Designate a Marine Protected Area and install physical barriers to prevent trawling

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

30%
Certainty

30%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

Fishing can impact subtidal benthic invertebrates through species removal or habitat damage from fishing gear entering in contact with the seabed (Collie et al. 2000). Some habitats, such as coral reefs and seagrass meadows, are particularly vulnerable to trawling gears. Specific areas can be designated as protected, and specific management measures taken to control for impactful activities (Kelleher 1999). In marine protected areas where trawling is prohibited, physical barriers, such as concrete blocks or other artificial reefs, can be placed to ensure no illegal trawling takes place, as such physical barriers would damage trawl nets (Liu et al. 2011).

When this intervention occurs outside of a protected area, evidence has been summarised under “Threat: Biological resource use – Install physical barriers to prevent illegal trawling”. Evidence for related interventions is summarised under “Habitat restoration and creation – Create artificial reefs”.

_{Collie J.S., Hall S.J., Kaiser M.J. & Poiner I.R. (2000) A quantitative analysis of fishing impacts on shelf‐sea benthos. Journal of Animal Ecology, 69, 785–798.}

_{Kelleher G. (1999) Guidelines for marine protected areas. IUCN, Gland, Switzerland and Cambridge, UK.}

_{Liu, X.S., Xu W.Z., Cheung S.G. & Shin P.K.S. (2011) Response of meiofaunal community with special reference to nematodes upon deployment of artificial reefs and cessation of bottom trawling in subtropical waters, Hong Kong. Marine Pollution Bulletin, 63, 376–384.}

Study locations

Key messages

One study examined the effects of installing physical barriers to prevent trawling in a protected area on subtidal benthic invertebrate populations. The study was in the South China Sea (Hong Kong).

COMMUNITY RESPONSE (1 STUDY)

Worm community composition (1 study): One replicated, site comparison study in the South China Sea found that sites in a protected area where physical barriers were installed to prevent trawling had a different community composition of nematode worms compared to nearby unprotected fished sites, after up to two years.
Worm species richness/diversity (1 study): One replicated, site comparison study in the South China Sea found that sites in a protected area where physical barriers were installed to prevent trawling had similar diversity and species richness of nematode worms to nearby unprotected fished sites, after up to two years.

POPULATION RESPONSE (1 STUDY)

Overall abundance (1 study): One replicated, site comparison study in the South China Sea found that sites in a protected area where physical barriers were installed to prevent trawling had fewer small invertebrates compared to nearby unprotected fished sites, after up to two years.
Worm abundance (1 study): One replicated, site comparison study in the South China Sea found that sites in a protected area where physical barriers were installed to prevent trawling had fewer nematode worms compared to nearby unprotected fished sites, after up to two years.

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

A replicated, site comparison study in 2007–2008 of four soft seabed sites in the South China Sea, Hong Kong (Liu et al. 2011) found that sites inside a marine protected area where barriers were deployed to prevent trawling had fewer small invertebrates and nematode worms, a different nematode community composition, but similar nematode diversity and species richness, compared to adjacent unprotected fished sites, after up to two years. Invertebrate abundance was lower in the protected area (198 individuals/10 cm²), compared to the unprotected fished area (290 individuals/10 cm²). Nematode abundance was lower in the protected area (183 individuals/10 cm²), compared to the unprotected fished area (280 individuals/10 cm²). Nematode community was different inside and outside the protected area (community data reported as a graphical analysis). Nematode diversity (reported as diversity indices) and species richness were typically similar in the protected (ranging from 10 to 39 species) and unprotected areas (ranging from 20 to 33 species). Increased abundances were associated with increased sediment disturbance from trawling. In 2006, a 12 km² area was designated as a marine protected area and trawling discouraged by placing artificial reefs and concrete blocks with steel spikes inside and along the boundary of the area. Two sites inside and two outside the protected area were sampled at quarterly intervals between April 2007 and January 2008 at 20 m depth using a sediment grab (0.1 m²). Small invertebrates (0.038–0.5 mm) were extracted and counted. Nematode worms were identified and counted. In the sites outside the protected area, one bottom trawl was conducted prior to each sampling.
Study and other actions tested
Referenced paper
Liu X.S., Xu W.Z., Cheung S.G. & Shin P.K.S. (2011) Response of meiofaunal community with special reference to nematodes upon deployment of artificial reefs and cessation of bottom trawling in subtropical waters, Hong Kong. Marine Pollution Bulletin, 63, 376-384.

Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K. & Sutherland, W.J. (2020) Subtidal Benthic Invertebrate Conservation. Pages 635-732 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Subtidal Benthic Invertebrate Conservation

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Establish community-based fisheries management Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Designate a Marine Protected Area and prohibit all types of fishing Action Link	Likely to be beneficial	29	Synopsis Link