Investigating the Impacts of Speed on Dredge Performance


The Dillon QuickCheck RED tension system used to determine tow resistance of the dredge frame

Project Title: Determination of the Impacts of Dredge Speed on Bycatch Reduction and Scallop Selectivity

Year: 2015

Principle Investigators: Farrell Davis, Chris Parkins, & Melissa Campbell

Client: NOAA/NMFS Atlantic Sea Scallop Research Set-Aside Program

The Coonamessett Farm Turtle Deflector Dredge (CFTDD) has proven to be successful in reducing the bycatch of loggerhead sea turtles (Carretta carreta) without a significant reduction in scallop catch. Different bag designs tested in combination with the CFTDD frame have been effective at reducing finfish bycatch as well. However, some fishermen have reported that the CFTDD is less fuel efficient and that it “fishes” better at higher speeds (5.5 knots compared to the traditional 4.5 knots). Towing at higher speeds can potentially have significant impacts on catch per unit effort (CPUE), scallop size selectivity, and fish bycatch rates.

The purpose of this project is to continue testing this gear that reduces bycatch with a focus on the impact of dredge towing speed. Furthermore the energy efficiency of towing the frame at the different speeds will be tested to determine the economic impact of design changes. Research will compare a standardized CFTDD rigged with the standardized bag (8 ring apron; 2:1 twine top hanging ratio) with to a CFTDD rigged with an experimental bag (5R apron; 1.5:1 twine top hanging ratio) at an average of 4.0 knots and 5.5 knots. The project will consist of four  7 day research trips employing various limited access commercial scalloping vessels to conduct speed trials on Georges Bank and southern New England. Tows will be conducted in areas of high yellowtail and winter flounder bycatch and a wide range in scallop size to better examine changes in scallop size selectivity due to speed.