The purpose of the cruise is two fold: first to study the importance of the prized tilefish burrow as a lobster habitat, and second to evaluate the extent and style of sediment reworking by organisms on the outer shelf.
Location
New England Shelf, Middle Grounds, Block Canyon to Atlantis Canyon, United States, North America, North Atlantic;
Summary
This study was conducted over the open shelf in the Middle Grounds, the general area between Block and Atlantic Canyons. The specific site was chosen based on our extensive sidescan sonar surveys during 1984. We completed 14 dives, including one at night. Of these, Lance Stewart conducted one to test NURP-designed gear and another in an attempt to help URI scientists locate a missing scientific package. Most dives were centered around 725 ft. (690-840 ft.) in an area with numerous large tilefish burrows (approximately 10 ft. diameter) and abundant lobsters. Two dives immediately inshore in more shallow water (345-385 ft.) found tilefish burrows but no lobsters. We observed 85 lobsters during these dives. Most of these were moving over the open bottom as if they were taking part in the inshore migration. Many others were found in tilefish burrows and frequently lobsters and tilefish were observed simultaneously in the same vertical burrow. These lobsters usually were in larger alcoves in the upper one meter of the tilefish burrows. The shape of these smaller burrows suggested that they were dug by lobsters. Some lobsters were observed in abandoned tilefish burrows, particularly those in which the subsurface clay was still exposed. Other lobsters were observed in shallow bowl-shaped depressions as observed by other researchers. The bowl-shaped depressions were apparently of their own construction. The single night dive verified earlier observations in previous years in which we observed a marked shift in the fish fauna relative to dives during the day. These data along with extensive 35 mm and video film are still being analyzed. Observations from the DELTA submersible, bottom photography, and sediment sampling comprise the bulk of our work. Some pingers were placed for burrow location at a later date.
Info derived
Samples and chemical analysis; Morphology;
Comments
Updated 02/25/09 by A. Orton for D. Twichell. Data Curator: Ken Able.
Project = Habitat Ecology of Offshore Populations of American Lobster, Habitat Ecology of Offshore Populations of American Lobster
