The common bottlenose dolphin (Tursiops
truncatus) is one of the best known of the cetaceans
(whales, dolphins, and porpoises); a cosmopolitan species
found in the coastal and offshore waters of the world’s
temperate to tropical seas. As in most other dolphin
species, T. truncatus are social animals.
While the typical social group consists of 10-20
individuals, larger aggregations can be found.
In the North Atlantic, during the summer T.
truncatus can typically be found offshore as far
north as Nova Scotia; and inshore, typically south of Long
Island.
In the waters of the Western North Atlantic two morphotypes,
the coastal morphotype and the offshore morphotype have been
identified. These morphotypes differ not only in their
distribution (coastal morphotypes, in warmer, shallower near
shore waters less than 7.5 km from shore; offshore
morphotypes, in deeper, cooler waters greater than 35 km
from shore); they also differ morphologically, differ in
their diet, differ in their typical parasite loads, and they
differ genetically (different mitochondrial DNA haplotypes).
It is thought that the coastal morphotype is distributed
continuously along the Atlantic coast, from south of Long
Island, around the Florida peninsula, and along the coast of
the Gulf of Mexico. Coastal T. truncatus from the
Gulf of Mexico and the Western North Atlantic are known to
belong to two different stocks, based on mitochondrial DNA
differences. It wasn’t until recently that an accurate
delineation of the stock structure of the Western North
Atlantic coastal morphotype had been developed. According to
the NOAA Fisheries 2010, Stock Assessment Report (SAR), the
Western North Atlantic coastal morphotype is now considered
to be composed of “a complex mosaic of coastal bottlenose
dolphin stocks.” NOAA Fisheries now recognizes 5 coastal
morphotype stocks: the Northern Migratory Coastal stock, the
Southern Migratory Coastal stock, the South Carolina/Georgia
Coastal stock, and the Northern Florida Coastal and Central
Florida Coastal stocks. The coastal bottlenose dolphins of
NY and New England are members of the Northern Migratory
Coastal stock.
While the coastal morphotype had occasionally been seen
north of New Jersey, including a small group seen and
photographed by me in July 2007 near Cape Anne, MA,
sightings of large groups were rare. In late June 2009, a
large group of bottlenose dolphins was sighted near Glenn
Cove, NY, and through July 2009, a group of 200 coastal
morphotype bottlenose dolphins was sighted in elsewhere in
Western Long Island Sound (Cold Spring, Huntington,
Northport, Hempstead, Oyster Bay, Smithtown and Rye). Over
the next few weeks the group (or others like it) were seen
further east in the Sound, and ultimately were sighted and
photographed near Montauk Point in early August 2009 and
again in early September 2009.Follow @CRESLI_Inc
