GLOBES Research Summary
Andy Deines
Email: adeines@nd.edu
Department: Biological Sciences
Advisor: David Lodge
Interaction and Impact of Nile Tilapia on the Kafue Watershed in Zambia
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The freshwater fish, Nile tilapia (Oreochromis niloticus) has been introduced worldwide as an important protein source for developing regions. The same robust qualities that make it a successful species in aquaculture, however also make it highly invasive when it escapes to open water. Experts are unanimous that introductions of Nile tilapia should be avoided (Canonico et al 2005) even though the interactions and effects of tilapia on native ecosystems are rarely more than casually noted (Pullin et al 1997). There appear to be no quantitative analyses exploring the mechanisms of invasion and the larger ecosystem effects of tilapia introduction (Canonico et al 2005). Due to the certainty of economic benefits from tilapia aquaculture compared to the high uncertainty of environmental impacts upon escape, O. niloticus remains the fish of choice for development activities (ADB 2005, Josupeit 2006), and for this reason the Nile tilapia was introduced to Zambia for fish farming in 1982 (Audenaerde 1994).
The presence of feral Nile tilapia (Oreochromis niloticus) in the Kafue River, Zambia (Figure 1) was confirmed in 1994 (Schwanck 1995). Based on morphology, putative hybrids of O. niloticus and the native tilapias, O. andersonii and Tilapia rendalli where observed as early as 1989 (Nyimbili 2006). As has occurred in other regions of the world, it is of concern that the introduction of Nile tilapia may cause dramatic changes in the fish community (Canonico, Arthington et al. 2005) by hybridization and other ecological mechanisms potentially effecting an important fishery resource in Zambia’s developing economy.
The core of this research agenda asks how the Nile Tilapia might impact the total output and sustainability of the Kafue Flats fishery. Two ecological mechanisms of impact are most often suggested by the literature: 1) Competition for spawning sites and other habitat, and 2) hybridization with native tilapia species. To complicate matters, the river’s flood regime may distribute species interactions across wide scales of time and space, and predation by the artisanal fishery at these various scales cannot be ignored. The ecological questions arising from these issues can best be answered in three ways: first, by constructing and analyzing a historical dataset of changes in the fish community, the fishery, and the flood regime; second, by surveying the spatial extent and genetic introgression and hybridization in the Kafue River; and third, by conducting experimental pond studies to determine possible impacts of competition and hybridization.
The impacts of the Nile tilapia however may have broader reaching associations than just those of ecological studies, particularly because it is a potentially important food source. Total fishery output may also respond to managerial and political fishery strategies as well as market driven reactions to this introduced food species, both of which will dictate overall fishing effort and thus, production. Therefore, an interdisciplinary team of researchers focused on the particular aspects of ecology, genetics, policy, and economics are/will be analyzing the impacts of Nile tilapia introductions to the Kafue River in collaboration with the Zambian Department of Fisheries, the University of Zambia, The WorldFish Center and other partners.
Audenaerde, D. F. E. T. v. d. (1994). Introduction of aquatic species into Zambian waters, and their importance for aquaculture and fisheries. Harare, Zimbabwe, Aquaculture for Local Community Development Programme (ALCOM): 33.
Canonico, G. C., A. Arthington, et al. (2005). "The effects of introduced tilapias on native biodiversity." AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS 15: 463-483.
Nyimbili, B. (2006). An evaluation of fish population changes in the Kafue Flats floodplain fishery of Zambia from 1980 to 2005. Department of Biology. Bergen, Norway, University of Bergen: 66.
Schwanck, E. J. (1995). "The introduced Oreochromis niloticus is spreading on the kafue floodplain, Zambia." Hydrobiologia 315: 143-147.
Research Publications and Presentations
Deines, AM, Klco, B, Lodge, DM. Ecological mechanisms and impact of tilapia: review of empirical evidence. Managing Alien Species for Sustainable Development of Aquaculture and Fisheries (MALIAF). Florence, Italy. Nov 5-7, 2008. Oral Presentation.
Deines, AM., Bee, CA., Katongo, C., Malasha, I., Mudenda HG. (2008, March) Nile Tilapia Invasion on the Kafue River, Zambia: An IGERT-GLOBES Project. Minnesota Futures and IGERT Symposium: Predicting Invasive Potential of Exotic Species. University of Minnesota. Minneapolis, MN, USA. Poster
Deines, AM. (2008, April 9-11) Tilapia for Aquaculture: Impacts and Uncertainty. Workshop on Preventing Biological Invasions: Best Practices in Pre-Import Risk Screening for Species of Live Animals in International Trade. University of Notre Dame, IN, USA. April 9-11, 2008. Poster