Wilson et al. (2005) investigated the use by fish of discarded Queen Conch shells, both single shells and middens (piles of shells discarded by fishermen). Although not all isolated shells were occupied by fish, all conch middens examined harbored fish. Fish species found within conch shells included many of the ecologically important herbivores, such as scarids and pomacentrids, as well as lutjanids, haemulids, and serranids which are exploited by fisheries throughout the Caribbean. Furthermore, juvenile fish showed a preference for conch shells over other microhabitats in three of the four habitat types surveyed. In the course of their study, Wilson et al. observed 9 species of fish from 6 different families in individual conch shells; in middens, they recorded shell use by 42 fish species representing 16 families. Although the main use of the conch shells was for shelter, on several occasions Stegastes species had laid eggs on the clean inner surface of conch shells and the goby Gnatholepis thompsoni was observed guarding egg clutches placed under the lip of shells. Conch shells may therefore represent important reproductive sites for fish. Fish abundance and species richness increased with midden size.
Ray-Culp et al. (1997) collected potential conch predators from conch nursery areas and tested them in the lab for their ability to kill newly settled Queen Conch. They tested species from 10 families of polychaetes, 8 families of crustaceans, 4 families of mollusks, and 2 families of fishes. Conch kills were made by calappid, portunid, majid, and hermit crabs; alpheid and palaemonid shrimps; panulirid lobsters; file fish; and five families of polychaete worms (glycerids, nereids, sigalionids, spionids, and syllids). Species from five families of polychaete worms (dorvilleids, glycerids, lumbrinerids, nereids, and phyllodocids) also killed competent (i.e., ready-to-settle) conch veliger larvae.
Over the long term, conch escape predation by outgrowing their predators, but larvae and young newly settled juveniles are highly vulnerable to predation Although small conch can leap away from some threats of immediate danger using their opercula, they cannot outrun highly mobile surface predators such as crabs. Studies by Ray-Culp et al. (1999) suggest that xanthid crabs and similar small predators may play an important role in structuring Queen Conch dynamics through their predation on newly settled conch.
The Queen Conch (Strombus gigas) is a large gastropod mollusk. Its shell is among the largest in the Florida-Caribbean area and has long been a favorite of collectors and souvenir hunters. Conch meat is an important food source in the West Indies. Overfishing for souvenirs and food has severely depleted Queen Conch populations in many areas. (Rehder 1981)
The Queen Conch (Strombus gigas) supports important fisheries in the Caribbean. Unfortunately, the species has become so depleted that it is currently listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II (Appendix II lists species that are not necessarily now threatened with extinction but that may become so unless trade is closely controlled). The Queen Conch once also supported commercial and recreational fisheries in south Florida. However, the ease of capture and desirability of the shell and meat resulted in a severe depletion of the local population to the point that in 1985 a total harvest ban was instituted in state waters and in 1986 in federal waters. After the ban was established, fewer than 6000 adult conch remained in the Florida Keys. Since then, ongoing surveys have shown a slow and very limited recovery with an estimated 25,500 adults in 2006. (Delgado and Glazer 2007 and references therein)
For some species, per capita population growth rate may become negative when population density drops too low (e.g., if low population density means that individuals cannot find mates or be properly stimulated to mate), so that below a certain population density a population may go into a tailspin. This is known in ecology as the "Allee Effect". Stoner and Ray-Culp (2000) examined the effect of adult Queen Conch population density on reproductive behavior. They surveyed adult density, reproductive behavior, and spawning in natural Queen Conch populations at 2 locations in the Exuma Cays, Bahamas. They found that mating never occurred when density was <56 conch per hectare, and spawning never occurred at <48 conch per hectare. Reproductive behavior increased rapidly to asymptotes at densities near 200 conch per hectare (i.e.,the effect of population density above 200 individuals/hectare was very slight). Heavily exploited populations of queen conch in the Caribbean have been slow to recover despite fishery closures. The findings of Stoner and Ray-Culp suggest that the failure of Queen Conch populations to recover might be attributable at least in part to spawning stock densities having being reduced to the point at which Allee effects begin to impact reproductive behavior.
The Queen Conch (Strombus gigas) occurs from southeastern Florida to the West Indies and Venezuela (Rehder 1981).
The Queen Conch (Strombus gigas) occurs in Bermuda and south Florida through the West Indies (Morris 1973).
The Queen Conch (Strombus gigas) is found from south Florida to Brazil (Abbott 1968).
Delgado et al. (2002) conducted a series of experiments in the lab showing that exposing hatchery-reared juvenile Queen Conch to a predator (the spiny lobster Panulirus argus) resulted in behavioral changes, and apparently even changes in shell density or thickness, that made previously exposed conchs less vulnerable to predatation in subsequent predation trials.
High-density aggregations of juvenile Queen Conch are sometimes observed on nursery grounds. Stoner and Lally (1994) argue that these animals aggregate to reduce the probability of any particular individual being attacked by a predator.
Glazer et al. (2003) studied the home ranges of adult Queen Conch at two sites in the Florida Keys. Mean home range was 5.98 hectares, with more movement during the summer.
