Surveys of Queen Conch Populations and Reproductive Biology
Field work conducted by Community Conch during 2012 in the Bight of Abaco had two principal objectives:
1) to survey the density, abundance and population structure of queen conch stocks in the shallow commercial fishing grounds off Sandy Point and More’s Island
2) to further explore relationships between queen conch shell lip thickness (an index of age) and reproductive maturity and compare it to similar data collected in 2011 near Warderick Wells (WW) in the Exuma Cays Land and Sea Park.
Findings
- Average “adult” queen conch densities were the lowest found by Community Conch in four years of surveying commercial conching sites in The Bahamas.
- Analysis of the gonad tissues from 57 queen conch collected during the spawning season of 2012 showed that most male conch do not reach sexual maturity until their shell lip thicknesses reach 10mm (more than 3/8”). Most females were not sexually mature until the shell lip thickness was 15mm.
- Average lip thickness ranged from 6 mm in the Sandy Point area to 9 mm west of More’s Island indicating very young populations.
- Average shell length were comparable to conch measured on the banks in the Berry Islands, off Lee Stocking Island and Warderick Wells and a little larger than those found off the Grassy Cays south of Andros.
- In 202 tows, only three mating pairs were observed during the height of the reproductive season.
Conclusions and Recommendations
Three observations suggest that queen conch in the Bight of Abaco are severely overfished:
- densities of flared-lip individuals are extremely low, well below the minimum threshold required for reproduction,
- the age structure of the populations at both Sandy Point and More’s Island is very young, with very few individuals ≥ 15 mm LT,
- only three mating pairs were observed among more than a thousand flared lip conch encountered during two weeks of survey work in the middle of the reproductive season.
Given the extremely low densities and low total numbers of queen conch in the Bight of Abaco, and almost total absence of reproductive behavior, it is clear that a rebuilding program is needed for both the Sandy Point and More’s Island fishing grounds. The following measures could be considered:
- Partial or total closure of the fishing grounds until densities reach 100 adults/ha.
- End the use of compressed air for conch fishing or at any depth out of lobster season.
- Establish a total allowable catch at the fishing grounds and monitor it.
- Institute a closed season for conch fishing.
