A SURVEY OF FISHES OF THE TANA RIVER AT KORA AND A CHECKLIST OF FISHES OF THE TANA RIVER KEN CAMPBELL, CHRISTOPHER COE AND MICHAEL SAUNDERS

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1 A SURVEY OF FISHES OF THE TANA RIVER AT KORA AND A CHECKLIST OF FISHES OF THE TANA RIVER KEN CAMPBELL, CHRISTOPHER COE AND MICHAEL SAUNDERS Serengeti Ecological Monitoring programme Serengeti National Park, PO Box 3134, Arusha, Tanzania. INTRODUCTION The Tana River drains the southern and eastern slopes of Mount Kenya and the eastern slopes of the Aberdares, and is the largest river in Kenya. It passes through most of Kenya's agro-climatic zones (Sombroek et al 1980) from zone 1-9 (humid and cold) on Mount Kenya and the Aberdares, to VII-1 (very arid and very hot) over much of the lower Tana. The river has received little ecological attention especially in the Kora region and consequently knowledge of the fish fauna is poor. This scarcity of information is largely due to the lack of economic incentives for development and the inaccessibility of much of this region where road communications are difficult and at times impossible. The upper reaches of the Tana, above about 1500m, were examined by van Someren (1952) and notes on the fishes in the middle reaches have been made by copley (1958) Whitehead (1959) made a collection of fishes on the lower Tana River below Garissa. Following this, a single collection has been made, by the Fisheries Department, Kenya, (Oduol, 1976) from six localities on the lower Tana River below Kora. TABLE 1 EXisting and potential Reservoirs along the Tana River, Kenya. Existing Reservoirs Masinga Kamburu Gitaru Kindaruma Kiambere (under construction) planned Reservoirs Usueni Adamson's Falls Grand Falls Kora Hills Karura Output (MW)

2 The Tana River is now the focus of hydroelectric power development in Kenya with four dams in operation, one under construction and further dams at the planning stage (Table 1). Of the potential reservoirs one of the largest is planned for the Kora section of the Tana River (Tana and Athi Rivers Development Authority, 1982). Such impoundments will undoubtedly have a significant effect on the fish populations of the Tana, more so on the migratory species for which provisions are unlikely to be made in future hydroelectric and storage dams since very few Tana River fish species show economic potential. On the other hand a number of species are likely to benefit from the resulting changes in habitat. The present collection serves to establish baseline data on the fish population in the Kora section of the Tana River where the last rapids are situated and from where the Tana emerges onto its flood plain. In addition a checklist is presented of fishes recorded from the Tana River. METHODS Fish species were collected over a 90km stretch of the Tana River spanning the Kora Rapids above Garissa. This stretch of the Tana, which forms the northern boundary of the Kora reserve, can be divided into three main sections; the first from Adamson' s Falls to the start of the Kora rapids, the second constituting the rapids themselves, and the last section at the eastern edge of the reserve below the rapids. Seventeen localitites were sampled within this stretch, sample points being determined by accessability. Fish were captured with the aid of a 10mm mesh seine net, by hand net, by hand line and by lines strung from an otter board held in mid-stream. The seine net accounted for the major part of the collection and was the only technique employed at most sample points. Fish were preserved in the field after initial measurements of standard length and fresh weight. Tentative species identification was carried out in the field and the specimens were later exmined at the Nairobi National Museum. samples were also sent to the British Museum (Natural History) for further identification. RESULTS AND DISCUSSION A total of 1597 fish were captured from seventeen localities. Of these, 348 came from above the rapids, 286 from below the rapids, 52 specimens from a spring towards the western border of the Kora National Reserve, and the remaining 911 from several sites within the Kora Rapids section themselves. Twenty one species were identified (Table 2) and of these ten can be considered common along the Kora stretch of the Tana River. Of interest are two 'species pairs' one of Labeo and one of Barbus, with each 'pair' consisting of a small and a large species; L. greqori and~. mesops,.!!.. oxyrhynchus and B. zanzibaricus. All four species were found to be relatively common at Kora, but only L. greqori is previously recorded or the Tana River. Seven other species of Barbus are recorded from the Tana (see checklist, below), none of which were found at Kora. If these Barbus do in fact represent distinct species it is likely that the Tana River Barbus species have fairly restricted geographical ranges and that different pairs of Barbus may be found along the length of the Tana. This also indicates a degree of specilaistation similar to that found among the cichlid fish fauna of the African Great Lakes (Fryer and Isles, 1972; Greenwood, 1981). Similarly L. gregori is found in the lower Tana whereas L. cylindricus occurs in thelniddle reaches and was not found at Kora. 176

3 TABLE 2 Fish species recorded at 17 sample sites along the Tana River in Kora National Reserve. Species number percent Clarotes laticeps Clarias mossambicus Chiloglanis brevibarbis O. 1 Eutropius depressirostris Synodontis sp Barbus oxyrhynchus B.?:anzibaricus Labeo gregori ~ mesops Labeo sp Sarotherodon sp Anguilla nebulosa Engraulicipris fluviatilis Allestes affinis Glossogobius giuris Petrocephalus catastoma Mormyrus kannume Gnathonemus macrolepidotus O. 1 Discognathus sp. O. 1 Lebistes reticulatus

4 TABLE 3 Fish species Diversity, and Similarity in Species Ccrtposition at Simple Sites in Kora National Reserve on the Tana River. Percent Similarity beoileen Simple Sites S A S M I p T L E E Species Diversity No Nearest Neighbour Linkages Site 11 Site 10 Site 2 Site 1 Site 22 Site 4 Site 13 Site. 3 Site 9 100% 75% 50% 25% I----~

5 FIG. 1 ST~ND~RD ~ 40 z w 5 30 w [ 20 " 10 LENGTHS OF CLAROTES LATICEPS AT FOUR ADJACENT SAMPLE SITES ::n, 50 SITE 22 O'--...L..--'-----'_.L-~~_~~~~_~~_ o LENGTH (MM) 40 SITE o :----:'::~':_:_::':-:..J~_:_:l.-..JI ::.I...-~--~~~~ o LENGTH (MM) 30 SITE f-- r.---- r-- o o LENGTH (MM) 40 SITE Ol..-~""':;'~...l_.l..._..l--'--J..--l~l._..J-~~ o LENGTH (MM) 179

6 'rable 4 Standard lengths of six fish species fran four adjacent sample sites at Kora. Standard T.ell<]th ( Ilia) Site 1 site 21 site 22 Site 23 Species Min I'lean I"iax ~Iin ~Ean Max ~Iin ~Ean Max ~1i II I"i2an I-tlx Clarotes laticeps ~5 No Barbus oxyrhynchus co- No. 26 B. zanzib3.ricus No Labeo greqori No L. meso No. 17 Allestes affinis No Hiver"s edye r lid-stream Sheltered by River"s edge dbove sandbank 100 III below sandbank sandbank

7 species diversity was calculated for sample sites with greater than 40 individuals using the Simpson/Yule index of diversity, taking account of both the number of species and the number of individuals within species ISimpson, 1949). Similarity in species composition between sample sites was calculated using the sorenson coefficient of similarity as modified by Bray and Curtis (1957). A high species diversity was found at each sample point whereas the similarity in species composition between sample points was usually small, even between adjacent localities (Table 3). this situation is illustrated by a comparison between the species composition of localities 1, 4 and 22. sample locality number 1 was situated at the rivers' edge beside the expedition base camp. Locality number 4 was situated approximately 20 km downstream in a backwater within the Kora Rapids. Locality number 22 was situated within 50 metres of locality 1 on the downstream side of a sandbank separating the two sites. Sites 22 and 4 were both in slow flowing or still water and site 1 was near the main channel in relatively fast flowing water. All sites were sampled in a similar manner by seine net. The similarity in species composition between sites 1 and 22 was low but high between sites 4 and 22. The transient nature of the two localities in slow moving or still water indicates a high degree of mobility in those fish species preferring such sites. Species found preferentially in still water were the Mormyrids, petrocephalus catastoma and Mormyrus kanumae; the cichlid, Oreochrornis spilurusi the smaller of the pair of Labeo, L. gregorii, and the smaller of the pair of Barbus, B. oxyrhynchus. The larger of these two I species pairs I were found in. faster flowing water. Also found primarily in the faster flowing water were Allestes affinis, Eutropius depressirostris and the larger catfish, Clarotes laticeps. Within an individual species, site preferences were also observed to change with size (and therefore by inference, age). Clarotes laticeps, a common fish found in most of the localities sampled, showed marked changes in site preference with size I Figure 1). Juveniles of up to 50mm standard length were found in only four out of the 17 sample sites, with 845 of them from site 22, comprising slowly moving water sheltered by a sandbank. Few E. laticeps of this size class were found above the sandbank whereas medium sized fish, from mm, were common. This second group was widespread but found more often in the deeper waters away from the main force of the current. C. laticeps larger than 300mm were only found in the deeper water and were also the only fish caught in the fast moving water. Although smaller numbers were captured, data from four sample sites shows a similar distribution of size between adjacent sample sites for a number of other species (Table 4). The seperation in both size and site preference between the small Barbus oxyrhynchus and the larger B. zanzibaricus is clear. Labeo gregori and L. mesops were both found almost exculsively at a single sample site, sheltered by a sandbank (site 22) b~t within this locality no overlap in size was observed. unlike the previous species, in Allestes affinis an overlap in size ocurred between sites 1 and 22, above and below the sandbank. However, the smaller ~. affinis, below 132mm standard length, were only found in the more sheltered water (site 22). ANNOTATED CHECKLIST OF TANA RIVER FISHES The following list of fish species recorded from the Tana River 'is taken from available literature and from the results of the survey carried out at Kora, Estuarine and marine species confined to the delta of the Tana River are not considred here. 181

8 protopterus amphibius (peters) 1844 This species was recorded as!.. amphibia (Owen) by Copley (1958), being distributed in the lower 40 miles of both Tana and Athi Rivers as well as in waterholes at Afwain, near Garissa. Trewavas (1954) redescribed this species and noted its distribution in East Africa as being between Lake Turkana and the Lorian Swamp, in the coastal belt near the rivers Tana and Athi, and in the delta of the zambezi. Whitehead (1959) notes!.. amphibius as being fairly common in floodwater pools and swamps near the Tana and Athi Rivers. No material collected at Kora. Mormyrus kanumae (Forskal) 1775 Noted from the Tana River by copley ( 1941, 1958) whilst Whitehead ( 1959) records a mormyrid species from the upper Tana and from the lower Tana at Garsen and suggests that M. kanumae is present in both the Athi and Tana Rivers.!:!.. tenuirostris (peters) and!:!.. hildebran<1ti (Peters) have been recorded from the Athi river by Boulenger ( ) but he tentatively synonymized M. hildebrandti with!:!.. kanumae. A Mormyrus species was recorded by Mann (1967) in the upper Tana. A Mormyrus species, probably!:!.. kanumae was collected at Kora in the relatively sheltered an muddy conditions occuring downstream of a sandbank. Gnathonel!lUs sp. A single adult and some juveniles were caught by Whitehead (1959) on the lower Tana at Hola, and in the Tana Delta at Garsen, Wema a.od Golbanti, and were tentatively assigned to Q.. macrolepidotus (Peters). This is a widespread species in the eastern rivers of Africa. A single specimen was collected at Kora, Petrocephalus catastoma tanensis First recorded from the Tana River from below Garissa by Whitehead (1959).!.. degeni and!.. stuhlmani were synonymised with!.. catastoma by Whitehead and Greenwood (1959) but the Tana River specimens were given subspecific status on the basis of a high dorsal ray count. This species was common at Kora where it congregates in shoals in the more sheltered stretches and pools. Allestes affinis The type specimens are described from the Tana River at Merifano in the Tana Delta (Boulenger ). Also recorded by Copley (1958) and by Whitehead (1959) as being common in all localities between Garissa Ngau. Found in small numbers in most localities at Kora, both above and below Kora Rapids. Specimens of A. nurse recorded from the Tana by Copley (1958) may be misidentifications-of A. affinis. Labeo cylindricus Boulenger ( ) records specimens from the Mathioya River (Tana basin), and the species is mentioned by Copley (1941, 1958) from the Tana and its tributaries. Whitehead (1959) refers to~. cylindricus in the middle reaches of the Tana. No specimens were positively identified at Kora, although a single specimen from below the Kora Rapids may belong to this species. It seems likely that this species is replaced by~. gregori in the lower parts of the Tana River. 182

