Designate a Marine Protected Area and prohibit all towed (mobile) fishing gear

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

45%
Certainty

23%
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). Mobile fishing gear such as bottom trawls, dredges, and other towed gears, are known to be particularly damaging as they are dragged onto the seabed. Specific areas can be designated as protected, and specific management measures taken to control for towed gears (Blyth et al. 2002; Sheehan et al. 2013). Inside protected areas where mobile fishing gear is prohibited, the threat from these practices to subtidal benthic invertebrates is removed, and previously impacted populations are, in theory, able to recover over time (Blyth et al. 2004). However, species and populations are still subjected to the effects of other fishing activities allowed (for instance commercial potting or recreational fishing).

When this intervention occurred outside of a protected area, evidence has been summarised under “Threat: Biological resource use - Cease or prohibit all towed (mobile) fishing gear”. Evidence for related interventions is summarised under “Habitat protection – Designate a Marine Protected Area and prohibit bottom trawling” and “Designate a Marine Protected Area and prohibit dredging”.

_{Blyth R.E., Kaiser M.J., Edwards-Jones G. & Hart P.J.B. (2004) Implications of a zoned fishery management system for marine benthic communities. Journal of Applied Ecology, 41, 951–961.}

_{Blyth R.E., Kaiser M.J., Edwards-Jones G. & Hart P.J.B. (2002) Voluntary management in an inshore fishery has conservation benefits. Environmental Conservation, 29, 493–508.}

_{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.}

_{Sheehan E.V., Cousens S.L., Nancollas S.J., Stauss C., Royle J. & Attrill M.J. (2013) Drawing lines at the sand: Evidence for functional vs. visual reef boundaries in temperate Marine Protected Areas. Marine Pollution Bulletin, 76, 194–202.}

Study locations

Key messages

Two studies examined the effects of prohibiting all towed gear in marine protected areas on subtidal benthic invertebrate populations. One study was in the Bristol Channel and the Irish Sea (UK), the other in the English Channel (UK).

COMMUNITY RESPONSE (1 STUDY)

Overall community composition (1 study): One before-and-after, site comparison study in the English Channel found that, over the three years after closing a marine protected area to all towed gears, the community composition of reef-indicative invertebrate species became different to that of unprotected fished sites.
Overall diversity/species richness (1 study): One before-and-after, site comparison study in the English Channel found that, over the three years after closing a marine protected area to all towed gears, the number of reef-indicative invertebrate species remained similar to unprotected fished sites.

POPULATION RESPONSE (2 STUDIES)

Overall abundance (1 study): One before-and-after, site comparison study in the English Channel found that, over the three years after closing a marine protected area to all towed gears, the abundance of reef-indicative invertebrate species became greater than at unprotected fished sites.
Crustacean abundance (1 study): One replicated, site comparison study in the Bristol Channel and the Irish Sea found that a marine protected area closed to all towed gear (only allowing potting) for 33 to 36 years had mixed effects on the abundances of lobsters and crabs depending on species.
Crustacean condition (1 study): One replicated, site comparison study in the Bristol Channel and the Irish Sea found that a marine protected area closed to all towed gear (only allowing potting) for 33 to 36 years had mixed effects on the sizes of lobsters and crabs depending on species.

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 summer 2004–2007 of eight sites in four areas of rocky and sandy seabed in the Bristol Channel and the Irish Sea, UK (Hoskin et al. 2011) found that a marine protected area closed to all towed gear for 33–36 years had mixed effects on the abundances and sizes of European lobster Homarus Gammarus, and three crab species. Abundances of large lobsters (≥90 mm) did not change over time in any areas, where they were similar (1–2 lobsters/line). Abundance of small lobsters (<90 mm) increased in the protected areas by 140% (due to spill-over effects from an adjacent no-take zone; from 2 to 4–7 lobsters/line), but not in the fished areas where abundance remained constant (2–4 lobsters/line). The size of large lobsters (≥90 mm) decreased similarly in all areas by 2–3% (from 98 to 95 mm). Abundance of velvet crabs Necora puber decreased inside the protected areas (from 5–6 to 1 crab/line) but increased in the fished areas (from 0–6 to 1–7 crabs/line). Abundance of brown crabs Cancer pagarus did not change over time in any areas but was on average higher in the protected areas (1–2 crabs/line) compared to the fished areas (0.3–2 crabs/line). The average size of brown crabs did not change over time in any areas, and was not different between protected (123–128 mm) and fished areas (116–130 mm). Abundance of spider crabs Maja squinado was similar in 2004 and 2007 for all areas but varied spatially. Lundy Island marine protected area was designated as a voluntary reserve in 1971 (statutory since 1986) and only allowed crab and lobster potting (all other fishing prohibited; apart from a small 4 km²no-take zone). In 2004–2007, lobsters and crabs were surveyed at two locations in the protected area (outside the no-take zone), and two unprotected fished locations (20–100 km away) (2 sites/location). Four lines of standard commercial baited shellfish pots were deployed (10 pots/line) at each site for 24 h. Upon retrieval, lobsters and crabs were counted and measured (carapace length). The pots were redeployed for five consecutive days each year.
Study and other actions tested
Referenced paper
Hoskin M.G., Coleman R.A., von C.E. & Davis C.M. (2011) Variable population responses by large decapod crustaceans to the establishment of a temperate marine no-take zone. Canadian Journal of Fisheries and Aquatic Sciences, 68, 185-200.
A before-and-after, site comparison study from 2008–2011 of 12 sites of rocky reefs and pebbly sand seabed in Lyme Bay, English Channel, southwest England, UK (Sheehan et al. 2013) found that three years after closing a marine protected area to all towed gears, community composition and abundance of reef-indicative invertebrate species became different to unprotected fished sites, but their species richness remained similar. Community data were reported as graphical analyses. Reef-indicative invertebrate species richness did not statistically change over time and was similar in closed and fished sites both before closure (closed: 8; fished: 5 species/m²) and three years after (closed: 10; fished: 5 species/m²). However, while before closure their abundance was similar in closed (6 individuals/m²) and fished sites (3 individuals/m²), it increased over time in closed sites and was greater than in fished sites after three years (closed: 16; fished: 1 individuals/m²). In particular, abundances of four key species increased in closed sites over time and became more abundant than in fished sites after three years (significantly for: bryozoans Pentapora fascialis closed 0.11 vs fished 0.01; sea squirts Phallusia mammillata 0.06 vs 0.01 and branching sponges 0.05 vs <0.01; non-significantly for hydroids 55 vs 17 individuals/m²). The 206 km² protected area was closed to towed fishing gears in 2008. Six weeks after closure (considered the ‘before’ timepoint by the authors) and in 2011, five sites inside and seven sites outside the protected area were surveyed using a video camera (two 200 m video-transects/site). All invertebrates observed on the video present on pebbly sand, but indicative of rocky reef habitat, were identified and counted.
Study and other actions tested
Referenced paper
Sheehan E.V., Cousens S.L., Stauss C., Royle J. & Attrill M.J. (2013) Drawing lines at the sand: evidence for functional vs. visual reef boundaries in temperate Marine Protected Areas. Marine Pollution Bulletin, 76, 194-202.

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

Related Actions

Actions	Effectiveness	Studies	Category
Designate a Marine Protected Area and prohibit the harvesting of sea urchins Action Link	Likely to be beneficial	2	Synopsis Link
Designate a Marine Protected Area and prohibit dredging Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Designate a Marine Protected Area and limit the density of traps Action Link	No evidence found (no assessment)	0	Synopsis Link