BIOLOGICAL DATA ON BERRY ISLANDS (BAHAMAS) 



QUEEN CONCHS, STROMBUS GIGAS, WITH MARICULTURE AND 



FISHERIES MANAGEMENT IMPLICATIONS 



Edwin S. Iversen,^ Edward S. Rutherford,^ Scott P. Bannerot.^ 



AND DARRYL E. JORYI 



ABSTRACT 



Biological data designed to assess the mariculture potential of queen conchs, Strombus gigas, and to 

 aid in management of stocks in the Berry Islands, Bahamas, were collected from March 1980 to February 

 1983. Juveniles congregated in shallow areas adjacent to cays with strong currents. Growth of queen 

 conchs differed among cays and seemed related to conch density. Average growth rates from several 

 cays in the Berry Islands showed that growth was slower than that reported for queen conchs in other 

 areas in the Caribbean. Estimated survival of juvenile queen conchs (about 10 cm) was 57-80% per month, 

 or 2-9% annually. Yield per recruit from this population can be maximized by harvesting the animals 

 at about 15 cm, which is the size at onset of lip formation but may be below the size at maturity. Presently, 

 potential for increasing queen conch production through intensive and/or extensive mariculture seems 

 low because of high hatchery costs, lack of dependable mass-rearing techniques, high predation on young 

 released in nature, and slow growth of penned conchs. 



The queen conch, Strombus gigas, sl giant marine 

 snail which is a major food resource in the Carib- 

 bean, Bahamas, and some Central American na- 

 tions, has been exploited by subsistence and com- 

 mercial fishermen for centuries. During the last 

 several decades, recreational conch fisheries have 

 developed and expanded considerably, placing high 

 fishing pressure on these stocks. Until recently there 

 has been little scientific research directed at improv- 

 ing production from existing stocks. The present 

 study was designed to obtain biological data to ful- 

 fill this need in the Berry Islands, Bahamas. 



Based on its high fecundity, feeding habits, limited 

 migration habits, and high market demand, queen 

 conch appears to be a desirable candidate for both 

 intensive mariculture (enclosed) and extensive mari- 

 culture (released into nature to augment natural 

 stocks) (Berg 1976; Brownell 1977; Brownell et al. 

 1976; Brownell and Stevely 1981). Success of either 

 type of mariculture is dependent upon technical 

 ability to mass-rear queen conch inexpensively from 

 eggs on a dependable basis, and on knowledge of 

 optimal natural habitats for raising juveniles to a 



'University of Miami, Rosenstiel School of Marine and Atmo- 

 spheric Sciences, 4600 Rickenbacker Causeway, Miami, FL 

 33149-1098. 



^University of Miami, Rosensteil School of Marine and Atmo- 

 spheric Sciences, 4600 Rickenbacker Causeway, Miami, FL; 

 present address: Everglades National Park, Research Center, 

 Homestead, FL 33034. 



sufficiently large size for either release in nature or 

 for grow-out for market. 



Our research on hatchery methods and potential 

 of queen conch mariculture is described in Siddall 

 (1983) and Iversen (1983), and the role of predators 

 in limiting the size of conch populations is described 

 in Jory (1982), Jory and Iversen (1983), and Iversen 

 et al. 1986. Much of the information needed to assess 

 feasibility of increasing queen conch production 

 through mariculture is directly relevant to manage- 

 ment of wild stocks. Specific objectives of the Berry 

 Islands field work were to obtain data on age and 

 growth, survival, and optimal habitat for rapid 

 growth and high survival of early life stages. Based 

 on this information, we make recommendations for 

 management of wild stocks. 



Our study area, the Berry Islands, lies on the 

 northeastern edge of the Great Bahamas Bank (lat. 

 25°35'N, long 77°45'W) about 190 km east of Miami, 

 FL (Fig. 1). This area is characterized by small cays, 

 shallow sand flats (2-4 m deep) with abundant turtle 

 grass, Thalassia testudinium, beds. The 30 plus 

 islands are located on the west side of the N.E. Pro- 

 vidence Channel and north of the Tongue of the 

 Ocean. The islands are generally low-lying and 

 covered with dense undergrowth, Australian pines, 

 and palm trees. Tidal currents, frequently quite 

 strong, set in and out of the openings between cays. 

 Most cays are privately owned and sparsely popu- 

 lated. 



Manuscript accepted December 1986. 

 FISHERY BULLETIN: VOL. 85, NO. 2, 1987. 



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