Controversy surrounds the global dissemination of Nile tilapia (Oreochromis niloticus), reflecting tension between possible negative impacts on native fish production relative to the socio-economic benefits of Nile tilapia aquaculture. The objective of this Doctoral Dissertation Enhancement Project is to inform this global debate by quantifying the impact of Nile tilapia introduction on a native Oreochromis fishery. The central hypothesis of this case study on the Kafue River, Zambia, is that introduced O. niloticus out-compete native O. andersonii males for mates, driving directional hybridization which may alter fisheries production in the long term. Field sampling for genetic detection of hybridization coupled with competition experiments will test this hypothesis by quantitatively parameterizing models which will estimate the differences in somatic and population growth rates between parental and hybrid types.
By developing collaborative research with foreign partners, such as University of Zambia lecturer Dr. Cyprian Katongo and Zambian master's students, this project contributes to the underlying doctoral dissertation through advising, planning and experimental execution. This will be the first research to experimentally investigate ecological linkages between Nile tilapia invasion in Africa and sustainable fisheries production, thus improving the intellectual merit of the dissertation. Moreover, field sampling will extend the long term fishery dataset for the Kafue, which is essential to developing this river as a case study.
Broader impacts derive from strong collaborative partnerships with the University of Zambia, Zambian Department of Fisheries, and The World Fish Center. These partnerships ensure research will inform decisions about the introduction of Nile tilapia relative to the sustainable development of aquatic resources in Zambia and worldwide. This proposal serves as the seed for a larger collaboration and further NSF support by informing the specific design of experiments in a future proposal. Further, it provides a US graduate student the opportunity to engage in international collaborative research.
This award is being funded by NSF's Office of International Science and Engineering.
Nile tilapia (Oreochromis niloticus) is an extremely popular food fish and is one of the most farmed fish in the world. There is controversy surrounding the global spread of Nile tilapia however, because of the potential for negative environmental impacts of Nile tilapia introduction on native fisheries relative to the socio-economic benefits of farming Nile tilapia. This projectâ€™s objective was to use field sampling and experiments focusing on a case study of Nile tilapia introduction in the Kafue River, Zambia, to help resolve this dilemma, We collected 266 total individual Oreochromis spp. from the Kafue River in close collaboration with the Zambian Department of Fisheries. These collections extend the extensive long-term data set on the Kafue River, uniquely contributing to detailed analysis of the historical trends in fishing effort, total harvest and floodplain regime critical to the sustainable economic development of Zambia. Genetic analyses of the collected specimens established that the introduced Nile tilapia is mating with the native 3-spot tilapia (O. andersonii) and producing hybrid offspring. To experimentally test the potential consequences of this hybridization for long-term fisheries sustainability, we have established stable experimental populations of both Nile tilapia and 3-spot tilapia at our facilities at the University of Notre Dame. The collaborations with Zambian partner institutions established with this project support the next generation of globally engaged and socially aware American scientists solving a multi-faceted real world problem; the tradeoff between the benefits of using introduced species in commerce and the potential productivity and other benefits of native fisheries. Results from these studies serve to support decision making around the world and in the United States where tilapia farming is being developed, and improve the efficiency of foreign aid to countries looking to fish farming for economic development and trade with the United States.