Study

Diamond vs. square mesh codend in a multi-species trawl fishery of the western Mediterranean: effects on catch composition, yield, size selectivity and discards

  • Published source details Ordines F., Massutí E., Guijarro B. & Mas R. (2006) Diamond vs. square mesh codend in a multi-species trawl fishery of the western Mediterranean: effects on catch composition, yield, size selectivity and discards. Aquatic Living Resources, 19, 329-338.

Actions

This study is summarised as evidence for the following.

Action Category

Use a square mesh instead of a diamond mesh codend in a trawl net

Action Link
Marine Fish Conservation
  1. Use a square mesh instead of a diamond mesh codend in a trawl net

    A replicated, controlled study in 2002–2003 in two areas of seabed on the continental shelf in the Mediterranean Sea, Spain (Ordines et al. 2006, same experimental set-up as Guijarro & Massuti 2006) found that using a square mesh instead of diamond mesh codend in a multi-species bottom trawl fishery reduced the amount of fish discarded in deeper but not shallower shelf areas, and size-selectivity was improved in both areas. Average catch biomass of total discarded fish (80–90% of which were non-commercial species) was lower in the square mesh codend on the deep shelf (square: 10, diamond: 20 kg/30 min) and similar between mesh shapes on the shallow shelf (square: 6, diamond: 10 kg/30 min). The length at which 50% of fish are predicted to escape, where reported, was higher in the square mesh in both shallow and deep areas for all fish (square: 7–29 cm, diamond: 2–19 cm; see paper for species individual data). Fishing deployments were conducted from a commercial trawler in September–October 2002 and May–June 2003 (same experimental set-up as Guijarro & Massuti, 2006), on the shallow (50–78 m, 12 hauls) and deep (147–189 m, 12 hauls) continental shelf off the Balearic Islands. Twelve hauls were carried out in each area: 6 each of a square and diamond mesh codend (both 40 mm mesh size). A small mesh (20 mm) cover installed over the codends sampled catch escaping through the meshes.

    (Summarised by: Chris Barrett)

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 18

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust