There is a growing demand for wild caught juvenile fish to supply the market for aquaculture. However, little is known about the genetic effects of juvenile collection from wild populations. There are a number of imminent threats to both aquaculture systems and wild fish populations. Juvenile collection from a single population can for example reduce population’s evolutionary potential as well as the disease resistance within an aquaculture pond. In this study, we investigated the local genetic structure of juvenile mullets collected from five sites around Bagamoyo (Tanzanian mainland) and Zanzibar Island, East Africa. Fish were caught in low tide using a seine net. The fish were morphologically identified, and then genetically identified using direct sequencing of the CO1 gene with cross referencing with the Barcode of Life Database (BOLD) systems.  Molecular variance analyses were used to infer genetic subdivision based on geographic sampling site as well as inferring population structure through the Bayesian assignment test implemented in STRUCTURE 2.3. Our results showed that samples morphologically identified as Mugil cephalus where in fact Valamugil buchanani and we also found evidence of an introgression genome event, where the gene flow from one species may have affected the general gene pool. The Bayesian analysis revealed a clear genetic population structure among the sampled fish; the main difference was the presence of a unique mainland cluster. Our findings may have important implications for management and conservation of mullet fishes in the region and elsewhere.

Abstract—Uncontrolled growth of sea urchin populations may have a negative effect on coral reefs, making them barren. To avoid this, different methods of sea urchin reduction have been developed but, without knowledge of their genetic structure and connectivity, these methods may be ineffective. The aim of this study was to examine the fine-scale genetic structure and connectivity in the sea urchin, Diadema setosum, population around Unguja, Zanzibar, using AFLP. We found evidence of different genetic clusters, high migration between the sites and high genetic diversity within the sites. These findings indicate that a manual reduction of sea urchins with similar genetic connectivity, implemented on the same geographic scale as our study, would be ineffective since sites are probably repopulated from many sources.

The bacterium causing cholera, Vibrio cholerae, is essentially a marine organism and its ecological dynamics have been linked to oceanographic conditions and climate. We used autoregressive models with external inputs to identify potential relationships between the number of cholera cases in the coastal regions of mainland Tanzania with climatic and environmental indices (maximum air temperature, sea surface temperature, wind speed and chlorophyll a). Results revealed that, between 2004 and 2010, coastal regions of mainland Tanzania inhabited by approximately 21% of the total population accounted for approximately 50% of the cholera cases and 40% of the total mortality. Significant co-variations were found between seasonally adjusted cholera cases and coastal ocean chlorophyll a and, to some degree, sea surface temperature, the outbreaks lagging behind by one to four months. Cholera cases in Dar es Salaam were also weakly related to the Indian Ocean Dipole Mode Index, lagging by five months, suggesting that it may be possible to predict cholera outbreaks for Dar es Salaam this period ahead. The results also suggest that the severity of cholera in coastal regions can be predicted by ocean conditions and that longer-term environmental and climate parameters may be used to predict cholera outbreaks along the coastal regions.

Local participation, especially in natural resource management, has been promoted as a key strategy in the quest for sustainable development. Community-based Natural Resource Management (CBNRM) is an approach that has generally been promoted as an institution that genuinely includes and empowers ‘local people' in natural resource use and management. This paper examines how local participation in conservation projects works in practice by drawing on concepts from institutional and actor-oriented theories and applying a case study approach to examine community-based mangrove management at Jozani-Pete, Zanzibar. Here CBNRM became embedded within a conservation agenda that resulted in conflict, resistance, frustration and uncertainty amongst community members. The paper offers insight into how exogenously initiated CBNRM projects have difficulty gaining traction unless they both address existing power relations and deliver on promises of material benefits. If they fail to do so the experience of the Jozani-Pete case study suggests that CBNRM may work to further marginalize already marginalized people.