Cease or prohibit all commercial fishing

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

Study locations

Key messages


  • Community composition (3 studies): Two before-and-after studies (one site comparison) in the Tasman Sea and South China Sea found that the fish assemblage/species composition was different before and after prohibiting all commercial fishing, in an estuary after two years, and in the nearby wider region surrounding two marine reserves five years after their creation. One site comparison study in the South Atlantic Ocean found no change in species composition between a reserve closed to all commercial fishing for 40 years and unprotected fished areas.
  • Richness/diversity (2 studies): One site comparison study in the South Atlantic Ocean found no difference in overall fish diversity between a protected area closed to all commercial fishing for 40 years compared to unprotected fished areas. One before-and-after study in the South China Sea found that fish species richness decreased in the wider region five years after all commercial fishing was banned in two marine reserves.


  • Abundance (7 studies): Two of four site comparison studies (one replicated, one before-and-after) in the Mediterranean Sea, Indian Ocean, south Atlantic Ocean and the Gulf of Mexico found that in protected areas prohibiting all commercial fishing for five years and 40 years there were higher abundances of three of 12 commercially targeted and non-targeted fish species/groups and one of four commercially targeted fish species, compared to unprotected fished areas. One study found mixed effects on fish densities 30–40 years after banning all commercial fishing, varying with level of commercial exploitation, and higher abundances of five of five commercially exploited species. The other study found there was no increase in white seabream and gilthead bream biomass 2–13 years after closure compared to an unprotected fished area, but it was lower than a no-take area protected for over nine years. One before-and-after, site comparison study in the Tasman Sea found that most fish species in an estuary in a marine reserve had a lower abundance two years after it was closed to all commercial fishing than before, as did one of two reference sites in unprotected adjacent estuaries. One before-and-after study in the South China Sea found that in the five years after the creation of two marine reserves with limits on commercial fishing activity, overall fish density in the nearby wider region increased. One replicated, site comparison study in the Tasman Sea found that in areas of a marine reserve closed to commercial trapping, fish abundance varied over 10 years and was higher for some groups than others compared to reserve sites open to trapping.
  • Condition (1 study): One replicated, site comparison study in the Indian Ocean found that in marine reserve areas banning all commercial fishing for five years, overall fish size was bigger compared to fished areas.


  • Use (1 study): One replicated, controlled study in the Greenland Sea found that areas closed to commercial fishing (trawling) had higher recaptures of tagged smaller immature cod than adult cod over time compared to trawled areas, indicating they were more likely to have an increased protection from fishing.

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 site comparison study in 1992–2005 of three rocky areas in the northwest Mediterranean Sea off the coast of Spain (Rius & Zabala 2008) found that two to 13 years after commercial fishing was prohibited in a partially fished zone of a marine reserve, there was no increase in the biomass of white seabream Diplodus sargus and gilthead bream Sparus aurata compared to an unprotected fished area. Across all years, the average biomasses of white and gilthead bream were similar between partially fished (white: 5.9 g/m2, gilthead: 0.1 g/m2) and fished areas (white: 6.1 g/m2, gilthead: 0.2 g/m2). However, both were lower compared to a no-take zone of the reserve, unfished for over nine years (white: 19.1 g/m2, gilthead: 0.8 g/m2). Fish were sampled annually from 1992–2005 at three nearby sites, up to 2 km apart: a partial reserve (angling permitted only, no collection of subtidal animals since 1990); a fished stretch of coastline; and a no-take reserve in the Medes Islands Marine Protected area (no extractive activities, since 1983). Numbers of fish at each site were recorded by underwater visual transects (no further sampling details were provided).

    Study and other actions tested
  2. A before-and-after, site comparison study in 2001–2005 of a mangrove and saltmarsh estuary in the Tasman Sea, New South Wales, Australia (Saintilan et al. 2008) found that two years following closure to commercial fishing, there was a different fish assemblage and lower abundance of most species compared to before the closure, and a similar change was found at one of two reference sites in adjacent estuaries. The fish assemblage at the estuary closed to commercial fishing differed before and after closure and overall abundances (mangrove and saltmarsh habitats combined) of only two of the 12 main fish species increased, while the rest decreased (data reported as statistical results - see original paper). The fish assemblage at one of two reference sites in similar nearby estuaries also differed following the closure and no change was observed at the other (data reported as statistical results). The authors suggested that the reported decline in abundance may have been due to an increase in predation by larger fish after the closure. Botany Bay was closed to commercial fishing (netting and trapping) in mid-2002. Fish were surveyed at the Towra Point Nature Reserve in Botany Bay and two nearby reference sites (no details of fishing activity were reported), in June-August and December-February immediately prior to (2001–2002) and two years after (2004–2005) the closure. Fish were sampled using 4 m fyke nets set at 50 m intervals: four replicate deployments in saltmarsh habitat and two in mangroves/site before the closure, increased to three deployments in mangroves after.

