Exploring Bycatch Reduction of Summer, Winter, Yellowtail, and Windowpane Flounders Using the (12 inch) Drop Chain Trawl Net Design in the Small Mesh Fishery


Funding Organization: National Marine Fisheries Service

URI Investigators:  Kathleen Castro, Laura Skrobe, and Barbara Somers

Industry Principal Investigators: Christopher Brown, Steve Arnold and Jonathan Knight 



Several species of flatfish in the Southern New England (SNE) area have been evaluated as overfished and in need of rebuilding. These species have some common characteristics in terms of life history patterns, use of habitat, and distribution. Many are targeted species in directed fisheries; others are bycatch/discard species, especially in the small mesh fishery in SNE. These unwanted species include summer (Paralichthys dentatus), winter (Pseudopleuronectes americanus), yellowtail (Limanda ferruginea) and windowpane (Scophthalmus aquosus) flounders, as they can be potentially caught in the directed squid (Loligo pealeii), scup (Stenotomus chrysops) and butterfish (Peprilus triacanthus) small mesh fishery. As a result, there is a need to find gear solutions to avoid them. A modified fishing net (MFN) was designed using a standard bottom trawl squid net with the addition of a 30.5 cm (12 inch) drop chain between the sweep and the footrope. It was tested on its ability to reduce the capture of flatfish by creating a space between the sweep and the footrope. Initial testing to make adjustments to the sweep design of the modified fishing net was conducted at the flume tank facility at the Centre for Sustainable Aquatic Resources located at the Marine Institute of Memorial University of Newfoundland.

A bottom trawl catch characterization study was conducted aboard two commercial fishing vessels targeting squid using the “side-by-side” towing method comparing the standard fishing net (SFN) with the MFN. The nets were switched every two days and used an equal number of times on each vessel. Work was done over four months around Block Island Sound and Rhode Island Sound and consisted of 8 fishing days. Each fishing day consisted of six 40 minute tows. For each tow all

flatfish were sampled or if necessary a sub-sample was taken following Northeast Fisheries Science Center (NEFSC) protocols (NEFSC 2010). Catch included target species, (i.e. squid, butterfish, scup), unwanted flounder species (fluke, sand dabs, grey sole, winter flounder, yellowtail flounder) and skate which were measured and weighed. Other appropriate bycatch was also sampled and weighed. Flatfish were measured and sorted into sublegal and legal sizes prior to weighing and weights were taken for each fish.

After testing for vessel effects, a paired t-test was used to test for differences between the combined mean weight (catch by species) per tow in kilograms of the SFN and MFN. Results show a significant difference between mean weights per tow for summer, yellowtail and windowpane flounders. Differences between the combined mean weight (catch by species) per tow in kilograms of each potential target species (squid, scup and butterfish) were also tested using the paired t-test. There was no significant difference between mean weights captured by the SFN and MFN for all three target species.

The findings of this research indicate the 30.5 cm (12 in.) drop chain trawl net design has the ability to reduce the capture of flatfish while retaining target species in the small mesh fishery of Southern New England.