Geoscience Reference
In-Depth Information
breeding and whelping areas, to which they show a high degree of fidelity, the seals of all ages undertake ex-
tensive wanderings around, and in some cases outside, the gulf.
Hooded seals also occur in much smaller breeding units than harp seals. Hooded seals are larger than both
harp and gray seals, growing to 2.7 meters (9 feet) and 400 kilograms (900 pounds). Their most distinguishing
feature is the large nasal apparatus of the males. Part of the nasal cavity is enlarged to form a hood, which runs
from the crown to the upper lip and overhangs it in older animals. When angered, the seals can enlarge this
cavity, and they also can inflate the nasal membrane, which appears as a red balloon-like sac protruding from
the nostril. They congregate near the Magdalen Islands, where they have a one-month breeding season, spend-
ing most of their time on the pack ice, before migrating toward Greenland in early May. It is unclear whether
they feed while in the gulf, but if they do, they probably exploit deepwater species such turbot, cod, and red-
fish.
IN SUMMER, THE
Magdalen Shallows become a warm-water refuge. During the warming period that followed
glaciation, warm water extended northwards along the coast as far as the Gulf of St. Lawrence, and with it spe-
cies more characteristic of the Virginian province to the south of Cape Cod. One of the species that thrived
north of its current distribution was the American oyster. Today it survives in the Maritime Provinces only in
shallow water areas of the Gulf of St. Lawrence, with the exception of a pocket in the Bras d'Or Lakes. Extinct
populations—known from fossil shells in the Minas Basin, on Sable Island, and in the Magdalens—speak to
its formerly more widespread distribution, and large pre-colonial middens along the Maine coast confirm its
former abundance there. Oysters can tolerate low winter temperatures, as is the case in the gulf, but require
warm summer temperatures, up to 32°C (90°F), to breed and propagate. Because the southern gulf is shallow,
the waters are warm enough in summer to support oysters. They can feed and grow at temperatures below
what it requires to produce eggs and sperm and therefore may only produce spawn during the summer. In
northern waters, below 4° to 5°C (40°F), they lie dormant.
The oyster's reproductive behavior is one of the most remarkable in the animal kingdom. It spawns first as a
male and later switches to being female and produces eggs. It may make this sex change during successive
seasons. As a female, it may produce as many as 100 million eggs. The oyster larvae, known as “spat,” settle
to the bottom, where they attach themselves to any hard surface, often other oyster shells, which in time pro-
duce an oyster bed. The oyster has a byssus gland on its foot that discharges a sticky secretion, cementing it to
the substrate. It always lies on its left shell, which is more bowl-shaped, and thus keeps its edge raised above
the bottom, preventing it from being fouled with silt.
IN JUNE
1833, almost three centuries to the year after Cartier first reconnoitered the remote, flat-topped Bird
Islands in the center of the gulf, John James Audubon recorded his approach to the islands, which at first ap-
peared to him “to be covered with snow several feet deep.” It was, however, a flurry of gannets. “I rubbed my
eyes, took up my glass,” wrote Audubon, “and saw that the strange dimness of the air was caused by innumer-
able birds, whose white bodies and black-tipped pinions produced a blended tint of light gray. When we ad-
vanced within a half mile, this magnificent veil of floating gannets, plainly seen, now shot upwards into the
sky, then descended as if to join the feathered masses below, and again veered off to either side and swept over
the surface of the ocean.” Today, the gulf remains a place of abundance and wonder.
