Designate a Marine Protected Area and install physical barriers to prevent trawling
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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.
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