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2003 ROV Pilot Project

Underwater Gear Groundline Profile Work

Project Goals:

  1. To assess the equipment, techniques and procedures that will be used in an upcoming study of lobster gear and to document experimental modifications designed to reduce entanglement potential for marine mammals.  

  2. To provide background information on the underwater profile of sink, float and neutrally buoyant rope.

  3. To stimulate interest among industry members in both gear modification ideas and the ROV project itself.

Materials and Methods 

Using a remote operated vehicle (ROV model type: Benthos MK MiniRover System), the groundline profiles of various rope and trap configurations were filmed in three locations along the Maine coast during February and April 2003.  Observers recorded the type and lengths of rope used for the groundline and gangion/ bridle as well as the depth of the set, tide and bottom type (either hard or mud).  The ROV provided a visual image of how the rope behaved after the traps were set, as well as the relative height of the ropes from the seafloor.  This information was recorded for each set.  Three locations were filmed (Casco Bay, Cutler, and Southwest Harbor) and sets ranged from 7- 25 fathoms.  Except for in Southwest Harbor, where preliminary modification ideas were also tested, all gear was tested as it is actually used. 

Summary Results   

A large number of variables affect ground line profile, such as speed of set, tide speed and direction, depth of water, whether the set direction is with or against the tide, and how the traps leave the boat.  Initial observations from the ROV footage imply the behavior of sink rope to be as intended, lying on or slightly above the seafloor.  Neutrally buoyant rope was observed to behave in a similar manner to sink rope.  Float rope was often observed to be 7 or 8 feet from the seafloor.  This study generated operational information necessary for the formulation of our approach to future ROV work.  Specific challenges included manipulating the ROV around end lines, finding gear in water greater than 20 fathoms deep, and retrieving the ROV during strong tides in the Cutler area.  More than ten hours of ROV footage and four hours of topside video were recorded.  Nine industry members participated directly in the study, and many others were involved with the project.  From the raw footage, two 15- 20 minute videos were produced.  These videos were mailed to project participants and shown at the Maine Fishermen’s Forum (Feb 28) and the Atlantic Large Whale Take Reduction Team meeting (April 29).  Many viewers reported surprise at the high vertical profile of float rope and expressed interest in experimenting with gear modifications of their own.  Overall, the project was successful and contributed  important background information for the experimental design of future gear studies.

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