Part
2, Sec. 2B2e
Sanctuary
Resources - Natural Resources
Sea
Turtles
e.
Sea Turtles
Although
four species of sea turtles have been recorded in Gulf of Maine
waters, only two, the leatherback and the Atlantic ridley, are
seen with any regularity. All species are currently listed as
either threatened or endangered.
Atlantic,
or Kemp's ridley (Lepidochelys kempi). Atlantic
ridleys are observed in waters off Massachusetts as juveniles,
having either swum or drifted north in the Gulf Stream from
hatching areas off the southern coast of Mexico. Juvenile ridleys
generally measure 10" to 12", and weigh around seven pounds.
Southern New England waters are important feeding grounds for
ridleys and are thus considered important habitat for this endangered
species. Each fall (generally between November and January),
as Cape Cod Bay water temperatures decline, a number of ridleys
regularly strand on Cape Cod due to cold-stunning (Prescott,
1986). Cold-stunning occurs when water temperatures fall below
12 degrees C (57 degrees F), and turtles are unable to swim
or digest food. Between 1977 and 1987, a total of 115 juvenile
ridleys were found stranded on Cape Cod beaches (Danton and
Prescott, 1988).
Leatherback
(Dermochelys coriacea). The endangered leatherback
is a regular summer visitor to the waters around Cape Cod, the
Gulf of Maine, and Nova Scotia. This is the only species of
sea turtle that colonizes cold waters for feeding activities,
which include jellyfish (notably the lion's mane jellyfish),
comb jellies, salps, and other jelly organisms abundant in these
waters during the summer. The largest and heaviest of all extant
reptiles, leatherbacks may grow to ll feet in length and weigh
up to 1,900 pounds. Turtles observed in the area between Cape
Cod and Newfoundland are generally single, mature animals, frequently
measuring more than six feet in length and weighing over 1,000
pounds. Of all sea turtles, leatherbacks appear to migrate the
farthest in search of summer food; Western North Atlantic leatherbacks
breed anytime between April and November along beaches in Central
and South America (with very occasional nesting activity noted
in southern Florida). Females usually nest only every other
year, during March and April, and may not migrate as far north
as males during breeding years. This may explain why most leatherbacks
observed in the Gulf of Maine are males. Sightings off Massachusetts
are most frequent during late summer (July through September).
The turtles usually first appear in the Gulf of Maine between
May and June, and are most frequently seen in the Gulf's southerly
coastal waters. In the autumn, the turtles move further offshore
and begin their migration south for the winter (Payne, et al.,
1986).
The
physiological adaptations of leatherbacks to pelagic environments
make this species poorly-equipped to deal with obstructions
in shallow waters. Leatherbacks regularly become entangled in
fishing nets and lobster pot lines, situations which are compounded
by this species' inability to either maneuver easily or to swim
backwards. In addition to these problems, leatherbacks have
been reported to die from intestinal blockage following consumption
of plastic bags, which they presumably mistakenly identify as
jellyfish. Collisions with boats also occasionally result in
leatherback mortality.
Loggerhead
(Caretta). Although loggerhead sea turtles are the most
widespread and numerous species along the eastern seaboard,
they are generally absent in shelf waters north of Cape Cod,
including Cape Cod Bay and the Gulf of Maine. Water temperature
is the primary factor in marking Massachusetts as the northern
tolerance limit for this endangered species. Following nesting
activity, loggerheads disperse northward, and there are limited
sightings along outer Cape Cod and the islands during mid-summer
through fall. Occasionally, loggerheads become trapped inside
Cape Cod Bay in late fall and winter, resulting in cold-stunning
and death.
Green
(Chelonia mydas). Juvenile green sea turtles are rare
summertime stragglers as far north as Cape Cod Bay. This endangered
species generally is found in waters warmer than 20 degrees
C.
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