28 SEPTEMBER 2016 • WORLD AQUACULTURE • WWW.WAS.ORG in Zanzibar, converging with the high potential of farming sea cucumbers in Tanzania (Mmbaga and Mgaya 2004, Lovatelli 2004). Crab Fattening In Zanzibar and Tanzania in general, crab farming is done by fattening mangrove crablets collected from the wild. The species farmed is the mangrove crab Scylla serrata, using cages/pens and fenced enclosures. Seed is collected from the wild or purchased from fishermen for US$ 0.20-0.40/crablet of 100-150 g. The fattening cycle ranges from two weeks to three months, depending on the size of the crablet at stocking. There are eight farmer units engaged in crab fattening (Fig. 3) and the current production level is unknown. Crabs are sold fresh-live and the market price of crabs is US$ 1-17/piece, depending on the selling size and location. Higher prices can be obtained in Unguja because of high demand in tourist hotels. Other Potential Species In Zanzibar there are plans to farm other finfish species in cages rather than the currently used earthen ponds. Finfish species that have been identified for farming are cobia Rachycentron canadum and African pompano Trachinotus sp. The Ministry of Fisheries and Livestock is working with several partners to start marine finfish farming in cages. Trials with sponge farming have been underway for more than two years in the southeast coast of Zanzibar (Jambiani) with promising results (Vaterlaus and Bumbak 2011). When disseminated to farmers, sponge farming can be another source of income for coastal Zanzibaris. The IMS has been experimenting with two seaweed species in Makoba Bay between 1996 and 2005. The species are the agarproducing red seaweed Gracilaria cornea and the green Ulva reticulata, cultivated for biofiltration of fishpond effluent water (Msuya and Neori 2002, Msuya et al. 2006). Other Gracilaria species (G. edulis and Gracilariopsis) have been evaluated and their potential for agar production has been demonstrated (Buriyo and Kivaisi 2003). Recently there has been interest in other species such as the brown seaweed Sargassum and Turbinaria and the green seaweed Caulerpa triggered by demand from Chinese markets. Seaweeds have also been integrated with shellfish and sea cucumbers (Beltran-Gutierrez et al. 2014) as a sustainable production option. Challenges Challenges faced by farmers engaged in aquaculture in Zanzibar are: • The price that farmers receive for seaweed is considered low and not fair compensation for the work done to produce the crop. • Cultivated seaweed can become severely fouled by blue-green algae, wild seaweed, and other epiphytes. This happened in 2012 and has been a persistent problem in many seaweed farming areas, perhaps exacerbated by climate change impacts such as greater surface seawater temperature and input of land-based sources of nutrients (Msuya and Porter 2014, Hayashi et al. 2010). • There is a lack of fingerlings for aquaculture. Collecting from the wild is not sustainable and thus hatcheries are important. The government of Zanzibar has partnered with the Korean International Cooperation Agency (KOICA) and the Food and Agriculture Organization (FAO) of the United Nations to start a milkfish/sea cucumber hatchery. • Theft, mainly for animal aquaculture. • There is a shortage of land and suitable sites for animal aquaculture. • Heavy rains cause low salinity that leads to high mortality. • Pond dikes may breach during extreme spring low tides. The tidal range in Zanzibar is more than 4 m and during extreme low tides the pond dikes could break even if they are properly made. • There is a lack of markets or these are limited. This is a crosscutting challenge for all forms of aquaculture. • There is spare, inaccurate, or a lack of aquaculture data, mainly caused by a shortage of technical staff to do routine data recording. Concluding Remarks This article has shown that aquaculture, as indicated by the number of farmer units and production, is increasing in Zanzibar. Although seaweed farming has been practiced for close to three decades, animal aquaculture is now increasing quickly, despite its recent introduction. Pemba produces well above 75 percent of total animal aquaculture production and 91 percent of seaweed in Zanzibar. There are marked differences in the gender of seaweed farmers on the two Islands, with more women farmers in Unguja (93 percent) than Pemba (36 percent). There are challenges for all types of aquaculture and these must be addressed to pave the way for greater aquaculture production in Zanzibar. An alternative species (Gracilariopsis) for seaweed farming growing naturally in Pemba, Tanzania. A seaweed farmer tying seed to culture lines.
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