Section 6.2: Radio Tracking of African Cichlids in a Large Floodplain River: Challenges and Results from the Zambezi River in Namibia
Eva B. Thorstad, Clinton J. Hay, Finn Økland, and Tor F. Næsje
Namibia is one of the driest countries in the world, and people strongly depend on the availability of open water bodies in the northern parts of the country (Cuvelai River System, Kavango River and Zambezi/Chobe River System) for fish to eat and water supplies (Mendelsohn et al. 2002). All perennial rivers are shared with neighboring countries. The Zambezi River is the fourth largest river system in Africa, flowing through Zambia, Angola, Namibia, and Zimbabwe, before emptying into the Indian Ocean in Mozambique. This drainage forms the 120 km long border between Namibia and Zambia, where the present study was performed. More than 70 fish species have been recorded in this river section (Hay et al. 2002).
The large cichlids (Cichlidae) are valuable species in small scale commercial and subsistence fisheries in the upper Zambezi and are also popular among recreational anglers. However, reports of reduced catches are a major concern for the Namibia management authorities (Anonymous 1995). To be able to develop spatial management strategies, information on seasonal fish movement and habitat use is fundamental. A series of radio telemetry studies were therefore performed in the Namibian section of the upper Zambezi River, to achieve information on movements and habitat use for a number of fish species (Thorstad et al. 2001, 2004, 2005; Økland et al. 2005, 2007).
Performing radio telemetry studies in all water systems provides a number of challenges. However, the size and complexity of a floodplain river like the Zambezi River, the general lack of knowledge on the fish resources, and the undeveloped, remoteness of the study area make studies even more challenging. The aim of this Section is therefore threefold: 1) present results on behavior and habitat use of one of the most important cichlids in the upper Zambezi River, the greenhead tilapia Oreochromis macrochir, 2) compare the results with previous studies on the cichlids nembwe Serranochromis robustus, three spotted tilapia Oreochromis andersonii and pink bream Sargochromis giardi (Thorstad et al. 2001, 2005; Økland et al. 2007), and 3) discuss some of the challenges with performing telemetry studies in such a large and complex floodplain river system.