VARIATION OF VELIGER HATCHING, DEVELOPMENT, AND GROWTH FROM FIVE Strombus gigas QUEEN CONCH EGG MASSES: FOR RESTORATION IN THE BAHAMAS

The Queen Conch, Strombus gigas, is a marine gastropod that lives in the warm waters of southern Florida, the Caribbean and Bermuda. Due to the high demand for this species there has been a steep decline in the population numbers in the past 40 years. To help manage the fisheries, the queen conch was listed as a CITES II species (Conservation of International Trade of Endangered Species of Wild Fauna and Flora) in 1992.

Since the 1970's many laboratories and one commercial conch farm developed cultured techniques to grow conch for food and restoration. In 2016, a new experimental hatchery was built on Hummingbird Cay, Great Exuma, Bahamas with the purpose to culture conch for restoration in the Bahamas. The initial experiments investigated the viability of the new hatchery by conducting studies that observed conch egg mass hatch rates and veliger (larval) growth and development. A total of five egg masses were collected from two locations.

The conch egg masses hatched 4 to 6 days after they were laid. The embryos were well developed with velar lobes, shell, and pigmentation on the day of hatch (see photo A.). Hatching occurred in the early evening hours and depending on the egg mass, 35-100% of the eggs hatched on the first night.  Average growth rate of veligers varied depending on the source of phytoplankton fed and the egg mass. The range for the first four days was 25 - 50 μm per day. In the first four days the veligers develop from the two velar lobe stage to four velar lobes with the beginning of the sixth set of lobes showing (see photo B.).

Culturing queen conch in the new hatchery demonstrated that there is variation between egg masses and veliger growth and development from different egg masses. Since restoration of a species requires this type of genetic variation, it is recommended that several conch egg masses from nearby locations should be used in a conch restoration program.