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Home , Lake Nabugabo, Lake Victoria

Nabugabo and their current conservation status

Item Type book_section

Authors Namulemo, G.; Mbabazi, D.

Publisher Wetlands Inspection Division

Download date 28/09/2021 02:44:36

Link to Item http://hdl.handle.net/1834/35582 A compilation of

Scientific Information on

Nabugabo Ramsar Site,

Proceedings ofthe Scientific Conference held at Nabugabo in January, 2001

.;n'. ~ .~~.: ~"ST~ Tl1E REPUBLIC OF UGANDA (0

Edited by:

Busulwa H., P. G. Mafabi and L. M. Ndawula

2005

The Nabugabo Ramsar Site NABUGABOLAKESANDTHEIRCURRENT As in the c; CONSERVATION STATUS several tila accompanit Namulemo Gertrude and Dismas Mbabazi, A survey Cc National Agricultural Research Organization, Resources Research Institute, P. O. Box 343, Jinja. species that 0. variabil, Abstract Clar;as gar 1993). How species diversity in Nabugabo, Uganda, has declined following establishment of Lake Nabug the introduced fish species in the lake. Most of the native fish species have disappeared and of the nativ( the lake is now dominated by the introduced perch, niloticus and the Nile Ohwayo,19 niloticus. The dominant native fish species include aji-ofischeri, Schilbe intermedius, Rastrineobola argentea and Brycinus sadleri. Some of the native fish species that have disappeared from were reported to occur in lakes Kayugi and Kayanja, Loss of bioe which are adjacent to Lake Nabugabo but separated from it by extensive papyrus swamps. The directed at t Nabugabo lakes are satellite water bodies in the basin, which is known to have types of bio experienc~d fish species changes due to the introduction ofthe Lates niloticus during recognized: the 1960s. The Nabugabo lakes comprising of Lake Nabugabo main, and the smaller lakes and refugia , Kayanja and Kayugi were investigated between 2000 and 2002 with experimental gillnetting to evaluate the potential of these lakes in conservation offish species diversity. Results show In this study, that some native fish species especially , and investigated 1 and the Prognathochromis venator that have disappeared from Lake potential on Nabugabo still occur in Lakes Kayanja and Kayugi. Inshore habitats with macrophyte cover were also found to be important habitats for the endangered native fish species in the Nabugabo Study area lakes. These lakes and inshore habitats need to be protected to conserve the endangered native fish species and to reduce further decline in fish species diversity. Three lakes \! Keywords: Conservation, fish species, refugia on pg. 5). Lak swamp, whicl Introduction length offive] shore, the lak Fish species diversity and water quality in the East are now main inflows critically threatened by human impacts (Kaufman, 1993). The Lake Victoria The outflow a system was the first to show collapsing fisheries, wholesale loss offish species bar that forms diversity and lake-wide environmental degradation. Decline in fish species sites, represen diversity has been attributed to over-fishing, the introduction of non-native "Dead duck" 1 species, deleterious land use practices and pollution from various sources. Over 50% of the endemic disappeared from Lake Victoria between Lake Kayugi r 1980 and 1986 and many are presumed extinct (Kaufman, 1992). Predation A thick papyn by the introduced Nile perch Lates niloticus is reported to have been a major surrounds the. contribution to the mass of the native fish species (Ogutu-Ohwayo, 1993). Similar changes have occurred with the introduction ofNile perch into Lake Kayanja other lakes in the region e.g. Lakes Kyoga and Nabugabo. 1.2 km2 with a 76 The Nabugabo Ramsar Site The Nabugabo Ram ~NT As in the case of lakes Victoria and Kyoga, the introduction of Nile perch and several tilapiines into Lake Nabugabo in 1960 (Ogutu-Ohwayo, 1993) was accompanied by disappearance ofmany ofthe native fish species from the lake. A survey carried out in Lake Nabugabo in 1991 and 1992 revealed that of the O. Box 343, species that formed the basis ofthe pre-perch commercial , (0. esculentus, 0. variabilis, and Bagrus docmak) were absent while Schilbe intermedius, Clarias gariepinus and Protopterus aethiopicus were rare (Ogutu-Ohwayo, 1993). However, lakes Kayanja, Kayugi and Manywa, which are adjacent to Lake Nabugabo but separated from it by extensive swamps, still contain some ablishment of ;appeared and of the native fish species that have disappeared from Lake Nabugabo (Ogutu­ Ie Ohwayo, 1993). ,cheri, Schilbe ,h species that Loss of biodiversity in the Lake Victoria basin has led to a series of studies and Kayanja, ; swamps. The directed at the identification of faunal refugia (Kaufman, 1993). Two major mown to have types of biodiversity refugia in lakes harbouring introduced Nile perc~ are iloticus during recognized: refugia outside the lakes (satellite lakes and associated wetlflnds) smaller lakes and refugia within the lakes (wetlands and rocky shores, Chapman in press.). t1tal gillnetting In this study, a cluster of water bodies referred to as the Nabugabo lakes was Results show Jmis variabilis investigated between 2000 and 2002 with a major objective of determining the red from Lake potential ofNabugabo lakes in conservation offish species diversity. :rophyte cover I the Nabugabo Study area angered native Three lakes were sampled namely, Nabugabo, Kayanja, and Kayugi (Figure 1 on pg. 5). Lake Nabugabo is a small shallow open lake lying within an extensive swamp, which fills a former bay on the western shore of Lake Victoria. It has a length offive miles and a maximum width ofthree miles. Except for the western shore, the lake margin is swamp. It has a maximum depth of fifteen feet. The main inflows to Lake Nabugabo are River Juma and the Lwamunda swamp. akes are now ,ake Victoria The outflow ofthe lake is into Lake Victoria and is by seepage through the sand ffish species bar that forms the eastern barrier between the two lakes. In Lake Nabugabo, five sites, representing different habitat types, were sampled namely River mouth, fish species "Dead duck" bay, Lubira, Campsite and Open water station. )f non-native lOus sources. 2 Lake Kayugi has a maximum depth ofabout 3.0 m and an area ofabout 0.1 km • aria between A thick papyrus swamp that is connected to Lake Nabugabo via River Juma 2). Predation surrounds the lake and is fed by River Kagona from the northwest. been a major ~utu-Ohwayo, Lake Kayanja is not connected to Lake Nabugabo. It has a surface area ofabout :ile perch into 1.2 km2 with a maximum depth ofabout 3.0 m. Apart from the eastern shoreline,

Jgabo Ramsar Site The Nabugabo Ramsar Site 77 the lake is surrounded by an extensive Loudentia phragmitoides dominated Table 1. Fish spel swamp. The swamp around this lake is fed by rivers Nsonzemu and Kikoma + = enco from the North-west and drains via River Kanwa eastwards, into Nakiga Bay ofLake Victoria Fish species

Materials and methods Native species ! i '.~-,, . Afromastacemb '" Fish specimens were obtained from experimental gillnets set at various sites kersten, within the different lakes. Three graded fleets of gillnets, each consisting of Barbus magdall nets of mesh size 25.4 mm to 305 mm stretched mesh at 12.7 mm intervals Brycinus sadler, it were used. The first fleet was set close to the shoreline, (inshore) the second was set approximately 20 m from the shoreline (midshore) and the third was Clarias garieph 1m, set 200 m from the second fleet (offshore). All the fleets were set parallel to the Clarias lioceph( Iii ~I shoreline. In Lake Kayugi only two fleets were used (inshore and open water) Gnathonemus 10 ','• I!: due to the small size of the lake. The nets were set at dusk, left overnight and Gnathonemus vii retrieved the following morning. On retrieval, fish were sorted into taxonomic Hap!ochromines groups to species level whenever possible and the numb~r and weight ofeach Marcusenills gra taxa in each mesh size ofnet recorded. Relative abundance ofeach species was Oreochromis esc

calculated as a percentage offish captured in each net at each site. Petrocepha!us CG Protopterus aeth Results Schitbe intermed, Synodontis afrofi, Overall 18 fish taxa were recorded from the Nabugabo lakes as shown in Table 1. They included , Brycinus sadleri, Barbus kersternii, Introduced spec Barbus magdalenae, Gnathonemus longibarbis, Lates niloticus, Marcusenius grahami, Tilapia rendalii, , Oreochromis esculentus, Lates niloticus Oreochromis niloticus,Protopterus aethiopicus,Schilbe intermedius,Synodontis Oreochromis !eu( afrojischeri and Tilapia zillii. The haplochromines included Astatoreochromis Oreochromis nita alluaudi, Astatotilapia velifer, Astatotilapia nubila, Gaurochromis simpsoni, Tilapia rendalii Paralabidochromis beadlei and Prognathochromis venator. Tilapia zillii Total

