Geoscience Reference
In-Depth Information
This anemone (left) and sea cucumber (right) are part of the cornucopia of bottom-dwelling creatures common to the
Gulf of Maine.
The shallowness of Georges—in some places, such as Cultivator and Georges Shoals, it is only 3.65 meters
(12 feet) deep—accounts in part for its productivity. Sunlight penetrates to the bottom of the bank, and tides
and winds acting over the shallow banks stir the waters, causing vertical mixing that keeps the nutrients avail-
able. Furthermore, the clockwise gyre over the bank is a partially closed circuit, entraining the nutrients and
plankton—and the fish eggs and larvae—for longer periods, thus boosting and sustaining productivity, estim-
ated at four times that of the legendary Grand Banks off Newfoundland. Phytoplankton growth is fueled not
only by nutrients supplied to the bank from the deep waters surrounding it but also by so-called regenerated
nutrients, that is, those excreted from animals and bacteria. So the abundant life on the bank is, in part, a
product of itself, or specifically, of its waste products, which are taken up and recycled in the system.
Divvying Up the Riches
Generally speaking, the Gulf of Maine is a meeting place for species native to areas north and south of it. On
Georges Bank, for example, three biogeo-graphic species groups mingle: Labrador species in the deep water,
Acadian species at the intermediate depths, and Virginian species at the shallow depths on top of the bank. In
summer, bluefin tuna pass through the gulf on spectacular migrations spanning the North Atlantic, and their
smaller cousins, mackerel, leave the deep water off the Virginian capes to pass through the Gulf of Maine.
Other southerly species, such as bluefish, butterfish, menhaden, and summer flounder, also come north to the
bank in summer to feed and mix with northerly types such as the major groundfish species—cod, pollack, had-
dock, halibut, redfish, plaice, and argentine—which spawn on Georges Bank itself. Only two migrants from
the north frequent gulf waters: Atlantic salmon returning from their Arctic feeding grounds to their natal
rivers, and capelin, a subarctic member of the smelt family. Mixed in with these typically southern and north-
ern species are more ubiquitous species that are regularly found in waters both to the north and south of the
banks, namely, squid, lobster, scallop, herring, red hake, silver hake, swordfish, and yellowtail flounder,
among others.
Fish are found in markedly different parts of the Gulf of Maine during different parts of the year. Pelagic
(near-surface) fishes, like herrings, seem to be more common along the eastern parts of the coast and off New
