Assessing Slotted Trawl Door Efficiency using SCUBA – Year II
This project is a continuation of a 2006 grand funded project. Slotted trawl doors were designed and tested in SC waters. The aim of this study is to improve the design and rigging of these doors by using SCUBA divers making direct observations. Adjustments in rigging and modifications in design can be tried and checked for effectiveness.
There are a number of adjustments that can be made to doors and nets to increase yield and efficiency. Usually this is done by making a change on one side of the rigs and comparing the catch to the other side. A number of tows must be made to determine the effects of the changes, whether positive or negative. Having the divers look at the gear while underway will provide valuable feedback on the behavior of the gear.
One of the most important observations will be the angle of attack of the door; this is the angle of the door relative to the forward motion of the gear. It’s hoped that the angle of the louver and the flow of water across the back of the door can also be observed. It would seem that a smooth flow of water across the wing foil section would produce the best spread.