Overall 13 fish ta haplochromines, niloticus, M graJ S. intermedius, S bay stations had and Campsite (11 station, 10 fish B.sadleri, 1. nilot

The Nabugabo Ramsar Site 78 The Nabugabo Ramsar 'des dominated Table 1. Fish species composition in Lakes Nabugabo, Kayanja and Kayugi from 2000 to 2002. III and Kikoma + = encountered, - = not encountered. Lto Nakiga Bay Fish species Nabugabo Kayanja Kayugi

Native species Afromastacembelusfrenatus + - - at various sites Barbus kersternii + + + h consisting of Bm-bus magdalenae + - - 7 mm intervals Brycinus sadleri + - + )re) the second Clarias gariepinus - + + d the third was Clarias liocephalus - + - t parallel to the nd open water) Gnathonemus longibarbis + - - t overnight and Gnathonemus victoriae + + + into taxonomic Haplochromines + + + weight of each Marcusenius grahami ". + - + lch species was Oreochromis esculentus - + + teo Petrocephalus catastoma + + + Protopterus aethiopicus + + + Schilbe intermedius + - - + - - :s as shown in . :1" ..bus kersternii, " ~ s, Marcusenius Lates niloticus + - - mis esculentus, Oreochromis leucostictus + + + lius,Synodontis tatoreochromis Oreochromis niloticus + - - 'Om is simpsoni, Tilapia rendalii + - - Tilapia zillii + + + Total 17 10 11

Overall 13 fish taxa were recorded from L. Nabugabo (Table 2). They included haplochromines, B. sadleri, B. kersternii, B. magdalenae, G. longibarbis, L. niloticus, M grahami, 0. rendalii, 0. leucostictus, 0. niloticus, P aethiopicus, S. intermedius, S. afrofischeri and T zillii. River Juma mouth and Dead duck bay stations had the highest number of fish species (12) followed by Lubira and Campsite (10) and lastly Open water station (7). From Dead duck bay station, 10 fish taxa were recorded and they included haplochromines, B.sadleri, L. niloticus, T. rendalii, 0. leucostictus, 0. niloticus, S. intermedius,

lbugabo Ramsar Site The Nabugabo Ramsar Site 79 rr I~, I·'

I" S. afrofischeri and T zillii. From River Juma mouth, 10 fish taxa were recorded 10 fish taxa 1 i namely haplochromines, B. sadleri, Barbus kerstern, Barbus magdalenae, B. kersterni, ( Gnathonemus longibarbis, L. niloticus. T rendalii, 0. leucostictus, 0. escu!entus, 0. I niloticus, S. afrofischeri and T zillii. From the campsite 10, fish taxa recorded varied with di: included haplochromines, B. sadleri, L. niloticus, M grahami, T rendalii, O. number of fish I· I::f' leucostictus, 0. niloticus, S. intermedius and T zillii. From Lubira, 6 fish taxa The haplochror recorded included haplochromines, B. sadleri, L. niloticus, 0. niloticus, and S. venator. intermedius. Seven fish taxa were recorded from the open water station namely haplochromines, P aethiopicus, L. niloticus and S. intermedius. Four species Table 3. Composil distance f of haplochromine were recorded from Lake Nabugabo and they

1 were A. velifer, G. simpsoni, P beadlei and A. alluaudi. In Lake Nabugabo, Fish species I:.1. ' •.• distribution offish varied with species as shown in Table 3. A. mastercembelus, B. magdalenae and P catastoma were recorded from the shoreline, T zillii, Afromastacembe haplochromines, and B. kersternii were most dominant in the inshore fleet. S. Barbus kersterni. Barbus magdalef " afrofischeri, S. intermedius and L.niloticus were recorded from all stations but were most dominant in the offshore habitat. Brycinus sadleri Gnathonemus Ion Table 2. 'Fish species occurrence at various sites sampled in Lake .!'Iabugabo between 2000 and J 2002 + = encountered, - = not encountered. Gnathonemus vic, :~:! Haplochromines Fish species Campsite Open Duck Lubira R. Juma Lates niloticus l,' lI water bay Marcusenius grah Afromastacembelusfrenatus -- + + - Oreochromis leuc( Ii Barbus kersternii + - - - + Oreochromis nilot, Barbus magdalenae - + Petrocephalus cat, Bryc!nus sadleri + + + + + Protopterus aethia, Gnathonemus longibarbis - - + + + Schilbe intermediu. Gnathonemus victoriae - - - + - Synodontis afrofisc Haplochromines + + + + + Tilapia rendalii Lates niloticus + + + + + Tilapia zillii Marcusenius grahami - + - - - Total Oreochromis leucostictus + - + - + Oreochromis niloticus - + + + + FromLake Kayugi, Petrocephalus catastoma - - + + - B. sadleri, B. kerstE Protopterus aethiopicus - + - - - P catastoma, 0. lei Schilbe intermedius + - + + + number of fish spe Synodontis afrofischeri + - + + + haplochromine cid Tilapia rendalii + - + - + and P venator. Tilapia zillii + + + - + Total 10 7 12 10 12

80 The Nabugabo Ramsar Site The Nabugabo Ramsar Sit lxa were recorded 10 fish taxa were recorded from Lake Kayanja namely haplochromines, bus magdalenae, B. kersterni, C. gariepinus, C. liocephalus, G. victoriae, M grahami, 0. leucostictus, 0. esculentus,o. leucostictus, P aethiopicus and T. zillii. Fish species distribution fish taxa recorded varied with distance from the shoreline as shown in Table 4. Overall the '11i, T. rendalii, 0. number of fish species decreased with increasing distance from the shoreline. :"ubira, 6 fish taxa The haplochromine species included A. alluaudi, A. nubila, A. velifer and P ). niloticus, and S. venator. Iter station namely Table 3. Composition, diversity and percentage contribution of various fish species in relation to dius. Four species distance from the shoreline in Lake Nabugabo from 2000 to 2002 bugabo and they 1 Lake Nabugabo, Fish species Inshore Midshore Offshore t. mastercembelus, Afromastacembelus frenatus 0.1 0 0 shoreline, T. zillii, Barbus kersternii 0.5 0.4 0.4 he inshore fleet. S. om all stations but Barbus magdalenae 0.1 0 0 Brycinus sadleri 19.6 25.5 0 Gnathonemus longibarbis 0 0.1 0, :abo between 2000 and Gnathonemus victoriae 0 0.1 5.5 Haplochromines 46.1 21.7 25.7 ,ubira R.Juma Lates niloticus 10.0 12.1 16.0 Marcusenius grahami 0 0 0.1 + - Oreochromis leucostictus 0.7 0.4 0.4 - + Oreochromis niloticus 7.4 19.0 3.7 + Petrocephalus catastoma 0.1 0 0 + + Protopterus aethiopicus 0 0 0 + + Schilbe intermedius 7.5 14.3 39.2 + - Synodontis afrofischeri 7.1 6.0 7.9 + + Tilapia rendalii 0.2 0.1 0.4 + + Tilapia zillii 0.8 0.30 0.8 - - Total 13 12 11 - + + + From Lake Kayugi, 11 fish taxa were recorded and they includedhaplochromines, + - B. sadleri, B. kersterni, C. gariepinus, G. victoriae, M grahami, 0. esculentus, - - P catastoma, 0. leucostictus, and P aethiopicus. Inshore habitats had a higher + + number of fish species than the open watcr habitat as shown in Table 4. The + + haplochromine cichlids included A. velifer, A. nubila, G. simpsoni, A. alluaudi and P venator. - + - + 10 12

The Nabugabo Ramsar Site 7e Nabugabo Ramsar Site 81 r , I Discussion habitats the key] , Results show that most ofthe native fish species encountered in Lake Nabugabo and wetland area ~ , I during the Cambridge Nabugabo biological survey of 1962 have either disappeared or are threatened with extinction. 0. esculentus, 0. variabilis, P Inshore areas wit] venator and Bagrus docmak were never encountered in Lake Nabugabo during cases low-oxyger the present study. Among the haplochromines, P beadlei, G. simpsoni, and sensitive to low-( A. velifer were the most commonly encountered whereas H. annectidens, A. species in hypox nubila, P multicolor and Astatoreochromis alluaudi were rare in the catches. that some ofthe c P venator was not recorded from Lake Nabugabo. Similar observations have of oxygen, whicl been made in a previous study (Ogutu-Ohwayo, 1993). However, the native as refugia. Subm tilapine 0. esculentus, 0. variabilis, and the haplochromine cichlid P venator spread of the Nil, that have disappeared from Lake Nabugabo still occur in Lakes Kayanja, and conditions. Kayugi. These lakes are thus important refugia for the native fish species that Table 4. Percentage, have disappeared from Lake Nabugabo and should be protected for conservation Kayanja am of the endangered native fish species. Satellite lakes have been found to be important in the conservation of species diversity since they can be closed to fishing and monitored more easily (Mwanja et al., 200 1). • Species

In the present study, fish species diversity in the Nabugabo satellite lakes was Barbus kersternii highest in habitats with submerged and fringing macrophytes Numbers of Brycinus sadleri haplochromines,o. niloticus, 0. variabilis, o.leucostictus, T zillii, C. gariepinus Clarias gariepinus and P aethiopicus were most abundant in near shore areas decreasing outwards Gnathonemus towards the open water whereas that of1. niloticus and Synodontis afrofischeri, victoriae were hig~est in the open water, decreasing towards the near shore areas as shown in Table 3. Fish species diversity decreased with increasing distance Haplochromines from the shoreline, which at all the sites and lakes sampled, was fringed with Lates niloticus aquatic macrophytes. Marcusenius grahami From studies carried out before the introduction ofNile perch, it was observed Oreochromis that the majority of Lake Victoria fishes inhabit shallow inshore waters leucostictus (Beauchamp, 1955/1956). In the 1989 - 1992 survey it was also found that Oreochromis marginal swamps and rocky reefs were important refugia for indigenous species niloticus in Lake Victoria (Kaufman and Ochumba, 1993; Ogutu-Ohwayo, 1993) noted Petrocephalus that many surviving species, especially haplochromines, in Lake Nabugabo catastoma were confined to macrophytes along the lake margin. In addition, survey ofthe Protopterus wetlands surrounding Lake Nabugabo in 1993 to 1994 revealed that several aethiopicus species no longer present in the main lake could be found in the wetland ecotones Tilapia zillii surrounding the lake (Chapman et al., 1995). Since Lake Nabugabo lacks rocky Total no. offish species

82 The Nabugabo Ramsar Site The Nabugabo Ramsar Site habitats the key refugia in the lake are inshore habitats with macrophyte cover and wetland areas. Lake Nabugabo 62 have either Inshore areas with aquatic macrophytes may serve as both structural and in some O. variabilis, P cases low-oxygen refugia for prey species from Nile perch. Nile perch are very rabugabo during sensitive to low-oxygen conditions, which may limit their interaction with prey ;. simpsoni, and species in hypoxic habitats (Fish, 1956). Chapman et af., 1995 demonstrated annectidens, A. that some ofthe cichlids from Lake Victoria could tolerate extremely low levels e in the catches. of oxygen, which may permit these fishes to use structural inshore habitats )servations have as refugia. Submerged and fringing macrophytes also act as barriers to the rever, the native spread of the Nile perch since the species cannot survive under low oxygen ichlid P venator conditions. :es Kayanja, and fish species that Table 4. Percentage contribution of various fish species with distance from the shoreline in lakes .for conservation Kayanja and Kayugi from 2000 to 2002 leen found to be can be closed to Lake Kayanja Lake Kayugi Species Inshore Midshore Offshore Inshore Open water atellite lakes was Barbus kersternii 5.8 12.4 12.1 0.5 0.6 (tes Numbers of Brycinus sadleri 0 0 0 0.4 1.0 'llii, C. gariepinus Clarias gariepinus 2.5 0 0 0.2 0 :reasing outwards Gnathonemus . 0.8 0 0 0 0 antis afrojischeri, victoriae ar shore areas as Haplochromines 7.1 4.5 3.4 5.4 8.8 creasing distance Lates niloticus 64.4 55.1 60.1 60.3 82.0 was fringed with Marcusenius 0 0 0 32.8 0 grahami Oreochromis 14.0 24.7 17.5 0.2 0.7 1. it was observed , leucostictus v inshore waters Oreochromis 0 2.2 0 0.1 0 LS also found that niloticus ndigenous species Petrocephalus 0 0 4.6 0.2 6.6 vayo, 1993) noted catastoma 1 Lake Nabugabo Protopterus 1.1 0 0 0 0.1 tion, survey ofthe aethiopicus 'ealed that several Tilapia zillii 4.7 1.1 1.4 0.5 0.3 ewetland ecotones Total no. of fish 6 mgabo lacks rocky 8 61 10 8 species

e Nabugabo Ramsar Site The Nabugabo Ramsar Site 83 Conclusion and recommendations THE VA~ The information gathered so far indicates that marginal macrophytes provide both structural and physiological refugia for the endangered native fish species Department 0 Tel. 256-41-540765, F in Nabugabo lakes. They should therefore be protected for conservation offish species diversity in these lakes. It has also been observed that lakes Kayugi and Kayanja provide a sanctuary for 0. esculentus, 0. variabilis and some of the haplochromine species that have disappeared from L. Nabugabo. These lakes 'ganda has considerab should therefore be protected to reduce further loss in fish species diversity and though there are only a as a source ofbrood stock for fish farming. region. The native va: the country. A survey I References d January 2001 to asse total of304 plant spec] Beauchamp, RS.A. (1956). The efficient utilization of the fisheries of Lake Victoria. Ann. Rep. E. A[r. abugabo wetland syste Freshwat. Fish. Res. Org.. (1955/56) em are threatened and ( untry's flora that needs Chapman J .L; L.S. Kaufman; C.A. Chapman & F.E. Mackenzie (1995). Hypoxia tolerance in twelve species of East African cichlids: Potential for low oxygen refugia in Lake Victoria. Conserv. BioJ. 9: 1274-1288 . Keyw(J Chapman J. L., Chapman A.C., Schofied P.J., Olowo J.P., Kaufman L.S. & Ogutu-Ohwayo, R (in Press). Biodiversity Lost and Found: Species Resurgence in Lake Nabugabo, East .

Fish, G.R (1956). Some aspects of the respiration of six species of fish from Uganda. Journal of Experimental Biology 35: 186-195

Kaufman, L.S. (1992). The lessons of Lake Victoria: Catastrophic change in species-rich freshwater e task of conservi . Bioscience. 42: 846-858 becoming more ar ntributor to the loss Kaufma'n, L. S. (ed.) (1993). The challenge of the world's great lakes special section: the great lakes of . Africa. Conserv. BioI. 7: 445-730 habitats (Howard, : al., 2000). It is impe Kaufman, L. S. and P.Ochumba (1993). Evolutionary and conservation biology of cichlid fishes as ost priority. revealed by faunal remnants in Lake Victoria. Conserv. BioI. 7: 719-730

Mwanja W., Armouldian A., Wandera S.B., Kaufman L.S., Luzhao W., Booton c., & Fuerst (200 I): ganda has considerab The bounty ofminor lakes: the role ofsmall satellite water bodies in and Conservation . size although there offishes in the Lake Victoria Region, . Hydrobiologia 458: 55-62 er countries in the. Ogutu-Ohwayo. R., (1993). The effects ofpredation by Nile perch, Lates nitotieus on the fish of Lake 06 of which 30 (0.6~ Nabugabo, with suggestions for conservation ofendangered endemic cichlids. Conserv. BioI. 7: 'eas ofhigh diversity (. 701-711 ention (Balmford et j

e identification of c :pecially focused has ., 1994; Kerr, 1996; F shiguvho et aI., 1999; I odrigues et al., 2000). 84 The Nabugabo Ramsar Site