Freshwater habitats are the most threatened on the planet, facing impacts from overfishing, habitat degradation, and the introduction of non-native invasive species. This thesis focuses on the importance of freshwater ecosystems for fisheries and aquaculture, and the threats that are currently facing the unique biodiversity of these systems. In Chapter 1 I discuss the importance of freshwater ecosystems, and review the key threats faced by freshwater fish species. I focus on the Nile Tilapia (Oreochromis niloticus), a species that has been widely introduced to non-native habitats for capture fisheries improvement, and following escapes from aquaculture ponds. I describe how this invasive species can impact on unique genetic resources of native species through hybridization. In Chapter 2 I report an investigation of hybridization between Oreochromis niloticus and newly discovered populations of an indigenous species, Oreochromis korogwe, that were first reported from southern Tanzania in 2013. Using genetic (microsatellite) evidence, I show that hybridization is taking place in all three locations in southern Tanzania where O. korogwe is known to occur (Lakes Nambawala, Rutamba and Mitupa). I also show that the O. korogwe in the southern Tanzania are genetically and morphologically different to populations known from northern Tanzania. I conclude that these newly discovered southern Tanzanian populations are already being threatened by hybridization with an invasive species that threatens their unique and irreplaceable genetic resources. In Chapter 3 I highlight the research requirements needed to further understand the extent of hybridization between indigenous and non-native fish species in Africa, and to inform future conservation and management plans.
|Date of Award||6 Nov 2018|
- The University of Bristol
|Supervisor||Martin J Genner (Supervisor)|