BIOLOGY OF THE QUEEN CONCH

There are six species of conch throughout the Caribbean and Florida waters that belong to the family Strombidae: Strombus gigas, S. costatus, S. raninus, S. alatus, S. pugilis, and S. gallus. These large gastropods inhabit the shallow seagrass beds of Florida, the Bahamas, the Caribbean Islands, Bermuda and the coast of Central and South America. Conch are marine gastropods with spines on the spire and a lipped aperture. The conch species can be categorized by their shell length (SL), which is obtained by measuring the shell from the siphonal canal to the apex of the spire. The modified foot is used for a unique type of locomotion. They use the hardened tip of their foot, the operculum, to propel themselves forward in a "hopping" motion commonly referred to as a strombid leap. This movement is thought to help the conch make a quick escape from predators and also breaks up their scent trail. Their muscular eyes are located at the tip of stalks and they have a long proboscis for feeding.

Queen conch, Strombus gigas, with its large lipped pink shell (25 cm or 9 inches SL), has the highest commercial fisheries value of the six species. Numerous studies have focused on fisheries management, ecology, and culture techniques of queen conch. In the wild, adult queen conch maintain a 1:1 sex ratio in an undisturbed population, and do not reach sexual maturity until their shell lip is fully developed at 3-4 years of age. The queen conch demonstrates seasonal reproduction, which varies throughout its geographic locations. The typical 6 - 8 month egg-laying season is between March and October.

During the reproductive season, large aggregations of conch will migrate towards shallow water (10m (3.5 ft) or less) and breed in coarse sandy habitats near reefs and seagrass Thalassia testudinum beds. The conch have separate sexes and internal fertilization. The female lays a crescent shaped egg mass which contains up to 400,000 eggs. Females can lay an average of 9 egg masses per season or an estimated 3 to 4 million eggs per season. A female conch camouflages the egg mass with sand grains to help ensure its survival through the three to four day incubation period. When the egg mass hatches, the planktotrophic veligers will progress through a three to eight week cycle of stages while drifting in the water column.

Once the veligers are morphologically ready (1-2 mm SL), they will respond to a trophic cue and settle on or near a seagrass bed and undergo metamorphosis into a fully benthic animal. The juvenile conch will remain buried for the majority of their first year of life, possibly as a means to avoid predation. As herbivorous gastropods, the juvenile and adult conch will feed on a variety of algae, detritus, and diatoms that are commonly found on sand, seaweed, and seagrass blades. During the first couple of years, the juvenile conch will begin to add length to their shell. After 2.5 - 3 years of age, the juvenile stops adding shell length and begins to add shell to form the flaring lip. At this time, the conch will become a sexually mature adult, and begin the cycle all over again.