The Biology, Fisheries, and Management of the Queen Conch, Strombus gigas WILLARD N. BROWNELL and JOHN M. STEVELY Introduction Cayenne (Fig. 2). Besides conch (pro­ nounced "konk"), they are also The queen conch, Strombus gigas known as botuto (Venezuela), cam­ (Fig. 1), a large marine snail, has been bombia (Panama), carrucho (Puerto a principal source of food for the in­ Rico), cobo (Cuba), guarura (Los Ro­ Figure I.-Adult queen conch, habitants of Caribbean coasts and ques), lambie (Windward Islands), Strombus gigas. islands since the first American Indians and lambi (Hispaniola). They are also settled there long ago. Today it re­ frequently called "pink conch." mains an important source of protein In some places, such as the Caicos in the region, while imports by the Bank, conchs with thick, stubby shells United States have grown. However, and leathery black skin are found. conchs. Fishermen consider them to stock depletion is now occurring in These are called "samba" or "sanga" be a different, and far less desirable, many areas due to overfishing. animal, while biologists say they are This particular conch is one of six simply a morphological variation of species of the family Strombidae Willard N. Browell is with the Complex Systems the queen conch (Randall, 1964). found in the Caribbean and Florida, Research Center, O'Kane House, University of Economically, the queen conch is New Hampshire, Durham, NH 03824. John M. now the second most valuable Carib­ and is by far the region's most impor­ Stevely is with the Marine Advisory Program, tant mollusk. Queen conchs are heavily University of Florida, 1303 17th St. W., Palmet­ bean fishery resource after the spiny fished throughout most of their range to, FL 33561. Views or opinions expressed or lobster. As a protein resource it has implied are those of the authors and do not from Bermuda and southern Florida, necessarily reflect the position of the National been second only to finfish in native all around the Caribbean, south to Marine Fisheries Service, NOAA. diets for at least 100 years. In addition ABSTRACT-Available information on the biology, FISheries, and culture ofthe queen conch, Strombus gigas, throughout its geographic range, is reviewed. Begin­ ning in the early 1970's, development ofa lucrative frozen conch meat market in the United States dramatically increased the GULF of MEXICO economic significance ofthe queen conch. However, the current condition ofseveral conch fisheries indicates that these stocks are insufficient to meet demand. Some conservation measures have been imple­ mented, but lack offisheries biology data and FISheries personnel hamper develop­ ment of comprehensive management plans. Problems with stock depletion have focused attention on the possibility of conch culture and/or stocking. In recent years a number of small, local research projects have been initiated to study queen conch biology and larval rearing. How­ ever, expanded research is needed to develop larval culture techniques appli­ Figure 2.-Geographic distribution of queen conch, Sfrombus gigas (after cable fo pilof scale hatchery operation. Warmke and Abbott, 1961). July 198/,43(7) / to the value of the meat, the brightly colored shell is often sold for orna­ mental purposes and was once used in the manufacture of lime and porcelain. Occasionally, an irritating particle lodged between animal and shell results in production of a conch pearl. Although these pearls often have high market value, demand for them is limited since they fade with age. Today, rapidly expanding human populations throughout the region have brought more modern fishing methods, more sophisticated process­ ing and marketing structures, and the queen conch has been overfished over most of its range. Catches in most areas now are not even sufficient to satisfy local demand, much less to take advantage of lucrative export Figure 3.-Strombus gigas laying eggs in 3 m (10 feet) of water off the Bahamas. markets. This paper reviews the biology and fisheries of the queen conch and also considers management and research strategies for its restora­ tion and culture. ular habitat in which conchs are immature animals in particular tend found tend to be the principal foods. to feed most actively at night, while Biology Although seagrasses such as Thalassia often spending most or all of the day are consumed, various species of buried in the sand. Habitat algae are the principal elements in the Reproduction Queen conchs commonly inhabit diet of S. gigas. Robertson (1961) sandy bottoms that are stable enough observed conchs feeding on the epi­ Copulation and spawning occur to support the growth of some of the phytic algae on Thalassia but found during the warmer months of the year numerous species of algae and sea­ no Thalassia leaves in the gut. He (Brownell, 1977; 0'Asaro, 1965; Ran­ grasses