    Study and other actions tested
  3. A replicated, controlled study in 1994–1995 of five areas of seabed in the Greenland Sea, off northwest Iceland (Schopka et al. 2010) reported that prohibiting all or some commercial fishing in marine protected areas and other areas closed to trawling, provided more protection from fishing for immature cod Gadus morhua, whose movement patterns indicate they are relatively stationary, but not for the migratory adults. The spatial distribution of recaptured cod over time was similar for all sites and tagging years, and there were no differences between cod tagged inside protected areas compared to outside (data reported graphically). However, there were clear seasonal and size-based differences over time, and the proportion of small cod recaptured at sizes <55 cm was lower for the area with the highest level of protection from fishing (4–9%) than most of the fished areas (7%, 21% and 25%), and the other marine protected area (15%). In addition, for small cod but not large cod, distance from areas of higher fishing intensity may also have influenced recapture patterns. Tagging surveys took place within five areas in July 1994 and June 1995 using two types of conventional tags. A total of 5,173 small cod (40–54 cm) were tagged in five areas: a marine protected area closed permanently to commercial fishing since 1993 (1,687 cod); a protected area closed to otter trawling and longlining since 1993, but open to a seasonal fishery (Oct-Mar) since 1997 (572 cod); two nearby inshore areas closed to trawling (1,916 cod); and one nearby area with no fishing restrictions (998 cod). Data on cod recaptures were analysed from a subset (224, anchor tags only) of the 719 (14%) tag returns made by fishers to the Marine Research Institute from 1994–2000. Most recaptured fish (78–94%, depending on tagging area) were caught in the first 3 years after tagging.

    Study and other actions tested
  4. A replicated, site comparison study in 2005 of five coral reef sites in the Indian Ocean, off the coasts of South Africa and Mozambique (Currie et al. 2012) found that five years after prohibiting commercial fishing in partially protected areas of two marine reserves, there was an increased abundance of three of 12 commercially targeted and non-targeted fish species/groups, compared to unprotected fished areas, and overall, fish were larger. Average abundance was higher in the partially fished areas than openly fished areas for groupers Epinephelinae spp. (0.7 vs 0.3 fish/count), yellow-edged lyretail Variola louti (0.3 vs 0.1 fish/count) and butterflyfish Chaetodontidae (3.2 vs 2.6 fish/count). Similar abundances between areas were recorded for snappers Lutjanus spp. (0.3 vs 0.5 fish/count), two-spot red snapper Lutjanus bohar (0.1 vs 0.0 fish/count), emperorfish Lethrinidae (0.1 vs 0.0 fish/count), surgeonfish Acanthuridae (6.2 vs 10.0), goldbar wrasse Thalassoma hebraicum (2.3 vs 1.9 ), grunts Plectorhinchus spp. (0.1 vs 0.2) and parrotfish Scaridae (1.1 vs 1.3). In partially fished areas abundances were lower than in openly fished areas for green jobfish Aprion viriscens (0.0 vs 0.3 fish/count) and jacks Caranx/Carangoides spp. (0.3 vs 2.1 fish/count). Average fish size (reported a standardised measure) was higher in partly fished (58) than openly fished areas (48). In April 2005, fish were sampled at four partly protected areas (limited non-commercial/non-trawl fishing types and diving permitted, next to no-take reserve areas) of two adjacent marine reserves (designated 1999), and at five openly fished sites outside the reserves (two adjacent and three >200 km away). At each site, divers counted selected fish species >7 cm in length, along two replicates of bisecting transect pairs 25 m long and 5m wide. Point counts (22–32) were also conducted at each site in a 5 m radius, separated by 20 m. Data were analysed for seven coral-dominated sites (three part protected and two open).

    Study and other actions tested
  5. A before-and-after, site comparison study in 1999–2011 of a large managed reef area in the Gulf of Mexico, Florida, USA (5) found that fish densities in an area of a marine reserve where commercial fishing had been prohibited for over 30 years, varied with level of commercial exploitation over a ten-year period and immediately following conversion of half of the area to no-take (no fishing), and abundances of five of five commercially exploited species were greater compared to adjacent openly fished areas. For five of five commercially targeted fish, increases in density were detected in 2–7 surveys (out of 7) in the non-commercially fished area and there were no decreases, while in the fished areas an increase in density was detected in one of four surveys and density decreased in two to three. For 11 non-target fish species, five species collected for the aquaria trade and two protected groupers Epinephelus spp., changes in density fluctuated between years in both areas (see paper for species individual data). In addition, adult percentage abundances of the five commercial species increased overall in the non-commercially fished area from baseline levels (1999–2000) of 49–71% to 54–87% in 2008–2010 (a year after half of the area was made no-take), while abundances in openly fished areas showed overall decreases (1999–2000: 9–27%, 2008–2010: 1–23%). Fish were monitored in two areas of the Dry Tortugas region with different levels of management protection: Dry Tortugas National Park (~320 km2, fishing prohibited except hook and line angling since the 1960s; half of the area designated as no-take in 2007) and an area with open access to commercial and recreational fishing. Both areas were adjacent to other no-take reserves. Baseline fish surveys were done in 1999–2000 (two surveys) and monitoring surveys every one or two years from 2002–2011 (seven surveys in non-commercially fished and four in fished areas). A total of 8,106 diver visual counts were done in a two-stage stratified random sampling design. Numbers of reef fish were recorded in randomly selected circular plots 15 m in diameter.

