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Ragged Island and Jumento Cays 2013

Objective

The primary objective of the Jumentos Cays and Ragged Islands was to survey the density, abundance and population structure of queen conch stocks in the shallow commercial fishing grounds between Water Cay in the north and Little Ragged Island at the southern extreme of the island chain.

Findings

  • Average density of flared-lip queen conch (“adults”) over the Jumentos Cays and Ragged Islands was 122 “adults”/ha) (no. per hectare = no./10,000 m2).
  • Density values decreased generally from north to south in the island chain, ranging from a high of 168 “adults”/ha near Flamingo Cay to just 10/ha in the southern sector encompassing Raccoon Cay to Little Ragged Island.
  • Densities of three year old conch (here called “subadults” or “rollers”) were relatively low, with an average value of 14.8/ha in the island chain.
  • The numbers of mating pairs observed in 176 survey lines throughout the study area revealed that most mating occurred at “adult” densities > 85/ha. This corresponds closely with other lightly fished areas in The Bahamas and supports the recommendation of conch experts that fishery management for the species should be designed to achieve minimum densities of 100 adults/ha.
  • Average shell lip thickness was highest (28 mm) near Seal Cay in the central part of the island chain, indicating that this is the oldest and least heavily exploited part of the conch population. The lowest average lip thickness (11 mm) was observed in the southern sector of the survey between Raccoon Cay and Ragged Island, revealing a very young population that is heavily exploited.
  • Shells in decades-old conch middens reflected the average size and shell lip thickness found in the surrounding living populations except in the south, near Ragged Island, where the conch landed appear to be larger than the conch observed in the surrounding living populations.
  • The estimated total abundance for the surveyed area was 6.2 million “adults” and 759,000 “subadults”. While the 2013 surveys covered approximately twice the area pre-planned, these values are probably underestimated because queen conch distribution was more extensive than the total area that could be covered during the survey period.
  • While the high density and abundance of “adult” queen onch with high average lip thickness in the Jumentos Cays and Ragged Islands is encouraging with respect to other fishing grounds in The Bahamas, the relatively low density of “subadults” suggests reason for concern.
  • Based upon the collection of data over five years in ten conch fishing grounds, there is a clear trend for local conch populations to be overfished to densities incapable of reproduction and for densities to increase with distance from human settlements. The best example of a fully functioning population other than in the Exumas Cays Land and Sea Park is the significant adult breeding population in the most remote part of the Jumentos Cays.

Recommendations

This overview of the current status of conch resources in the Bahamas leads to the following recommendations:

Bahamas Wide

  • Establish a network of marine protected areas (MPAs), fishery cooperatives and a sustainable fishery certification program.
  • Update regulations especially those related to minimum lip thickness at harvest, use of hookah (compressed air) and seasonal closure.
  • Develop area specific management plans for each major conch resource.
  • Evaluate the impact of ending export.
  • Research population connectivity using molecular genetics and the impact of discarding knocked conch in active fishing grounds.

Ragged Islands and Jumentos Cays

  • Establish an MPA in the Jumentos Cays
  • Establish a conch quota for the Ragged Islands
  • Protect southern conch populations from international poachers