Great South Channel

Overview
The Great South Channel is a prominent feature in the bathymetry of the Gulf of Maine; along with the Northeast Channel, it provides an oceanographic connection between the Gulf of Maine and the Northwest Atlantic Ocean. The channel is a transit route for the endangered Northern Right Whale as it migrates between summer and winter habitats.

Surface area (percentage of total)
2,007 mi2 2%

Depth
50 m – 100 m

Bathymetry including key features
The funnel-shaped Channel is wider and deeper at its northern end.1

Substrate
Sediments include gravel pavement and mounds, occasional boulders, sand with ripples generated by storms, and scattered mussel beds.

Relationship to large-scale circulatory patterns of the Gulf of Maine
In general, water flows into the Gulf from the Scotian Shelf and through the Northeast Channel at depth (river discharge during the spring freshet makes up a third source). Outflow occurs through the Great South Channel and mid and surface layers of the Northeast Channel.2,3,4

Information on average (seasonal/annual) oceanographic conditions
The Great South Channel is well mixed due to tidal currents and the existence of a frontal system between Gulf of Maine waters and those of the Continental Slope.5 The front separates the warmer, surface, stratified waters of the Gulf to the north from the cooler, tidally mixed waters south of the front.6

Trawl survey stations

NEFSC Bottom Trawl Survey – Spring

Average number of tows per year: 6
Number of years for which data is available: 36
Range of years for which data is available: 1968-2003

NEFSC Bottom Trawl Survey – Fall

Average number of tows per year: 7
Number of years for which data is available: 41
Range of years for which data is available: 1963-2003

DFO Bottom Trawl Survey

Average number of stations sampled: 5
Number of years for which data is available: 14
Range of years for which data is available: 1986-2001

NEFSC Shrimp Survey

One tow each in 1985 and 1987

NEFSC Scallop Survey

Average number of tows per year: 23
Number of years for which data is available: 26
Range of years for which data is available: 1975-2003

NEFSC Clam and Quahog Survey

Average number of tows per year: 1
Number of years for which data is available: 8
Range of years for which data is available: 1982-1999

ECNASAP standardized trawl records

Average number of tows per year: 16
Number of years for which data is available: 25
Range of years for which data is available: 1970-1994

Whale abundance, distribution and migratory patterns
A portion of the Great South Channel is designated as a "critical habitat area" for the Northern Right Whale, designated as an endangered species by the National Oceanic and Atmospheric Administration. Right whales feed on plankton in the Great South Channel in mid to late spring.

1 NOAA, Undated
2 Xue, et al., 2000
3 Pettigrew, et al., 2005
4 Maine Ecosystem Dynamics Modeling Laboratory, Undated
5 Velntine, 1999
6 NOAA, Undated