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Habitat
Queen conch commonly inhabit sandy bottoms that are able support the growth of some of the numerous species of algae and seagrasses that they feed upon. The pelagic queen conch veliger spends 18 to 40 days in the water column. The larvae then settle and metamorphose in the shallow warm water benthos. Queen conch may be found in only a few inches of water or down to 70m, but seldom go below 30m. Despite high densities of 1 and 2 year old conch (80-140mm length) in seagrass meadows, early juveniles less than 60mm length have rarely been seen in the field. These early juveniles are assumed to spend a large portion of the time buried in the coarse sand, emerging for short periods at night and remaining buried throughout the day. The amount of time buried diminishes with increased age and size. Food limits and increased effort for burrowing lead to a continuous epifaunal existence for conch at approximately one year of age. These juvenile conch are usually associated with seagrass beds adjacent to the shallow, coarse grained sand bars that they previously inhabited. These seagrass beds are usually dominated by two species, Thalassia testudinum and Syringodium filiforme. Older and larger conch can be less selective of their habitat and are thus found over a wider range.
Reproduction
The sexes are separate and the female conch reaches sexual maturity at approximately 3.5 years of age, just a few months after the flared lip of its shell is formed. Fertilization is internal and copulation may precede spawning by several weeks. An individual female may spawn up to 9 times in a single reproductive season that lasts from May to November. The season is completely dictated by changes in water temperature. An egg mass usually takes 24 -36 hours to produce and consists of a single continuous egg-filled tube folded over upon itself to form a croissant shaped collection of eggs. It is estimated that anywhere from 350,000 to 500,000 eggs are contained in a single egg mass.
Feeding
The queen conch is one of the largest herbivorous gastropod mollusks, and uses a long highly extendable proboscis to graze algae and sea grass. The pelagic larvae of S. gigas do not show a preference in photoperiod for feeding and ingest a variety of alga. The most common algae ingested have been Isochrysis sp. and Tetraselmis sp., but over 21 different alga species have been detected in conch veligers.
The dominant plants of a particular habitat in which queen conch are found tend to be the principle foods. Although sea grasses such as Thalassia testudinum are consumed, it is only a by-product of grazing various forms of algae and detritus from its blades. Some of the most common algae ingested are Cladophora sp., Hypnea cervicornis, and Polysiphonis sp.. The diet of S. gigas also changes with the seasonal migrations offshore and inshore.
Movement/Migration
Queen conch exhibit movement and migration of the population inshore during the Spring and offshore during the Autumn months. This migration is more age dependant with increased frequency and range with increased age. Queen conch tend to show limited migration in the Winter, choosing to bury for extended periods of time. The adult queen conch has a large home range with estimates ranging from 2 to 8 kilometers per season.
Predation
Known and potential predators of S. gigas include several species of gastropods, cephalopods, decapods, elasmobranch and teleost fishes, and marine turtles. The best defense for the queen conch is size; therefore the largest prey class is the juvenile conch up to one year. This age class has just emerged from a predominately buried lifestyle and is easy prey for all species of predators. As the conch is able to age and increase its shell size, it is able to reduce the number of predators that can penetrate the shell to its meat. Shell morphology also limits certain predators to certain life-stages of conch. The spires that grow in whorls on the conch shell protect it from small mouthed predators. The spires also serve to deflect much of the crushing pressure exerted by certain predators over a larger area of the shell. Sea turtles, nurse sharks, porcupine fish, rays, and larger crab and lobster are able to use their powerful claws, mandibles, and specialized dentition to crush the shell in order to gain access to the meat. Marine snails such as the tulip snail, Faciolaria tulipa, and the apple murex, Murex pomum, are are able to predate upon smaller age class conch. These snails are able to pry open the aperture protected by the operculum and enter the conch shell. Once inside they devour the conch meat by scraping with their radulae, usually leaving the entire shell intact. There are three other methods used by predators to eat conch. Certain crabs and the spiny lobster, Panulirus argus, peel and chip the shell in a spiral pattern to reach the meat. Another common predator is the octopus. The octopus is able to prey on larger age classes of conch due to it's method of entry. They drill a hole in the spire of the shell and inject a neurotoxin which renders the conch unconscious. It is then able to slip inside the shell and feed on the soft tissue. However, the queen conchs most active and devastating predators are humans.
Historically sailing sloops were used for harvesting conch. The ship would sail to a good fishing area where several men would fish from small dinghies. The bottom was scanned using a glass bottom bucket until a conch was spotted. These men originally used poles to then hook the conch and bring it to the surface. These trips would last several days with the captured conch either being kept live in wells or sun dried and cured with salt. Presently, small boats with outboard motors have become necessary with the need to reach more distant fishing areas. The boats usually carry 2-3 men and their gear. Most men are free divers and use only mask fins and snorkel in order to reach conch up to 8m deep. A good diver can carry at least 8 conch in his hands in any one dive. The shells are discarded at the fishing site allowing the boat to bring more meat to market each day. Current available technology is allowing the daily catch to be increased at an unsustainable rate, thus forcing governmental fisheries departments to close conch processing plants earlier every year.
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