Population dynamics and trophic role of the Queen Conch Lobatus gigas in the Dutch Caribbean Territories
The aim of this project is to: Improve our understanding of the ecology and life history of the Queen conch to such an extent that guidelines for a sustainable conch fishery can be outlined. Additionally, alternative exploitation scenarios, such as aquaculture/IMTA are explored.
The queen conch (Lobatus gigas) is a large marine gastropod, found throughout the Caribbean and the Gulf of Mexico. In the Caribbean region the queen conch fishery is the second most important benthic fishery. In response to the demand from the international market, landings of queen conch have increased significantly during the last decades. Consequently, several populations have been reduced (e.g., Dominican Republic, Florida Keys, Guadalupe, Puerto Rico). In response to population declines and illegal trade, in 1992 the species was included in the Appendix II of the Convention of International Trade in Endangered Species.
Therefore there is a need for strong and decisive management based on a good understanding of the species. Current understanding of the basic biology and stock are not sufficient for effective management (e.g., population connectivity, size-at-maturity is insufficiently known). Hence the aim of the project is:
Improve our understanding of the ecology and life history of the Queen conch to such an extent that guidelines for a sustainable conch fishery can be outlined. Additionally, alternative exploitation scenarios, such as aquaculture/IMTA are explored.
This aim will lead a more efficient management and a more sustainable harvest of the Queen conch populations in the Caribbean. Additionally, this project aims to improve our understanding of the tropic role of Queen conch and explore possibilities to incorporate the species in an Integrated Multitropic Aquaculture (IMTA). This in order to increase the effectiveness of the commercial cultivation of conch and making conch cultivation a long term sustainable alternative to wild caught conch.
The project consist of four parts: 1) Abundance and distribution of conch as a function of depth, habitat and fishing pressure, 2) Reproductive biology, size at maturity and spawning season of conch and the implications for fisheries management, 3) Determine connectivity within and among conch populations in the Caribbean using genetic markers, acoustic tagging of conch, and water flow modelling, and 4) Diet, role in food chain and possibilities for multi species aquaculture.
The first part will focus on assessing abundance and distribution for the three study areas (St Eustatius, Saba, and Anguilla) and setting up sustainable catch quotas. The second part will focus on the reproductive biology of conch, which will determine size-at-maturity for conch on St Eustatius, Saba Bank, and Anguilla, in relation to previous studies and suggest region-wide size limit guidelines for more sustainable harvest. The third part will focus on determine the level of connectivity between different and within different populations. This to ensure recruitment, maintain sustainable conch populations, and avoid overestimation of harvested stock which occurs along depth gradients. The fourth part will focus the tropic role of Queen conch in order to determine if conch use sponge-derived detritus as a source of nutrition and evaluate the potential for sponge and conch in an IMTA. The different parts of the project will provide knowledge to improve the management of Queen conch populations throughout the Caribbean and explore alternative exploitation scenarios for a long term sustainable alternative to wild caught conch.
Field work involves the assessment of population numbers using SCUBA-diving, and a new towed-video technique. Reproductive biology is performed by histological study of the gonad tissue in combination with external measurements of the shell. Growth will be studied in the field and through growth experiments. Stable isotopes are used for diet investigations.