Home News Local news SONAR MAPPING OF OCEAN FLOOR SET OVER 5 DAYS

SONAR MAPPING OF OCEAN FLOOR SET OVER 5 DAYS

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Feb. 15, 2002 – A U.S. Environmental Protection Agency survey vessel and V.I. Fish and Wildlife Division personnel will be conducting ultrasonic ocean-floor mapping Saturday through Wednesday south of St. Thomas and St. John.
Planning and Natural Resources Department officials are advising fishermen, recreational boaters and divers to avoid the designated areas:
– A one-square-mile artificial reef area off Saba Island south of St. Thomas, at 18"17.5'N latitude and 64"59.0'W longitude.
– A large area more than three miles south of St. John that includes the south shelf edge and some portions of the area beyond the edge.
PNR officials also are urging fishermen to remove traps in both areas for the five days. Divers accompanying the EPA vessel R/V Anderson will try to untangle lines, but the best way to avoid any losses will be to pull the traps, a release stated.
The ocean bottom, or benthic, mapping survey complements the National Oceanic and Atmospheric Administration survey some years ago of St. Thomas and St. John near-shore and shallow waters.
PNR and its Fish and Wildlife Division are grateful to the EPA for making the current survey possible, Barbara Kojis, director of Fish and Wildlife, said. "Their vessel can survey for 24 hours straight, she said, while local Fish and Wildlife vessels cannot.
The survey allows for investigation at depths below 50 feet and down to at least 110 feet, which is the depth near the artificial reef off Saba Island. That reef, in place for more than 10 years, originally was created from boats, concrete, metal barges and the like, and it lies entirely below a depth of 50 feet, Kojis said. The area is indicated by an "X" on the map above.
Requests to the PNR public information office more details about the target area south of St. John were not answered.
"Benthic" is a term used to describe everything that covers a portion of the ocean bottom, "inanimate as well as animate, stationary or extremely slow-moving," Ken Roger Uwate, chief of fisheries at Fish and Wildlife, said. Sonar images will show outcroppings of rock, corals, seagrass beds, algae communities (in particular, branch algae at depths around 80 feet and ball algae at depths to 110 feet, Kojis said), other habitats, and man-made deposits.
After the ultrasound images are obtained, Uwate said, "ground truthing" will be conducted in a manner similar to that done in creating topographic maps following aerial photography. Cameras dropped to the sea floor and divers will be utilized to provide more detail of specific sonar images.
Eventually, graphic results of the survey are to be posted on the Internet.
For more information on the survey project, call Uwate at 775-6762.

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