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Providing evidence to improve practice

Action: Cease or prohibit commercial fishing Subtidal Benthic Invertebrate Conservation

Key messages

Read our guidance on Key messages before continuing

  • Three studies examined the effects of ceasing or prohibiting commercial fishing on subtidal benthic invertebrate populations. Two studies were in the Tasman Sea (New Zealand), the third on Gorges Bank in the North Atlantic Ocean (USA).



  • Overall community composition (1 study): One site comparison study in the Tasman Sea  found that an area closed to commercial trawling and dredging for 28 years had different overall invertebrate communities than an area subject to commercial fishing.
  • Overall species richness/diversity (1 study): One site comparison study on Georges Bank found no difference in invertebrate species richness between an area closed to commercial fishing for 10 to 14 years and a fished area.


  • Overall abundance (2 studies): Two site comparison studies in the Tasman Sea  and on Georges Bank found that areas prohibiting commercial fishing for 10 to 14 years and 28 years had greater overall invertebrate abundance compared to areas where commercial fishing occurred. One of the studies  also found higher biomass, while the other found similar biomass in closed and fished areas.
  • Crustacean abundance (1 study): One replicated, site comparison study in the Tasman Sea found that in commercial fishing exclusion zones lobster abundance was not different to adjacent fished areas after up to two years.


  • Overall community biological production (1 study): One site comparison study in the Tasman Sea  found that an area closed to commercial trawling and dredging for 28 years had greater biological production from invertebrates than an area where commercial fishing occurred.

Supporting evidence from individual studies


A replicated, site comparison study in 2006–2007 of 12 rocky seabed sites in the Tasman Sea, Fiordland, New Zealand (Jack & Wing 2010) found that a zone excluding commercial fishing did not have a higher abundance of red rock lobster Jasus edwardsii compared to adjacent fished areas, after up to two years. Lobster abundance was similar in the exclusion zone (2 individuals/250 m2) and the fished areas (1 individual/250 m2). In 2006 and 2007, divers surveyed eight sites within a commercial fishing exclusion zone set in 2005, and four fished sites (at 15 m depth). Red rock lobsters were counted along 50 x 5 m transects (1 transect/site in 2006, 3/site in 2007).


A site comparison study in 2004–2008 in two areas of gravelly and sandy seabed on Georges Bank, northwest Atlantic Ocean, USA (Smith et al. 2013) found that an area closed to certain commercial fishing had a higher biomass of invertebrates attached to the seabed (epifaunal), but not a higher total abundance or species richness, compared to a fished area, 10–14 years after closure. Epifaunal biomass was significantly higher in the closed area (33–109 g/L) compared to the fished area (26–57 g/L). Total epifauna abundance was similar in closed (6–15 individuals/L) and fished areas (6–10 individuals/L). The effect of closing commercial fishing on species richness varied with years, but overall across year species richness was similar in both areas (closed: 26–39; fished: 32–41 species). An area on Georges Bank was closed to all commercial fishing gear capable of retaining ground fish (trawls, scallop dredges, gill nets and hook gear) in December 1994. Annually in 2004–2008, one site in the closed area and one site in an adjacent fished area were surveyed at 45–55 m depth. Epifauna were collected using a dredge (2–3 samples/site/year; 6.4 mm mesh liner), identified, counted, and wet-weighed.


A site comparison study in spring 2008 of 48 sites in a soft seabed area in the Tasman Sea, New Zealand (Handley et al. 2014) found that sites within an area closed to commercial trawling and dredging for 28 years had different invertebrate communities, and higher invertebrate abundance, biomass and productivity than sites subject to intense fishing. Community data were presented as graphical analyses. Sites closed to fishing had greater invertebrate abundance (particularly large and small sizes, but not medium-size), and higher biomass and biological productivity, compared to fished sites (data presented as effect sizes). The larger, rarer individuals contributed the most to the biomass and productivity estimates within the closed sites. Separation Point exclusion zone was legally closed to commercial fishing and shellfish dredging in 1980. In 2008, sediments were collected from the western and southern edges of the exclusion zone, each with 12 samples on each side (24 samples inside and 24 outside the closed area in total) using a grab (0.07 m2) at 20–30 m depth. Invertebrates (>0.5 mm) were extracted, identified and counted. Biomass and productivity were estimated using size-based conversion factors.

Referenced papers

Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K., and Sutherland, W.J. (2019) Subtidal Benthic Invertebrate Conservation: Global Evidence for the Effects of Interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.