    Study and other actions tested
  6. A before-and-after study in 1994–2005 of a large area of soft, shelly mud seabed in the South China Sea, Hong Kong, China (Tam et al. 2013) found that after prohibiting commercial fishing in two protected marine reserves as mitigation for a large-scale land reclamation project, fish species composition in the wider region changed, overall fish density increased but species richness decreased, in the five years after implementation. Fish species composition changed in the period after both reserves were established (2001–2005) compared to before (1994–1999) (data reported as graphical analysis). Fish densities in the region were higher overall after both reserves were established than before (after: 97,000–280,000 fish/km2, before: 11,000–12,000 fish/km2), but peaked in 2003 before declining in 2004 and 2005. Over the same period, fish species richness decreased (after: 84–103, before: 127–140 species). Between December 1992 and early 1996, a huge coastal development to reclaim 9.4 km2 of land from the sea north of Lantau Island was completed in the study area. To reduce impacts on dolphin habitats, two nearby and adjacent marine reserves (12 km2 and 460 km2) were created in December 1996 and October 1999 respectively, zones of which prohibited commercial fishing and other human activities. Fish were sampled at 1–6 sites/survey in an area up to 10 km from the reclaimed land by beam trawl (total 882 deployments), annually from 1994–1995 and 1999–2005. Catch data from sampling sites, including one in the smaller of the reserves, were pooled for each year.

    Study and other actions tested
  7. A site comparison study of an area of reef, sand and kelp in the South Atlantic Ocean, off the coast of South Africa (Roberson et al. 2015) found that prohibiting commercial fishing in a marine protected area for 40 years increased the abundance of one of four commercially targeted fish species compared to unprotected fished areas outside, but did not increase overall fish diversity or change species composition. Average abundance was higher inside the non-commercially fished area than outside for hottentot Pachymetopon blochii (inside: 5.0, outside: 2.6 max. number) and was similar between areas for roman seabream Chrysoblephus laticeps (1.3 vs 0.9 max. number), panga seabream Pterogymnus laniarus (6.7 vs 4.3 max. number) and carpenter seabream Argyrozona argyrozona (1.6 vs 1.1 max. number). Numbers of species, diversity (Shannon-Wiener values) and overall fish species composition were similar inside (no. species: 34, Shannon-Wiener: 1.73) and outside (no. species: 39, Shannon-Wiener: 1.43) the non-commercially fished area. Fish were surveyed inside and outside the Betty’s Bay Marine Protected Area (20 km2, commercial fishing prohibited but recreational fishing allowed since 1973). Four steel baited remote underwater video cameras were simultaneously deployed for one hour at 30 stations within and 28 stations in adjacent areas outside the protected area. For each video camera, all fish species and the maximum number of any species in a single frame 35 cm off the seabed and centred on a bait canister 1 m away were recorded. The earliest the survey took place was in 2012 but no details of sampling times were provided.

    Study and other actions tested
  8. A replicated, site comparison study in 2002–2012 of eight rocky coral reef sites in the Tasman Sea, New South Wales, Australia (Malcolm et al. 2016) found that in areas of a marine park where commercial trapping was prohibited, there was a higher abundance of some fish species or groups over a 10 year period following implementation, compared to park areas open to commercial trapping. Abundances varied between years, but overall average abundances of two of 10 targeted fish species/groups and one of two non-targeted groups were higher at non-commercially fished areas than commercially fished areas, one targeted species was lower and the rest were similar between areas (data reported as statistical results and presented graphically for some species only). Fish assemblages were monitored annually in 2002–2007, 2009 and 2012, at eight sites, in the Solitary Islands Marine Park: two sites in each of two management areas where recreational fishing but no commercial fish trapping was permitted (>200 ha); and four sites in areas where commercial trapping and recreational fishing were permitted. The park was originally designated in 1991 and rezoned in 2002. At each site, fish were surveyed by six underwater visual transects (125 m2) and three replicate five-minute timed-swim counts (250 m2).

    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?

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Marine Fish Conservation

This Action forms part of the Action Synopsis:

Marine Fish Conservation
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