upon which they feed. They noted four species of algae that were dall, 1964), although in some areas are also found on gravel, coral rubble, ingested by Strombus: an unidentified reproductive activity may occur year and smooth hard coral or beach rock blue-green, Cladophora sp., Hypnea round (Blakesley, 1977). Fertilization bottoms. Queen conchs may be found cervicornis, and Polysiphonia sp. is internal. Under protection of the in only a few inches of water or down Conchs may ingest considerable flaring lip, the penis is extended to 76 m (250 feet), but they seldom go quantities of sand while feeding on through the siphonal notch and up deeper than 30 m (100 feet) (Randall, fIlamentous and unicellular algae into the genital region (Berg, 1975). 1964). Restriction of queen conchs to (Robertson, 1961; Randall, 1964). Randall (1964) observed conchs copu­ shallower water has generally been at­ Small benthic animals found in the lating at night as well as by day. Initial tributed to limitations of light for gut are believed to have been acciden­ copulation precedes spawning by sev­ plant growth (Randall, 1964; Robert­ tally consumed (Randall, 1964). eral weeks (0'Asaro, 1965; Randall, son, 1961). Small juvenile conchs Preliminary studies by Hesse' have 1964). ( <:: 80 mm or 3.2 inches) are often found that food preferences of the Generally, females produce egg buried in sand during the day and are queen conch change over the course masses in clean coral sand with a low rarely seen (Randall, 1964). of a year. Although probably due in organic content. Production of the part to variations in availability of egg mass (Fig. 3) takes 24 to 36 hours Food plant species, apparently there is also (Randall, 1964; 0'Asaro, 1965). The The queen conch is one of the a clear seasonal difference in the egg mass consists of a long contin­ largest of the herbivorous gastropod desirability of certain food sources. uous tube which folds and sticks mollusks (Yonge, 1932), and uses a Feeding by conch during the night together in a compact mass. Adhering long, higWy extendable proboscis to was reported by Randall (1964), and sand grains provide camouflage. The graze algae and seagrasses. number of eggs per egg mass has been In general, Randall (1964) found IChuck Hesse, PRIDE, Pine Cay, Turks and estimated at between 313,000 and that the dominant plants of a partic- Caicos Islands, B.W.I., pers. commun. 485,000 (Robertson, 1959; Randall, 2 Marine Fisheries Review Figure 4.-Top left is a four­ lobed Strombus gigas veliger showing beginning formation of third pair of lobes at 10-12 days old. Six-lobed veliger (top right) 15 days old. Below right is a settled larva just prior to metamorphosis. Foot can be seen at upper left of photo, below the shell. 1964; D'Asaro, 1965). Laying of more than one egg mass per breeding season by the queen conch and other Strombus sp. has been suggested by several investigators (Robertson, 1959; Randall, 1964; Berg, 1975). The larvae, or veligers (Fig. 4), emerge from the egg cases after ap­ proximately 5 days (D'Asaro, 1965) and immediately assume a pelagic lifestyle, feeding on small phyto­ plankton. If conditions are right, the veligers settle to the bottom at 17-22 days after hatching, although they continue to be plankton feeders (Brownell, 1977). Metamorphosis is complete (development of the probos­ cis, disappearance of velar lobes) at 28-33 days (Brownell, 1977). However, larval development can be extremely slow if the supply of phytoplankton does not provide the appropriate types and quantities of required organisms (0'Asaro, 1965; Brownell, 1977). Growth Several investigators have estimated Table 1.-Calculated lengths of queen conch at 1,2, and 3 years of age. queen conch growth rates (Table 1). Lengths (em) and years Method of calculation Estimates of mean length (tip of spire (geographic location) Reference to distal end of siphonal canal) have ranged from 7.6 cm to 10.8 cm (3 to 8.8 12.6 18.0 Size frequency distribution of natural population (Puerto Rico) Berg (1976) 4.3 inches) for yearling conch, from 7.6 12.8 18.0 Size frequency distribution ot natural popuiation (Venezuela) Brownell (1977) 12.6 cm to 17.0 cm (5 to 6.7 inches) at 10.8 17.0 20.5 Von Bertalanlfy growth curve analysis of Randall's 1964 Berg (1976) the 2-year mark, and from 18.0 cm to tag/recapture data (Sf. John. U.S.V.I.) Brownell et al. (1977) 20.5 cm (7.1 to 7.9 inches) at the end No 17.0 18.6 Von Bertalanffy growth curve analysis of nine populations using Alcolado (1976) of the third year (Fig. 5, 6). data tag/recapture data (Cuba) July 198/,43(7) 3 Figure 5.-Aphoto­ Hesse 2 and Berg (1976) estimated micrograph of a that at an age of 2.5-3.0 years the Strombus gigas ju­ venile 20 days conch stops building the shell in a after metamor­ spiral fashion and starts building the phosis (4 mrn flaring lip (Fig.