Reducing the capture of flatfish in small mesh bottom trawls using a recessed sweep 30.5 cm (12 in.) drop chain configuration
Several species of flatfish in the Southern New England (SNE) area have been assessed 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 for squid, (Loligo pealeii), butterfish (Peprilus triacanthus ) and scup (Stenotomus chrysops); these species include summer (Paralichthys dentatus), winter ( Pseudopleuronectes americanus), yellowtail (Limanda ferruginea ) and windowpane (Scophthalmus aquosus) flounders. As a result, there is a need to find gear solutions to prevent capture. A modified fishing net (MFN) was designed using a standard bottom trawl squid net with the addition of 30.5 cm (12 inch) extensions to the headrope and 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 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 12 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), flounder species (fluke, sand dabs, fourspot flounder (Paralichthys oblongus), winter flounder, yellowtail flounder) and skate (Leucoraja erinacea) which were weighed. Other appropriate bycatch was also sampled and weighed. When appropriate, flatfish species were measured and sorted into sublegal and legal sizes prior to weighing. ^ After checking 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, winter, yellowtail, fourspot and windowpane flounders. 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. ^
Agriculture, Fisheries and Aquaculture
Barbara A Somers,
"Reducing the capture of flatfish in small mesh bottom trawls using a recessed sweep 30.5 cm (12 in.) drop chain configuration"
Dissertations and Master's Theses (Campus Access).