Effects of codend circumference and twine diameter on selection in south-eastern Australian fish trawls

  • Published source details Graham K.J., Broadhurst M.K. & Millar R.B. (2009) Effects of codend circumference and twine diameter on selection in south-eastern Australian fish trawls. Fisheries Research, 95, 341-349.


This study is summarised as evidence for the following.

Action Category

Decrease the circumference or diameter of the codend of a trawl net

Action Link
Marine Fish Conservation
  1. Decrease the circumference or diameter of the codend of a trawl net

    A replicated, paired, controlled study in 2005 of an area of seabed in the Tasman Sea, Australia (Graham et al. 2009) found that a smaller codend circumference in fish trawl nets did not reduce the discarded catch of five of five non-target fish species, or total discarded catch (fish and invertebrates). For five of five fish species (see original paper for species individual data), average catch numbers discarded were similar between small and large codend circumferences (small: 2–284 fish/haul, large: 54–502 fish/haul). The numbers (small: 753 fish/haul, large: 1,224–1,257 fish/haul) and weight (small: 104 kg/haul, large: 112–128 kg/haul) of total discarded catch (all fish and invertebrates) were also similar between codend circumferences. In addition, the number (small: 305 fish/haul, large: 685–1,468 fish/haul), but not weight (small: 94 kg/haul, large: 156–158 kg/haul) of commercial retained catch (fish and invertebrates) was lower in the smaller codend compared to the larger. Between March and November 2005, gears trials were done in a south-eastern Australian trawl fishery targeting school whiting Sillago flindersi. Three test codends, one 100 mesh and two 200 mesh circumferences, were tested in pairs during alternate deployments (16 paired deployments each) with a small mesh (40 mm) codend of 450 mesh circumference (see original paper for full specifications). Catches were counted and weighed by species and the lengths of the most abundant fish measured. Commercial species were divided into retained and discarded categories.

    (Summarised by: Khatija Alliji/Natasha Taylor)

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 21

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 ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust