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First Wireless Monitoring System for UK Scallop Dredges

Dredgemaster is a wireless monitoring system for scallop dredges.

Notus Electronics Ltd., long time dealer in the UK, installed the Dredgemaster on the FV Vikingborg from Mallaig on the west coast of Scotland. Much of the information below resulted from the invaluable feedback from the Captain, Billy Symmonds recorded after a 3 day fishing trip. The Dredgemaster is a  wireless monitoring system for scallop dredges.  Small robust sensors are installed on the dredge. Vital dredge angle and distance information are transmitted to the vessel. 
There was a hydrophone mounted in the hull of the ship that wirelessly sent/received signals to a sensor on the dredge. A numeric display in the wheelhouse showed the pitch, wire length and scope (wire length to depth ratio). Pitch being the forward/backward angle of the dredge.
The FV Vikingborg.
After some experimenting, it quickly became evident that there is a major relationship between scope (wire length: depth) and scallop/stone catch composition. The Vikingborg normally operates down to 30Fa with wire lengths depending on water depth and swell. The only word for the seabed is "brutal:" rocks, volcanic outcrops and boulders.
Notus' Dredgemaster.
A positive angle indicates the dredge is lifting upward and a negative angle indicates the dredge is downward. With a particular scope (wire length: depth), the pitch angle increases and the towing bar lifts off the seabed. At this point, much more stones are caught.
As the scope increases, the pitch angle goes into the "sweet spot" (the angle where it catches the best), apparently catching less stones and leaving the scallops to be triggered up by the sword blades. There is a sweet spot angle for each gear configuration that appears to have a narrow pitch angle window. Increasing the scope further results in the gear angle leaving the sweet spot with a reduced scallop catch.

The Dredgemaster monitors the wire length to within 0.5 m. With the depth changing so much, wire length and speed is critical for maintaining proper dredge pitch.

About Notus
Notus Electronics Ltd. is a developer and manufacturer of advanced net monitoring solutions for the commercial fishing industry. Established since 1992, the company has brought a number of sophisticated wireless monitoring systems to the market. The overall driving force behind development and marketing has been reliable products that remain affordable for all size vessels.
Source:Notus Electronics Ltd
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Information of the company:
Address:5 Harbour Road
State/ZIP:Scotland (AB4 9TB)
Country:United Kingdom
Phone:+44 1346 512 944
Fax:+44 1346 512 535
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