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The use of sidescan sonars, magnetometer, and video cameras in detecting illegal artificial reefs in waters of the Florida Keys
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2005
[PDF-1.50 MB]
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Alternative Title:Sidescan sonars, magnetometer, and video cameras in detecting illegal artificial reefs in waters of the Florida Keys;Detecting illegal artificial reefs in waters of the Florida Keys;
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Description:Four instruments were assessed in 2004 to determine their suitability for detecting and mapping illegally placed artificial reefs in and near the Florida Keys National Marine Sanctuary (FKNMS). The instruments were: 1) Datasonics SIS-1500 Chirp Side Scan Sonar System, 2) Geometrics G-882 Marine Magnetometer, 3) Imagenex's Sportscan Side Scan Sonar, and two locally manufactured video cameras attached to a towed body. The 42 foot RV HST-1 was deployed from Pascagoula to Key West as a platform to test the Equipment. The project was conducted from mid-June through the end of June in 2004. All instruments were towed simultaneously along five transects in a study area encompassing approximately 602 km². All transects were north of the keys between Key West and Big Pine Key. Two transects generally followed the 9.1 m (30 ft) and 12.2 m (40 ft) contours. Three transects ran from shallow water and continued perpendicular to bottom contours to a maximum depth of 14 m (46 ft). A large number of manmade structures were detected by all instruments along 4 of the 5 transects. Divers checked approximately 15 sites to verify targets. Based on the number of suspected illegal reefs detected with sidescan sonars, the estimated number of illegal reefs within the study area was 1463 (Illegal structures may number in the thousands when the study area is expanded). Given the complexity and expense of the chirper and magnetometer (along with the large number of returns from the magnetometer), they are not recommended for further use for detecting and mapping illegal artificial reefs. The smaller and less expensive Sportscan sonar, which performed nearly as well as the chirper, and the video cameras are recommended for further illegal reef studies (Scuba divers will also be required to verify some of the targets). These instruments have proven to be excellent tools for detecting illegal reefs in the addition to other underwater features such as coral heads.
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Rights Information:Public Domain
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