Reducing discards in a demersal purse-seine fishery

Published source details Gonçalves J.M.S., Bentes L., Monteiro P., Coelho R., Corado M. & Erzini K. (2008) Reducing discards in a demersal purse-seine fishery. Aquatic Living Resources, 21, 135-144.
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This study is summarised as evidence for the following.

	Action	Category
	Fit escape devices (panels/grids) to encircling nets Action Link

Fit escape devices (panels/grids) to encircling nets

A replicated study in 2003–2004 of a seabed area in the Atlantic Ocean off Portugal (Gonçalves et al. 2008) found that fitting a large-diamond mesh escape panel to a bottom purse seine net reduced the amount of unwanted or undersized fish catch compared to standard nets. For seven of seven fish species, including five important discarded species (see paper for species), the average weight of the species that escaped through the large-mesh panel were 6–231 kg/set and average escape rates were 7–92% (three species >85%, four species <59%). There was no difference in average size between escaped fish and fish discarded in commercial deployments without large-mesh panels for four of seven species (with: 12.3–42.5 cm, without: 11.9–42.3 cm) but size was significantly lower for three species (with: 12.6–18.7 cm, without: 13.4–19.0 cm). Sampling was done from April 2003 to July 2004, in a 36 km stretch of water within 10 km of the south coast of Portugal, at depths from 10–33 m. Eight experimental deployments were done from a small charter vessel using a standard bottom purse seine net of 18 mm mesh fitted with a 70 mm panel of diamond mesh, 4 × 6 m in the rear wing (see paper for specifications). Fish escaping from the large-mesh panel were sampled in an 18 mm mesh cover. Catches from 61 commercial purse seine deployments were sampled separately for proportions of fish kept and discarded. For all deployments, total catches or a sub-sample if large amounts were caught were sorted by species, weighed and lengths recorded.

(Summarised by: Natasha Taylor)