World Aquaculture December 2019

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2019 39 during harvesting (Fig. 3). In traditional harvesting areas, this resulted in a decline in oyster productivity, already under pressure from overfishing. By 1985, over 97 percent of oysters harvested were fromBoquerón Bay, southwest Puerto Rico (Appledoorn 1997). Oyster mariculture is not new to the Caribbean or Puerto Rico. Mangrove oysters have been farmed in Cuba since 1975 and, in Jamaica, mangrove oyster rafts are used to meet local demand and repopulate areas lost to development (Jory and Iverson 1985). The mangrove oyster has been successfully reared using several holding techniques. Watters and Prinslow (1975) andWatters and Acosta Martínez (1976) were among the first to evaluate the feasibility of mangrove oysters mariculture using artificial structures. Later studies used standard practices for farming other oyster species (Nascimento 1991a). Although large commercial oyster industries use hatchery stock, oyster mariculture in many countries began by using low-cost techniques to collect naturally recruited juveniles (spat) for grow-out. Small-scale artisanal fisheries such as those in Puerto Rico could benefit from such an approach. We hypothesized that the natural mangrove forest could serve as a nursery for developing spat that would be relayed to an oyster farm L ocal molluscan shellfish are a traditional and popular food in Puerto Rico and are generally consumed raw (Fig. 1). The oyster of choice is the mangrove oyster Crassostrea rhizophorae , which naturally grows on the prop roots of red mangrove Rhizophora mangle (Fig. 2). The oyster can grow at temperatures of 25-30 C. Maximum growth rates are achieved at the upper end of the temperature range and at salinities of 25-35 ppt (Mattox 1949, Lemos et al. 1994). Mangrove oysters spawn year- round and spawning appears to be triggered by sudden decreases in salinity associated with heavy rains (Watters and Acosta Martínez 1976). In Puerto Rico, this environment is typically associated with coastal lagoons and bays of the Caribbean Sea. Throughout the Caribbean, coastal development and associated anthropogenic impacts affect nearshore ecosystems (Hertler et al. 2009). Mangroves continue to be threatened throughout Puerto Rico. By 1970, nearly 30 percent of all mangroves on the island had been destroyed, with the majority of the destruction occurring between 1965 and 1970 (Heatwole 1985). This decline was attributed to an increase in wastewater discharges and extensive cutting of mangrove roots. Local fishers harvest mangrove oysters from the roots of mangrove trees, which are often removed or damaged Oyster Mariculture in Puerto Rico — A Pilot Study of Evaluation of Methods and Feasibility Heidi Hertler, Jay Levine and Graciela Ramirez-Toro ( C O N T I N U E D O N P A G E 4 0 ) FIGURE 1. Oysters and clams sold for raw consumption. FIGURE 2. Mangrove oysters settle on natural and artificial substrates. Red mangrove prop root systems are ideal for oyster settlement. FIGURE 3. Oyster harvesting can be destructive to mangrove systems. In addition to access to collecting areas, removing oysters can damage roots.