The Queen Conch (Strombus gigas) is found in sand and rubble, usually in or near eelgrass, in water 1.5 to 3.5 meters deep (Rehder 1981).
The Queen Conch (Strombus gigas) is found in shallow water (Morris 1973).
The Queen Conch (Strombus gigas) is found on sand and eelgrass at depths from less than a meter to 9 meters (Abbott 1968).
The status and trends of regional Queen Conch fisheries led to listing of the species on Appendix II of the Convention on International Trade in Endangered Species (CITES) in 1990. The International Union for the Conservation of Nature (IUCN) categorized the species as “commercially threatened” on the 1994 Red List. More recently, the CITES Authority imposed a suspension of the export trade from the Dominican Republic, Honduras, and Haiti in 2003 based on evidence for declining stocks and the absence of an effective regulatory framework. In 2004, additional suspensions were implemented for
Antigua and Barbuda, Barbados, Dominica, and Trinidad and Tobago. Fisheries in 13 other countries were categorized as “of possible concern.” (Acosta 2006 and references therein)
The pelagic larvae of the Queen Conch live in the water column for 18 to 28 days before they settle and metamorphose on the sediment. Little is known about early stages of the benthic (post-settlement) life of the Queen Conch. However, 1 year-old juveniles (80 to 100 mm shell length) are believed to emerge from the sediment and feed in seagrass beds that provide abundant algal and detrital foods. Sexual maturity is reached at approximately 3.5 yr of age (180 to 270 mm shell length), which is preceded by the development of a flared shell lip. (Stoner and Lally 1994 and references therein)
Queen Conch (Strombus gigas) that inhabit the nearshore waters of the Florida Keys are physiologically incapable of reproduction even when they have reached reproductively active sizes (Delgado et al. 2004). In addition, these conch are isolated from offshore breeding aggregations by the poor conch habitat in Hawk Channel, a naturally occurring deep-water channel that runs parallel to the Keys between the island chain and the offshore reef tract. The substrate on the bottom of Hawk Channel is predominantly soft sediment, which is poor conch habitat. This channel thus serves as a barrier to migration, isolating nearshore from offshore conch aggregations. Queen conch in other areas undergo ontogenetic migrations from shallow, nearshore sites to offshore habitats, but conch in the Florida Keys are prevented from doing so by Hawk Channel. Efforts to artificially connect the inshore and offshore areas isolated by Hawk Channel, however, have yielded encouraging resuls. Conch translocated from nearshore habitats into offshore breeding aggregations become reproductively active within just a few months (Delgado et al. 2004). The success of translocation efforts suggests that some component of the nearshore environment (e.g., pollutants, temperature extremes, poor food or habitat quality) disrupts reproduction in conch, but that removal of nearshore animals to suitable offshore habitat can restore reproductive viability. These results indicate that translocations are preferable to releasing hatchery-reared juveniles because they are more cost-effective, result in a more rapid increase in reproductive output, and maintain the genetic integrity of the wild stock. Translocating conch from nearshore larval sinks to offshore larval sources (spawning aggregations) may be the key to expediting the recovery of queen conch stocks in the Florida Keys. (Delgado et al. 2004; Delgado and Glazer 2007)
Queen conch is harvested in over 25 Caribbean countries, but fishery regulations vary considerably. For example, regulations may include shell size and/or meat weight limits (Bahamas, Bonaire, Puerto Rico and the U.S. Virgin Islands, St. Kitts and Nevis, St. Vincent and the Grenadines, Turks and Caicos Islands), closed season (Mexico, Puerto Rico and the U.S. Virgin Islands, Venezuela), and prohibition of fishing using scuba technology (Turks and Caicos Islands). Some countries (Bahamas, Dominica, Panama) have set landings or export quotas, but verification is difficult due to insufficient monitoring and reporting. A few countries have no fishery regulations or management plans for this species. (Acosta 2006)
The shell of the The Queen Conch (Strombus gigas) is large and heavy. It is yellowish white with irregular brownish markings. Fresh shells have a thin, brown periostracum (the outermost layer of most mollusk shells) that flakes off when dry. The spire is high and strongly angled, with pointed knobs where obscure axial ribs cross angles; the knobs on the last 3 whorls are large and pointed. The interior of the outer lip and the aperture are pinkish, suffused with white or yellow. The outer lip has a broad upper expansion that is generally as high or higher than the spire; the lower half is somewhat wavy. Immature shells look quite different, with a high spire of strongly angled whorls, a narrow pointed base, and an unexpanded lip. (Rehder 1981)
The shell of the adult Queen Conch (Strombus gigas) is heavy and solid with a short conical spire. It is mostly body whorl, with an aperture that is moderately narrow and channeled at both ends. The outer lip is thickened and greatly flared in fully grown specimens. There are 8 to 10 whorls, with blunt nodes on the shoulders. The operculum is clawlike and horny. The shell is yellowish buff, with a bright rosy pink interior. Young specimens have zigzag axial stripes of brown. (Morris 1973)
The Queen Conch (Strombus gigas) may reach a height of 20 to 30 cm and exceed 2 kg in mass (Morris 1973).
