Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device

Published source details He P. & Balzano V. (2007) Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device. ICES Journal of Marine Science, 64, 1551-1557.
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This study is summarised as evidence for the following.

	Action	Category
	Use a different design or configuration of size-sorting escape grid/system in trawl fishing gear (bottom and mid-water) Action Link

Use a different design or configuration of size-sorting escape grid/system in trawl fishing gear (bottom and mid-water)

A replicated, paired, controlled study in 2006 of a bottom fishery in the Gulf of Maine, Atlantic Ocean, USA (He & Balzano 2007) found that using a different configuration of size-sorting escape grid (two grids) in a shrimp trawl net did not typically reduce the capture of unwanted fish compared to a conventional net with just one grid. In two of two trials (with and without guiding funnels), average catch rates of four of five unwanted fish species (whiting Merluccius bilinearis, long rough dab Hippoglossoides platessoides, redfish Sebastes spp., and red hake Urophycis chuss) were similar between two-grid and single grid nets (two: 4–120 fish/h, single: 5–129 fish/h). For the other species, witch flounder (Glyptocephalus cynoglossus, catch rate was similar between grid nets when no guiding funnel was used (two: 20 fish/h, single: 21 fish/h), but lower in the two-grid system when it was used (two: 27 fish/h, single: 51 fish/h). In addition, average size of the target commercial species Northern shrimp Pandalus borealis was larger for both designs of the two-grid nets compared with the single grid (two: 21.4–21.8 mm, single: 20.0–21.2 mm). Between March and June 2006, data were collected from 11 (two grid/no funnel) and 14 (two grid/with funnel) paired deployments by inshore trawlers of nets fitted with secondary grid systems and standard nets with one grid alone. Two-grid nets were fitted with a standard grid design (Nordmøre, 25 mm bar spacing, top opening for fish escape), plus a smaller shrimp size-sorting grid (11 mm bar spacing, bottom opening to allow small shrimp escape), and either a guiding funnel or no funnel. Control nets were fitted with a Nordmøre grid alone and a funnel (see original paper for specifications). Numbers, weights and sizes of individuals of the main non-target fish species and the target shrimp species were recorded.

(Summarised by: Natasha Taylor)