Improving an Ecosystem Friendly Scallop Dredge

Dredge cutting bar comparison A) Low Profile Dredge B) Turtle Deflector Dredge C) New Bedford Dredge

Dredge cutting bar angle comparison A) Low Profile Dredge B) Turtle Deflector Dredge C) New Bedford Dredge

Project Title: Improving an Ecosystem Friendly Scallop Dredge

Year: 2015

Principle Investigators: Melissa Campbell & Farrell Davis

Client: Saltonstall Kennedy Grant Program

The Cfarm Low Profile Dredge (CFLPD) is a hydrodynamic dredge design. Increased hydrodynamic efficiency combined with low friction materials should reduce fuel consumption. The lowered height of the frame and forward cutting bar reduces the bycatch of flatfish and prevents the capture of loggerhead sea turtles (Carretta carreta) (Smolowitz et al, 2012). In addition, the prototype CFLPD has demonstrated lower impact to ecosystem component species and sharper size selectivity for scallops.

This project will further investigate ways to optimize the CFLPD to reduce bycatch. On four dedicated research trips, the CFLPD rigged with the standardized bag (8 ring apron, 2:1 twine top hanging ratio) will be compared with to the CFF control CFTDD rigged with the same standardized bag to determine the effect different scope lengths has on dredge pitch and catch for the two frame designs. This will be accomplished by completing hour long straight line tows with either a short scope (3:1) or a long scope (4:1), alternating between the short and long scope tows using an ABBA pattern. During the four paired tow cruises, control and experimental dredges will be towed simultaneously. Both dredges will be outfitted with cameras attached to the outer frame bars, facing toward the depressor plate and cutting bar to film fish behavior during the tow.