Designate a Marine Protected Area and prohibit the harvesting of conch
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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.
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