Population status and reproductive biology of queen conch (Lobatus gigas) in the coastal waters around St Eustatius
The queen conch (Lobatus gigas) is under pressure and has decreased in distribution and abundance as a result of fisheries in the Caribbean region. To ensure sustainable fishery, knowledge on the population dynamics of this species is required. Therefore, this research focused on the status and the reproductive behaviour of the conch population around St Eustatius and provides information about the possibilities for a sustainable fishery. Conch distribution and abundance, population structure, reproductive activity and fishing pressure were determined in the coastal waters around the island of St Eustatius by dive surveys, towed video surveys, reproduction surveys and fishery catch surveys. The study covered the entire Statia National Marine Park waters and covered different habitats and depths up to 40m.
The study shows that the queen conch is abundant around St Eustatius, with mean densities of 57 (dive surveys) and 115 (video surveys) adults per ha. The total adult queen conch stock was estimated to be 184,100 (95% C.I.: 77,586-390,000) in 2,700 ha Marine Park. Further, a higher conch abundance was found on rubble habitats and at greater depths (17-31 m). Mainly mature conchs were detected, indicating a shortage of recruitment of young conch, or a difficulty in observing young conch. Further, reproductive activity started in March and declined after October, with peak reproductive activity during June and July. Minimum lip thickness reported for reproductive behaviour was 9 mm. However, this study also indicated that more research is necessary to qualify the exact spawning season and size at maturity of conch around St Eustatius.
In conclusion, the status of the queen conch could be qualified as good and does not seems to appear under direct pressure in the coastal waters of St Eustatius. With this population status, small- scale fishery may be possible without negative consequences for the queen conch population. However, to ensure long-term sustainable of a conch fishery, harvest restrictions as advised by the queen conch working group are recommended to be used; like a minimum of 15 mm lip thickness, closed areas and an annual harvest of maximal 6200 adult conch. Thus, non-detrimental fishing is possible for queen conch on St Eustatius, under the conditions that, proper management and harvest restriction regulations need to be developed, implemented and enforced in close co-operation with stakeholders.