Prohibit certain gear types

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Two studies examined the effects of prohibiting certain gear types on marine fish populations. One study was in the Indian Ocean (Kenya) and one was in the Kattegat (Sweden/Denmark).




  • Abundance (1 study): One replicated, site comparison study in the Indian Ocean found that in an area where all but one gear type was prohibited there was a higher fish density compared to areas where just one gear type was prohibited and to unrestricted areas.



  • Reduction of unwanted catch (1 study): One replicated, before-and-after study in the Kattegat found that a combination of areas in which non-selective gear types were prohibited and long-term fishery closures reduced unwanted catch of cod compared to before.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, site comparison study in 2004 of 10 coral reef areas in the Indian Ocean off the coast of Kenya (Mangi & Roberts 2007) found that prohibiting certain gear types resulted in greater fish density in an area where all but one gear type was prohibited, compared to areas where only one gear type was prohibited, and to unrestricted sites. Fish density was higher in one area restricted to basket trap fishers only (105 fish/250 m2) compared to six areas fished by all gear types except beach seines (78 fish/250 m2) and three largely unrestricted areas (80 fish/250 m2); both sets being similar. In addition, gear regime did not affect catch levels landed by the Kenyan reef fishery (data reported as statistical results). Coral reef fishing grounds included: one location where only basket traps were allowed; six locations restricted to traditional forms of gear (traps, nets, hand lines, spears) but not beach seines; and three locations where all types of gear, including beach seines, were used. The years regulations were implemented were not reported. Fish density data were collected between January and March 2004 at 10 fishing grounds (1–125 km apart) off Kenya. Fish were identified to species and counted along four 50 × 5 m belt transects conducted at each study site during neap tides. Catch data from each fishing ground were recorded from all fish landed by individuals or groups of fishers.

    Study and other actions tested
  2. A replicated, before-and-after study in 1996–2012 of four areas of seabed in the Kattegat, off Sweden/Denmark (Vinther & Eero 2013) found that a combination of areas where non-selective gear types were prohibited and long-term fishery closures resulted in a reduction in unwanted catch (likelihood of being caught and retained) on cod Gadus morhua by the Danish bottom fleet compared to before implementation. Across all areas, fishing impact (reported as a function of fish density, fishing effort and gear size selectivity) was reduced for all size groups of cod, by 60% in the period after management measures were introduced (2009–2011) compared to the impact before (2008; see paper for data). In addition, by area, the reduction in fishing impact was largest in areas subject to permanent or partial closures, but a decline in fishing impact was also found in areas outside of closures due to a general change to more selective gears. In contrast, in a seasonally closed area, fishing impact was estimated to have increased in 2009–2010 in relation to 2008 (see paper for data). In 2009, Sweden and Denmark introduced protected areas on historically important cod spawning grounds. The protected zone had four areas in which fishing was either completely forbidden or limited to specific selective gears (Swedish size sorting grid and Danish SELTRA codend with 300 mm mesh size in exit window) throughout part, or all, of the year. Annual changes in fishing impact were estimated by overlaying the spatial and temporal distribution of cod and fishing pressure. Analyses of cod distribution were based on time-series data from six research trawl surveys (between 20–80 stations/year spanning 1996–2012) in the first, third and fourth quarters of a year. Fishing effort data from the Danish fleet in the Kattegat derived from logbooks and satellite-based vessel monitoring systems were analysed for the period 2008–2011.

    Study and other actions tested
Please cite as:

Taylor, N., Clarke, L.J., Alliji, K., Barrett, C., McIntyre, R., Smith, R.K., and Sutherland, W.J. (2021) Marine Fish Conservation: Global Evidence for the Effects of Selected Interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Marine Fish Conservation

This Action forms part of the Action Synopsis:

Marine Fish Conservation
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