II. HABITAT AND DISTRIBUTION
Strombus gigas is native to north and Central America. It is encountered
along the Atlantic coast from South Carolina to the Florida Keys and in the
Caribbean Sea and the Bahamas islands at depths from 0.3 to 18 m. S.
gigas migrates en masse in offshore directions moving in a flood tide
direction (Stoner et al. 1988, Stoner and Lally 1994). Juvenile queen conch
are found in shallow, inshore seagrass meadows whereas adults are found in
deeper algal plains and seagrass meadows distinct from juveniles (Stoner 1989).
Juveniles move in large aggregations that most likely afford them protection
from predation (Stoner and Lally 1994).
Juvenile Strombus gigas occur in the shallow seagrass beds of the Indian River Lagoon.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Queen conch reach sexual maturity at approximately 3 1/2 to 4 years reaching a
shell length of at least 180 mm and up to 5 pounds (Stoner 1989). Juvenile
shells reach a length of 50 to 70 mm in the first year before they emerge from
the sand (Stoner et al. 1988). The maximum reported size is 352 mm.
Strombus gigas are recorded to live 6 to 7 years and as long as 20-30
years in deeper waters.
Densities of juvenile queen conch are usually 1 conch per meter square but have
been recorded as high as 2.1 per meter square (Stoner et al. 1988). In
southern Exuma Cay in the Bahamas, the average density of the conch was
reported to be 1.72 per meter square in 1984 (Wicklund et al. 1991). Two year
old queen conch have been observed to aggregate in even greater densities
during periods of heavy wave action (Stoner 1989).
Strombus gigas moves by a unique shell-thrusting motion called "leaping"
(Hesse 1980). The queen conch uses its claw-like operculum to dig into the
sand and then "pole" forward by extending the foot (Rupert and Barnes 1994).
This is a very different mode of transportation from other gastropods.
Adult queen conch migrate to shallow, warmer inshore waters to mate and lay
their eggs (Stoner et al. 1988). The peak reproduction period is from April to
August. The queen conch lay between 180,000 - 460,000 eggs in gelatinous
strings some as long as 50 -75 feet. Females may spawn many times during a
reproductive season (Stoner et al. 1996).
Planktotropic (feeding) larvae emerge and travel long distances in the water
column (Davis et el. 1993). At approximately 18 days, the swimming veliger
shifts to a swimming/crawling stage that allows it to move along the substratum
and find an appropriate place to settle and metamorphose (Davis 1994).
Metamorphosis occurs in response to environmental cues from algae and
seagrasses (Davis 1994). After larval recruitment, metamorphosis, and
settlement of plantonic larvae, the juveniles live in the sand for the first
year until they reach 5-10 cm (Stoner et al. 1988, Stoner 1989). Once the
juveniles emerge, they move to the seagrass beds to feed on plant detritus and
algae, staying there for the next 2 years (Stoner et al. 1988, Stoner 1989).
IV. PHYSICAL TOLERANCES
Increases in the metamorphosis of Strombus gigas veliger larvae are
observed at elevated seawater temperatures of 37-38°C (Boettcher 2005).
There are no reports specifically addressing the affects of salinity
fluctuations on adults, juveniles, or larvae of the queen conch.
V. COMMUNITY ECOLOGY
Strombus gigas is an herbivore, feeding on detritus, macroalgae, and
epiphytes (Ray and Stoner 1995). The green macroalga Batophora oerstedi
appears to be a preferred food.
A small cardinal fish can sometimes be found living within the mantle of the conch.
Strombus gigas has been historically used by the Mayans, Arawak and
Florida Indians for food and tools (Stoner et al. 1988). They are still highly
valued as an inexpensive and nutritious food source in the Caribbean. Queen
conchs are also highly prized for their shells and are the target of heavy
fishing in tourist areas. In addition, they are cultured in western Montana
for medicinal purposes.
Queen conch populations are declining throughout their geographic range and, in
some regions stocks have collapsed. In the United States, fishing for S.
gigas is illegal and in Puerto Rico and the Virgin Islands the fishery is
regulated by the Caribbean Fishery Management Council. In the Caribbean, the
queen conch commercial fishery is estimated at 60 million U. S. dollars
wholesale. A detailed report of the global net exports of queen conch from
1992-2001 is available online from CITES.
Davis M. 1994. Short-term competence in larvae of queen conch Strombus
gigas: shifts in behavior, morphology and metamorphic response. Marine
Ecological Progress Series 104:101-108.
Davis M, Bolton CA, and AW Stoner. 1993. A comparison of larval development,
growth, and shell morphology in three Caribbean Strombus species.
Hess KO. 1980. Gliding and climbing behavior of the queen conch, Strombus
gigas. Caribbean Journal of Science 16:1-4.
ITIS. Integrated Taxonomic Information System. Available online.
NOAA Office of Protected Resources. Available online.
Ray M and AW Stoner. 1995. Growth, survivorship, and habitat choice in a newly
settled seagrass gastropod, Strombus gigas. Marine Ecological Progress
Rosenberg G. 2005. Malacolog 4.1.0: A Database of Western Atlantic Marine
Mollusca (version 4.1.0). Available online.
Rupert, EE and RD Barnes. 1994. Invertebrate Biology, Sixth Edition. Harcourt
College Publishers, Fort Worth, TX pg. 395.
Stoner AW. 1989. Winter mass migration of juvenile queen conch Strombus
gigas and their influence on the benthic environment. 56:99-104.
Stoner AW and J Lally. 1994. High-density aggregation in queen conch
Strombus gigas: formation, patterns, and ecological significance.
Marine Ecology Progress Series 196:73-84.
Stoner AW, Lipcius RN, Marshall LS Jr., and AT Bardales. 1988. Synchronous
emergence and mass migration in juvenile queen conch. Marine Ecological
Progress Series 49:51-55.
Stoner AW, Ray M, Glazer RA, and KJ McCarthy. 1996. Metamorphic responses to
natural substrata in gastropod larvae: decisions related to postlarval growth
and habitat preference. Journal of Experimental Marine Biology and Ecology
Wicklund RI, Hepp LJ, and GA Wenz. 1991. Preliminary studies on the early
development of the queen conch, Strombus gigas, in the Exuma Cays,
Bahamas. Proceedings of the 40th Annual Gulf and Caribbean Fisheries Institute
Melany P. Puglisi, Smithsonian Marine Station
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