Evaluating the efficacy of technical measures: a case study of selection device legislation in the UK Crangon crangon (brown shrimp) fishery

Published source details Catchpole T.L., Revill A.S., Innes J. & Pascoe S. (2008) Evaluating the efficacy of technical measures: a case study of selection device legislation in the UK Crangon crangon (brown shrimp) fishery. ICES Journal of Marine Science, 65, 267-275.
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This study is summarised as evidence for the following.

	Action	Category
	Fit a funnel (such as a sievenet) or other escape devices on shrimp/prawn trawl nets Action Link
	Fit a size-sorting mesh funnel (a sieve net) to a prawn/shrimp trawl net Action Link

Fit a funnel (such as a sievenet) or other escape devices on shrimp/prawn trawl nets

A replicated, paired, controlled study in 2006–2007 in the North Sea, off the east coast of England, UK (Catchpole et al. 2008) found that trawl nets used in shrimp/prawn fisheries fitted with a sievenet (funnel-like device) appeared to catch fewer unwanted non-commercial invertebrates (discard) compared to unmodified nets. Differences were not statistically tested. Of the seven invertebrate discard species recorded, six tended to be caught in lower numbers in nets fitted with a sievenet compared to nets without (28–83% reduction in numbers caught), and one species tended to be caught in equal numbers. Use of selective gear to reduce unwanted catch in the brown shrimp fishery was made compulsory in 2003 in the European Union. Between January 2006 and January 2007, abundances of unwanted invertebrate species were compared in nets with a sievenet and without. Nets were deployed in pairs (one sievenet; one unmodified net) during 98 hauls for 1h. All organisms were identified, sorted as commercial catch or discard, and counted.

(Summarised by: Anaëlle Lemasson)
Fit a size-sorting mesh funnel (a sieve net) to a prawn/shrimp trawl net

A replicated, paired, controlled study in 2006–2007 of two inshore areas of seabed in the North Sea, England, UK (Catchpole et al. 2008) found that shrimp trawl nets fitted with a sieve net reduced the catches of unwanted fish compared to trawls without sieve nets. The average weight of unwanted fish catch was lower in trawls with sieve nets than those without (with: 6 kg, without: 11 kg). In addition, unmarketable small brown shrimp Crangon crangon and marketable shrimp catches were reduced with sieve nets by 8% and 14% respectively (with: 22–24 kg, without: 27–30 kg). Sampling was done between January 2006 and 2007 at two coastal sites from five commercial vessels fishing with twin beam trawls. Two beam trawls, were fished simultaneously; one with a sieve net and one without and data collected for 98 valid deployments. The catches from each trawl net was sorted into marketable and non-marketable sizes of shrimp and fish, counted and weighed.

(Summarised by: Natasha Taylor)