Designate a Marine Protected Area and prohibit the harvesting of conch

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

Effectiveness

50%
Certainty

22%
Harms

12%

Calculating overall effectiveness category

Background information and definitions

Conch populations have significantly declined due to overharvesting for commercial and recreational purposes (Theile 2001). Specific areas can be designated as protected, and specific management measures taken to cease or prohibit the harvest of conch (Béné & Tewfik 2003; Stoner et al. 2012). Inside protected areas where this activity is prohibited, the threat from conch harvesting to conch populations and associated benthic communities is removed, and previously impacted populations are, in theory, able to recover over time (Stoner et al. 2012). When this intervention occurred outside of a marine protected area, evidence for the effects on conch populations is summarised under “Species management – Cease or prohibit the harvest of conch”. Evidence for related interventions is summarised under “Threat: Biological resource use”.

_{Béné C. & Tewfik A. (2003) Biological evaluation of marine protected area: evidence of crowding effect on a protected population of queen conch in the Caribbean. Marine Ecology, 24, 45–58.}

_{Stoner A.W., Davis M.H. & Booker C.J. (2012) Negative consequences of Allee effect are compounded by fishing pressure: comparison of queen conch reproduction in fishing grounds and a marine protected area. Bulletin of Marine Science, 88, 89–104.}

_{Theile S. (2001) Queen conch fisheries and their management in the Caribbean. Brussels: TRAFFIC Europe.}

Study locations

Key messages

One study examined the effects of prohibiting the harvesting of conch in marine protected areas on their populations and/or other subtidal benthic invertebrates. The study was in the North Atlantic Ocean (British Overseas Territories).

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Mollusc abundance (1 study): One site comparison study in the North Atlantic Ocean found that a marine protected area prohibiting the commercial harvest of conch had more conch after five years compared to a fished area.
Mollusc condition (1 study): One site comparison study in the North Atlantic Ocean found that a marine protected area prohibiting the commercial harvest of conch had smaller adult conch after five years compared to a fished area.

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 site comparison study in 1998 in areas of algal seabed, sandy seabed, or seagrass bed in the North Atlantic Ocean, Turks and Caicos Islands, British Overseas Territories (Béné & Tewfik 2003) found that inside a marine protected area that had been prohibiting the commercial harvest of conch for five years, abundance of queen conch Strombus gigas was higher compared to a fished area, but effects varied with the age of conch and habitat type. Total conch abundance (juveniles and adults) was higher in the closed (555 conch/ha) compared to the fished area (277 conch/ha). Abundance of adult conch (≥4 mm lip thickness) was higher in the closed compared to the fished area for algal habitat (closed: 833 vs fished: 86) and sandy habitat (78 vs 28), but not statistically different for seagrass habitat (410 vs 24). Abundance of juvenile conch (<4 mm lip thickness) was similar inside and outside the closed area for all habitats (179–483 vs 85–497). In addition, adult conch were smaller in the closed area compared to the fished area (186 vs 204 mm shell length). In 1993 a conch sanctuary (approximately 17.5 km²) prohibiting the commercial harvest of conch was experimentally established. In June–November 1998 at an unspecified number of sites both inside and outside the sanctuary, divers counted and measured (shell length and lip thickness) all conch in 6 x 60 m transects at 0.2–12 m depth.
Study and other actions tested
Referenced paper
Béné C. & Tewfik A. (2003) Biological evaluation of marine protected area: evidence of crowding effect on a protected population of queen conch in the Caribbean. Marine Ecology, 24, 45-58.

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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Designate a Marine Protected Area and prohibit all types of fishing Action Link	Likely to be beneficial	29	Synopsis Link
Designate a Marine Protected Area and prohibit bottom trawling Action Link	Unknown effectiveness (limited evidence)	3	Synopsis Link