Evaluation of the sieve net as a selectivity-improving device in the Belgian brown shrimp (Crangon crangon) fishery

  • Published source details Polet H., Coenjaerts J. & Verschoore R. (2004) Evaluation of the sieve net as a selectivity-improving device in the Belgian brown shrimp (Crangon crangon) fishery. Fisheries Research, 69, 35-48.


This study is summarised as evidence for the following.

Action Category

Fit a size-sorting mesh funnel (a sieve net) to a prawn/shrimp trawl net

Action Link
Marine Fish Conservation
  1. Fit a size-sorting mesh funnel (a sieve net) to a prawn/shrimp trawl net

    A replicated, paired, controlled study in 2000–2001 of a seabed area in the Flemish Banks in the North Sea, Belgium (Polet et al. 2004) reported that shrimp trawls fitted with a sieve net reduced the catches of unwanted non-commercial fish compared to a standard trawl net without a sieve net. For non-commercial fish species, the average percentage reduction in catch with a sieve net compared to without was: 49% for gobies Pomatoschistus spp., 45% for dragonets Callionymus spp., 76% for seasnail Liparis liparis, 35% for pogge Agonus cataphractus, 61% for bullrout Myoxocephalus scorpius, 37% for pipefish Syngnathus spp., 61% for five-bearded rockling Ciliata mustela, 22% for pout Trisopterus luscus and 99% for anchovy Engraulis encrasicholus. In addition, the sieve net showed poor size-selectivity for all commercial fish species with lengths below 10 cm (i.e. lower escape rates), however >10 cm the selection improved with increasing length (see paper for data). Target brown shrimp Crangon crangon catches were reduced by ≤15%. Data were collected from 72 trawl deployments on a commercial fishing vessel between April 2000 and January 2001. Paired deployments (one on each side of the vessel) were done of two standard design shrimp beam trawls (20 mm codend mesh); one fitted with a 70 mm mesh sieve net (116 meshes wide at the front and 16 at the rear, 60 meshes deep) with an escape outlet in the lower trawl body ahead of the codend (see original paper for specifications). A small mesh (11 mm) cover attached over the escape opening collected catch escaping through the sieve net escape. Sub-samples of non-commercial fish catch in the cover and codend was weighed and counted.

    (Summarised by: Leo Clarke)

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