Other ID: none
Organization(s): USGS, Woods Hole Coastal and Marine Science Center
Principal Investigator(s): Bradford Butman
Data Type(s): Time Series: Mooring (physical oceanography)
Scientific Purpose/Goals: The objective of this short cruise was to attempt to locate and recover a current mooring deployed at 34 54.7 N, 120 59.5 W in about 400 m of water off Pt. Sal, CA. The mooring, containing 3 EG&G vector averaging current meters, was deployed as part of the California Monitoring Program (CAMP) in May 1987 and was to be recovered in July 1987. No attempt could be made to recover or interrogate the mooring on the July cruise because of heavy weather and ship failures. Recovery was re-scheduled for September. On this cruise, the mooring did not respond to any acoustic commands; it was assumed that either the release had failed or that the mooring was dragged away by fishing activity. Because of the equipment and importance of the data, an additional acoustic search using the release gear, a sidescan sonar search with an EG&G 50 kHz system, and a search utilizing a remotely operated vehicle (ROV) were planned to attempt to locate the lost mooring.
Start Date: 1987-11-01
Start Port/Location: Ventura, CA
End Date: 1987-11-03
End Port/Location: Port San Luis, CA
Equipment Used: Bottom tripod
Information to be Derived:
Summary of Activity and Data Gathered: The mooring was not located using any of the search techniques. The acoustic search for the release was conducted over an area approximately 5 nmi north, south, east and west of the original deployment site. The sidescan search was conducted along lines about 4 mi long (2 mi either side of the mooring site) running approximately NW-SE and spaced 100 m apart. The length of the lines was dictated by the distance necessary for the sidescan fish to straighten out following turns. The sidescan was set on a 100 m range so the line coverage overlapped about 50%. In the time allotted for this search, 7 sidescan lines were run. Coverage extended about 560 m in the along-isobath and cross-isobath directions in the immediate vicinity of the mooring. All navigation during the sidescan survey was conducted using the Land and Sea system; the ship position on the desired track was excellent throughout the survey. No obvious sidescan target was located. However, extensive trawl marks were observed throughout the region, especially at the depth range of the mooring. Most trawl marks were along-isobath, but many also were oblique to the isobaths. If moved by trawlers, the mooring could be in any direction from the original site. At the very end of the cruise, the seas had calmed sufficiently to enable a brief search with the ROV. A sonar search (100 m radius) at about 375 m depth at the mooring site and 100 m to the north of the mooring site indicated no target. No more time was available for further search or for investigation of the sea floor. Based on this search, it is concluded that the mooring is lost and that the most probable cause of loss is an encounter with fishing activity.
Staff: Bradford Butman, William J. Strahle
Notes: Original Center People field contained: Brad Butman - Ch. Sci.; Bill Strahle - Electrical Engineer; Mike Boyle - Sidescan Technician.
Point Sal, California, United States, North America, North Pacific;