Gear research to reduce bycatch in scallop dredges

Project leads: Farrell Davis and Liese Siemann

Funded by: NOAA Sea Scallop Research Set-Aside

Since CFF was founded, our researchers have conducted studies at-sea and at flume tanks to better understand fishing gear interactions and improve gear design and testing. As part of our newest efforts, we have incorporated use of cutting-edge computation fluid dynamics (CFD) simulations to speed up early testing of new gear designs. Simulations have been used to study flow patterns around a turtle-deflector dredge vs. a low-profile dredge (published in 2021). Our newest gear project takes this integrated approach one step further and couple simulation results with follow-up testing of a new gear design at sea.

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Two views of a flounder sweep tested during a 2017 gear project funded by the NOAA Bycatch Reduction Engineering Program. While flounder bycatch was significantly reduced with use of this sweep, scallop catch was also significantly reduced,

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Results from a CFD simulation of the flounder sweep show scallops being flung over the top of the dredge.

Yellowtail and windowpane flounder are both choke species for scallop operations. Abundance estimates for these flounder species are declining, and keeping commercial scallop catches of these species below the Annual Catch Limits allocated to the scallop fishery is a management priority. The goal of this project is to design a dredge modification that can be used to modify scallop dredge frames to reduce flatfish bycatch in the scallop fishery while minimally impacting scallop catch efficiency. This will be accomplished through an iterative approach of CFD testing, expert opinion, and prototype construction and testing at sea. CFD simulations will be used to test variations on two types of modifications to dredge frames: a secondary depressor plate mounted forward of and parallel to the cutting bar and simplified rubber disc sweeps. Using this multi-pronged approach saves time, effort, and, most importantly, cost compared to at-sea trials alone, allowing many more modifications to be explored at a time, and enabling more rapid optimization of scallop gear.