32 June 2012 October and November, toward the end of the rainy season, and farmers allow about eight months for oysters to grow to market size before harvesting begins in March. Oysters are generally marketed as shucked meats in small stalls along main roads near the estuary or in local fish markets. Another shellfishery with participants that are primarily women is the fishery for the common West African blood ark clam Senilia (Anadara) senilis, known locally as cockles. Cockles are harvested throughout the year with the exception of the summer rainy season. Cockles are generally harvested by hand in sandy bottom estuaries along the Atlantic coast. Cockles are most frequently cooked whole to open the shells and sold in local markets as a cooked product. With both oyster and cockle harvesters, shells form the basis of a secondary income source when used as a feedstock in the artisanal manufacture of lime or alternatively sold and crushed as an additive for poultry feed. However, piles of oyster shells are found at all oyster processing sites near Tanbi because fuelwood for lime production is unsustainably managed and market demand for shells is far less than supply. In some areas of the upper estuary where the supply of oyster shells is less and fuelwood is abundant, lime production is a vibrant secondary industry to oyster farming (Figure 7). Early on, the Gambian Department of Fisheries recognized the potential of molluscan aquaculture as an economic development tool for the Gambia. During the late 1980s, experiments with the culture of mangrove oysters Crassostrea tulipa (C. gasar) were begun as a collaborative Fig. 7. Small-scale lime production operation in Kartong, Gambia. Empty shells of locally harvested blood ark clams are burnt using wood fires to manufacture lime for masonry mortar and other uses. Photo by Michael A. Rice. Fig. 8. Spat collector consisting of strings of ceramic tiles suspended from horizontal bamboo poles in the Tambi estuary. This photo taken mid-June 2009 shows considerable fouling by tunicates of the genus Mogula. Photo by Michael A. Rice. project between the Gambian Department of Fisheries and Dr. Gary Newkirk of the Mollusc Culture Network at Dalhousie University, with funding from the International Development Research Centre (IDRC) of Canada. The project focused on using oyster culture technology developed in Jamaica where mangrove poles were used as spat collectors (Henderson 1994). Despite this effort, the harvest of wild oysters from mangrove roots, mostly in the Tanbi Estuary near Banjul, provided a sufficient supply to satisfy existing market demand, so this effort also failed to establish oyster farming in the country (Jallow 2009). Since 2009, there has been renewed interest in the culture of shellfish in Gambia. In recognition that the domestic market for oysters in Gambia is rather modest and prices obtained for shucked oyster meats are low (typically 50 Gambian Dalasis or about US$2/ kg), effort has been applied to the development of a shellfish sanitation program based on U.S. Interstate Shellfish Sanitation Conference (ISSC) or European Union standards (Jallow 2011b). The primary aim is to boost domestic and international confidence in the sanitary quality of oysters and other shellfish grown in Gambian waters, thereby increasing demand for these products. During the dry season, many of the oyster growing areas in the Tanbi estuary would be classified as acceptable using the 70 MPN per 100 mL or 14 MPN per100 mL total coliform water quality standard of the ISSC (ISSC 2009). Efforts are also underway to use artificial oyster spat collectors to determine the location and timing of oyster spatfall and settlement of fouling organisms in oyster harvesting grounds of the Tanbi wetlands area near metropolitan Banjul. Preliminary data suggest that the primary period of oyster spatfall in the Tanbi wetlands is toward the end of the annual rainy season in September. Heaviest spatfall occurs in the southern portion of the Tanbi wetlands that remain less saline for longer periods of time than more northwesterly regions of the wetlands. Heaviest recruitment of fouling organisms on spat collectors occurs in May and June at the end of
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