Genetic diversity and gene flow among the giant mud crabs (Scylla serrata) in anthropogenic-polluted mangroves of mainland Tanzania: Implications for conservation

The rapidly growing coastal population in East Africa has led to increased exploitation of shellfish and incidences of habitat degradation. This study analysed fragments (554 base pairs) of the cytochrome oxidase subunit I gene and eight microsatellite loci from 199 DNA extracts of giant mud crabs collected from anthropogenic-polluted mangroves of mainland Tanzania in order to describe the patterns of genetic diversity and gene flow. Correlation and regression analysis showed that the measured indices of genetic diversity and connectivity are not associated with the reported levels of trace metal pollution. Both mitochondrial and microsatellite DNA did not show significant differentiation, suggesting that gene flow is high enough to counteract the effect of pollution on genetic diversity and differentiation. Apart from that, microsatellite DNA showed that mangroves in major coastal cities and mangroves affected by salt farming activities are associated with low effective population size compared to mangroves in protected areas. Since the human coastal population is expanding rapidly, measures should be taken to strengthen the existing marine parks and reserves and to promote sustainable use of coastal resources.