Set catch limits or quotas for non-targeted commercial catch

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

Study locations

Key messages

  • Two studies examined the effects of setting catch limits or quotas for non-targeted commercial fish species on marine fish populations. One review was in the North Atlantic and Pacific Oceans and one study was in the Pacific Ocean (Canada). 





  • Reduction of unwanted catch (2 studies): One review in the Atlantic and Pacific Oceans found that setting catch limits or quotas for non-commercially targeted fish reduced unwanted catch in two of three cases. One before-and-after study in the Pacific Ocean found that catch limits for non-target commercial species reduced the amount of unwanted halibut, but a previous quota system based on the whole catch (individual transferrable quotas) did not.

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 review in 2013 of three areas (bottom and midwater) in the North Atlantic and Pacific Oceans (O'Keefe et al. 2014) reported that commercial fisheries that implemented catch limits or quota caps for non-commercially targeted fish resulted in reduced unwanted catch in two of three cases. Data were not statistically tested. Programmes that used technology to provide near real-time catch information to fishers resulted in reduced unwanted catch or discards in two of three cases compared to no use of real-time technology. Catch limits or quotas were evaluated as having reduced unwanted catch in two of three cases: of Pacific halibut Hippoglossus stenolepis in the British Columbia groundfish (bottom) trawl fishery, Canada; and in the mixed species fisheries in New Zealand. A cap for unwanted yellowtail flounder Limanda ferruginea in the USA scallop Pectinidae fishery was evaluated as having not reduced unwanted flounder catch across all affected regions even though it was successful in some areas (data not reported, see paper for references to original studies). The review summarized peer-reviewed evaluations (see paper for details of original studies) of programmes implementing unwanted catch mitigation techniques, including the setting of catch limits or quotas for unwanted or non-commercially targeted fish catch.

    Study and other actions tested
  2. A before-and-after study in 1962–2006 of bottom fishing grounds in the northwest Pacific Ocean off British Columbia, Canada (Edinger & Baek 2015) found that in the 10 years after implementing an individual vessel catch limit (quota) system for unwanted catch (“bycatch”) in a multispecies groundfish fishery, the unwanted catch of Pacific halibut Hippoglossus stenolepis (a prohibited species) was reduced, but a previous quota system limiting the amount of the whole catch (individual transferrable quotas) increased halibut catch. In the period 1996–2006 following the introduction of a “bycatch” quota system for individual vessels in 1996, halibut catches fell by 219% (data reported as statistical model results). Conversely, when individual transferrable catch quotas had been implemented in 1990, it resulted in a 40% increase in unwanted halibut catches (data reported as statistical model results). Authors noted that this increase was due to individual transferrable quotas tending to only consider the conservation of a single species rather than multiple species caught at the same time. Fisheries data from the British Columbia groundfish fishery for the period 1962–2006 were analysed, provided by The International Pacific Halibut Commission and Fisheries and Oceans Canada. The British Columbia Groundfish fishery implemented an individual vessel bycatch quota system in 1996 whereby trawl license holders received a quota representing a percentage of the species-specific total allowable catch.

    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

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Marine Fish Conservation

This Action forms part of the Action Synopsis:

Marine Fish Conservation
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