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Space Use and Habitat Utilisation of Tigerfish and the Two Cichlid Species Nembwe and Threespot Tilapia in the Upper Zambezi River

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Space Use and Habitat Utilisation of Tigerfish and the Two Cichlid Species Nembwe and Threespot Tilapia in the Upper Zambezi River SpaceSpace useuse andand habitathabitat utilisationutilisation ofof tigerfishtigerfish andand thethe twotwo cichlidcichlid speciesspecies nembwenembwe andand threespotthreespot tilapiatilapia inin thethe UpperUpper ZambeziZambezi RiverRiver Implications for fisheries management NINA Project Report no. 24 Directorate Resource Management Norwegian Institute for Nature Research Ministry of Fisheries and Marine Resources Tungasletta 2 Private Bag 13 355 Windhoek NO-7485 Trondheim Namibia Norway NINA Norwegian Institute for Nature Research Space use and habitat utilisation of tigerfish and the two cichlid species nembwe and threespot tilapia in the Upper Zambezi River Implications for fisheries management Eva B. Thorstad* , Clinton J. Hay**, Tor F. Næsje*, Ben Chanda*** & Finn Økland* * Norwegian Institute for Nature Research (NINA), Tungasletta 2, NO-7485 Trondheim, Norway. ** Ministry of Fisheries and Marine Resources, Private Bag 2116, Mariental, Namibia. *** Ministry of Agriculture and Co-operatives, Department of Research and Specialised Ser- vices, P.O. Box 350100, Chilanga, Zambia. nina Project Report 24 Thorstad, E.B., Hay, C.J., Næsje, T.F., Chanda, B. & Økland, Norwegian Institute for Nature Research F. 2003. Space use and habitat utilisation of tigerfish and the (NINA) issue the following publications: two cichlid species nembwe and threespot tilapia in the Upper Zambezi River. Implications for fisheries management. - NINA NINA Project Report Project Report 24. 23 pp. This series presents the results of the institutes' projects when the results are to be made available in English. The Trondheim, October 2003 series may include reports on original research, literature reviews, analysis of particular problems or subjects, etc. The ISSN 1502-6779 number of copies printed will depend on demand. ISBN 82-426-1417-2 In addition to this report series published in English, NINA publish the following series in Norwegian: Management area: Fish, humans, sustainable utilisation NINA Fagrapport (Scientific Reports) This series present the results of NINAs own research work, Copyright©: overviews of problems, existing knowledge within a topic, Norwegian Institute for Nature Research literature reviews and material gathered from outside sources. The reports are issued as an alternative or a sup- This publication was made possible through support provided plement to international publication when timing, the nature by the US Agency for Development (USAID) Namibia Mission of the material or the sector targeted, call for it. and the World Wildlife Fund (WWF) under the terms of the Co- operataive Agreement No. 690-A-00-99-00227-00. The views NINA Oppdragsmelding (Assignment Report) expressed in this document are the views of the editor or con- This is the minimum report supplied by NINA when external tributors and are not necessarily those of USAID or WWF. research or investigative assignments have been completed. The numbers of copies are limited. NINA Temahefte (Topic) These series present special topics. They are targeted at the general public or specific groups in the community, e.g. the agricultural sector, environmental departments, tourism and outdoor recreation, organizations etc. It is therefore more popular in its presentation form, with more illustrations than The report can be quoted with references to the source. the previously mentioned series. Editor: Tor F. Næsje Most of the publications mentioned above are in Norwegian, but will also have an English abstract and legends of figures Design og layout: Synnøve Vanvik and tables in English. Stock: 400 NINA Fact Sheet (Fakta-ark) These double-pages sheets give (in Norwegian) a popular Adress to contact: summary of other publications to make the results of NINAs Eva B. Thorstad work available to the general public (the media, societies NINA and organizations, various levels of nature management, Tungasletta 2 politicians and interested individuals). NO-7485 Trondheim Norway NINAs staffs also publish their research results in inter- Email: [email protected] national scientific journals, popular scientific periodicals, and Tel.: +47 73 80 14 00 newspapers. Fax.: +47 73 80 14 01 http://www.nina.no Accessibility: Open Contracting sponsors: World Wildlife Fund (WWF) Project no.: 13532 Ministry of Fisheries and Marine Resources (MFMR) Norwegian Institute for Nature Research (NINA) Signature of responsible person: 2 nina Project Report 24 Abstract tigerfish as the species with the most extensive movements and threespot tilapia as the intermedi- Thorstad, E.B., Hay, C.J., Næsje, T.F., Chanda, B. ate. Average distance moved between tracking & Økland, F. 2003. Space use and habitat utilisa- surveys was 16 times longer for tigerfish (1447 m) tion of tigerfish and the two cichlid species than for nembwe (93 m), and 4 times longer for nembwe and threespot tilapia in the Upper Zam- threespot tilapia (391 m) than for nembwe. Mean bezi River. Implications for fisheries management. length of the river stretch used was 14 times longer - NINA Project Report 24. 