Suchergebnisse

AbstractFor sub‐Saharan African countries with few evident opportunities to diversify export earnings away from primary commodities, tourism has emerged as an option to contribute to economic growth. This study uses input–output analysis to estimate the economic impact of tourism and assesses its potential contribution for the Tanzanian economy. The results show that tourism has a significant impact on output and incomes, especially taking into account the strong inter‐sector linkage effects, although this has not been translated into corresponding employment gains. The tourism sector also contributes to tax revenue and foreign exchange earnings. Overall, tourism is shown to make a significant economic contribution. Copyright © 2003 John Wiley & Sons, Ltd.

Species translocation leads to disease emergence in native species of considerable economic importance. Generalist parasites are more likely to be transported, become established and infect new hosts, thus their risk needs to be evaluated. Freshwater systems are particularly at risk from parasite introductions due to the frequency of fish movements, lack of international legislative controls for non-listed pathogens and inherent difficulties with monitoring disease introductions in wild fish populations. Here we used one of the world's most invasive freshwater fish, the topmouth gudgeon, Pseudorasbora parva, to demonstrate the risk posed by an emergent generalist parasite, Sphaerothecum destruens. Pseudorasbora parva has spread to 32 countries from its native range in China through the aquaculture trade and has introduced S. destruens to at least five of these. We systematically investigated the spread of S. destruens through Great Britain and its establishment in native fish communities through a combination of phylogenetic studies of the host and parasite and a novel environmental DNA detection assay. Molecular approaches confirmed that S. destruens is present in 50% of the P. parva communities tested and was also detected in resident native fish communities but in the absence of notable histopathological changes. We identified specific P. parva haplotypes associated with S. destruens and evaluated the risk of disease emergence from this cryptic fish parasite. We provide a framework that can be applied to any aquatic pathogen to enhance detection and help mitigate future disease risks in wild fish populations.