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The occurrence of the colonial ascidian Didemnum sp. on Georges Bank gravel habitat: ecological observations and potential effects on groundfish and scallop fisheries

Journal of Experimental Marine Biology and Ecology

By:
, , , , , and
DOI: 10.1016/j.jembe.2006.10.038

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Abstract

The colonial ascidian Didemnum sp. is present on the Georges Bank fishing grounds in a gravel habitat where the benthic invertebrate fauna has been monitored annually since 1994. The species was not noted before 2002 when large colonies were first observed; and by 2003 and 2004 it covered large areas of the seabed at some locations. The latest survey in 2005 documented the tunicate's presence in two gravel areas that total more than 67 nm2 (230 km2). The affected area is located on the Northern Edge of the bank in United States waters near the U.S./Canada boundary ( Fig. 1). This is the first documented offshore occurrence of a species that has colonized eastern U.S. coastal waters from New York to Maine during the past 15–20 years ( U.S. Geological Survey, 2006). Video imagery shows colonies coalescing to form large mats that cover more than 50% of the seabed along some video/photo transects. The affected area is an immobile pebble and cobble pavement that lies at water depths of 40 to 65 m where strong semidiurnal tidal currents reach speeds of 1 to 2 kt (50–100 cm/s). The water column is mixed year round, ensuring a constant supply of nutrients to the seabed. Annual temperatures range from 4 to 15 °C ( Mountain and Holzwarth, 1989). The gravel areas are bounded by sand ridges whose mobile surfaces are moved daily by the strong tidal currents. Studies commenced here in 1994 to characterize the gravel habitat and to document the effects of fishing disturbance on it ( Collie et al., 2005).

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The occurrence of the colonial ascidian Didemnum sp. on Georges Bank gravel habitat: ecological observations and potential effects on groundfish and scallop fisheries
Series title:
Journal of Experimental Marine Biology and Ecology
DOI:
10.1016/j.jembe.2006.10.038
Volume
342
Issue:
1
Year Published:
2007
Language:
English
Publisher:
Elsevier
Contributing office(s):
Coastal and Marine Geology Program
Description:
3 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Experimental Marine Biology and Ecology
First page:
179
Last page:
181
Number of Pages:
3
Country:
United States
State:
Massachusetts
Other Geospatial:
Georges Bank