23 pp. for tigerfish (18.8 km) than for nembwe (1.3 km), and 4 times longer for threespot tilapia (5.4 km) Background and objectives than for nembwe. A successful management of floodplain fisheries, such as in the Caprivi Region in Namibia, depends Most riverine cichlid species are in the literature on a good understanding of the fish migrations and regarded as having a highly resident life style. Al- habitat preferences in these complex and variable though systematic migratory patterns were not ecosystems. Therefore, studies of the movements demonstrated in this study, the cichlids were to a and habitat utilisation of radio tagged fish in the relatively large extent moving around, especially Upper Zambezi River were initiated by the Nami- the threespot tilapia. Thus, the large riverine cich- bian Ministry of Fisheries and Marine Resources in lids may not be as highly resident as previously 1999. The movements and habitat utilisation of suggested. tigerfish (Hydrocynus vittatus Castelnau, 1861), The tigerfish showed a variable movement pattern, nembwe (Serranochromis robustus Günther, 1864) with approximately half of the fish staying within and threespot tilapia (Oreochromis andersonii defined home ranges, only performing movements Castelnau, 1861) were studied in 2000/2001, and less than 1,000 m between tracking surveys. The the species specific results have been presented in remaining tigerfish were resident for periods, but three previous reports. The three species were moved over long distances (on average 18,784 m) studied in the same area of the river during the to new areas between the residency periods. same period, and the results are therefore compa- However, home range size (the area with 95% rable. probability of localisation of the fish) was not larger The objectives of this report are to: for tigerfish than for the two other species, even 1) summarise and compare the recorded move- though the movements were more extensive. ments and habitat utilisation of tigerfish, Approximately half of the individuals of all three nembwe and threespot tilapia, and species moved to temporary water covered areas 2) outline the implications of fish movements and during rising and high water levels. The tigerfish habitat utilisation for fisheries management. differed from the two other species in the utilisation of temporary water covered areas, as they were Comparison of movements and habitat utilisa- recorded in temporary water covered areas to a tion among tigerfish, nembwe and threespot lesser extent during rising water level. However, tilapia during high water level, the utilisation of temporary Movements and habitat utilisation were recorded water covered areas was similar for the three spe- for 15 tigerfish (body lengths 30-54 cm), 13 cies. nembwe (body lengths 32-40 cm) and 6 threespot tilapia (body lengths 25-50 cm). Fish were caught The three species seemed more similar in their and radio tagged during 6 November - 24 Decem- habitat utilisation than in their movement patterns. ber 2000, and they were tracked until 18 May All species were much of the time associated with 2001. The tigerfish were positioned on average the main river, and stayed in relatively deep, open every 4.1 day, the nembwe every 3.7 day and the water bodies at some distance from shore. How- threespot tilapia every 4.4 day. ever, adults of these species are apparently not habitat specialists, and the fish were recorded in a The three species differed in their movement pat- wide range of habitats. Variation in habitat utilisa- terns, with nembwe as the most stationary species, 3 nina Project Report 24 tion was relatively large both within and among caught in gillnets will also depend on the daily individuals. The results indicate that adults of all movement patterns, the local activity patterns, and three species were more associated with vegeta- if the gill net fishery targets certain species. tion than previously assumed, although tigerfish were to a lesser extent associated with vegetation Key words: Hydrocynus vittatus - Serranochromis than threespot tilapia and nembwe. robustus - Oreochromis andersonii - tigerfish - nembwe - threespot tilapia - radio telemetry - Implications for fisheries management movement - habitat - management. Coordination of local and regional management regulations is important for the management of Eva B. Thorstad , Tor F. Næsje and Finn Økland, tigerfish, nembwe and threespot tilapia, to maintain Norwegian Institute for Nature
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