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The conch abundance indicator gives the number of queen conch (Strombus gigus) adults per unit area.This unusual shelled animal has cultural, commercial, and ecological significance in the region. It is protected to some extent by international conservation measures.

The number of adult conchs on a reef reveals a great deal about long-term prospects for the local population—which may in turn have important implications for populations in other areas. Densities lower than 50 conchs/hectare have been found to result in reproductive failure;7 recent studies indicate that the critical threshold for reproductive success may be as high as 200 conchs/ha.8

Long-term survival of this important herbivore depends on:

  • Limited fishing, including no-fishing replenishment
  • Habitat protection, especially of nursery grounds
  • Transboundary management that recognizes and
    protects the animals’ early-life dispersal phase

Because queen conch could become threatened with extinction unless its trade is strictly regulated,9 CITES10 permits, which require that stocks be stable and sustainably managed, must be issued for all exports

We recommend that queen conch be monitored through regionally standardized systematic counts and targeted process studies (for example, studies of reproduction and dispersal), inside and outside MPA11 boundaries. Assessing conch abundance is usually relatively simple and inexpensive. Collecting data on larval dispersal is more challenging but is essential for understanding the effects of management

Fully protected MPAs are an effective tool for managing conch populations. Many marine animals produce larvae that float great distances before settling down to mature, but conch larvae are thought to stay a bit closer to home during their fairly short larval phase. A network of MPAs with areas closed to conch fishing will help replenish populations throughout the region.

Site Specific Average(Region Wide) Queen Conch Density Chart

A promising sign of Benchmark reef recovery would be 50-300 conchs/ha, with narrower ranges to be eventually defined according to habitat and management zone.

  • The status of queen conch varies widely throughout
    the region. Most abundance data come from MPAs,
    which are expected to have higher densities than
    areas outside MPAs.
  • Over the past 30 years, conch populations
    and catches in many areas have been declining
    due to overexploitation, illegal harvesting of
    undersized animals, and a lack of transboundary
  • Conch numbers, which are highly responsive
    to protection measures, have made a significant
    comeback in areas where fishing has been
    limited or prohibited.12 In some no-take or highly
    restricted quota areas, numbers have rebounded
    to Benchmark or even Target levels.
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