9 below 140nun SL were found to have no adipose fin whereas this was present in all specimens above this size. Clarias mossambicus A widespread species in East Africa and specimens are recorded from the Tana by Boulenger ( ) and by Copley (1958). Whitehead (1959) notes that this species is common up to about 1200m above sea level and Mann ( 1967) reco"as that the species is not known from above Grand Falls on the Tana River, this being quoted by fishermen as being the upper limit of their distribution. present at Kora in small numbers. Clarias lazera Copley (1958) recolids the Tana River as being within the distribution of this species but there are no records from the Tana. Eutropius depressirostris Recorded from the Tana by Boulenger ( ) and by copley (1958), whilst whitehead (1959) notes that it is common up to about 900m above sea level. This species was amongst the more commonly caught fish at Kora. Both Boulenger ( ) and Copley (1958) record Schilbe mystus as occuring in the Tana Riv~r, bit his may be a missidentifiaction E. depressirostris, since S. mystus is otherwise recor~ed from the Lake Victoria drainage system. Physalia somalensis tanensis First recorded from the delta of the Tana River by Whitehead (1959) and separated from~.~. somalis by a smaller number of anal rays (Whitehead, 1962 a). Not recorded at Kora. Synodontis sp. A number of Synodontis species are recorded from the Tana river. Whitehead (1962 b) gives two species, ~. serpentis and~. zambezensis. Species of Synodontis from the eastward flowing rivers of Africa are poorly known and further work is required to clarify the relationships between them. The Synodontis from Kora appear to be mid way between that from the northern Uaso Nyiro River,.. geldensis, known only from two specimens, and the I typical' ~. zambezensis. This latter species may in fact consist of a number if separate species or races. Only a single Synodontis was caught at Kora, ~. serpentis (Whitehead, 1959) not being present among the samples. However, a wide morphological variation was apparent within the samples, this is only partly explained by sexual dimorphism, making positive identification difficult for small samples. The colouration is also highly variable, juveniles having a reticulate pattern which slowly changes with size to become lighter and more uniform. Since the second Tana River species is presently known as S. zambezensis, those the Kora specimens ~ere tentatively identified as S. 'zambezensis'. Chiloglanis brevibarbis Only a single specimen was recorded at Kora. Both Boulenger ( ) and Copley (1941, 1958) record this species from the Tana basin, and Mann (1967) records it as common in rapids along the Tana. It is likely that his species is more common in the upper reaches of the Tana River and its tributaries where there are a greater abundance of rocky habitats. 183

10 Labeo gregori ---;rhe type specimen is recorded by Boulenger ( ) from Merifano in the Tana Delta. Copley (1958) lists this species from the Tana but suggests a synonomy with ~' cylindricus. Whitehead (1959) records~. gregori in the lower reaches of both Tana and ~thi Rivers. This small Labeo was the most commonly caught fish at Kora. r...abeo mesops A second Labeo species identified as ~' mesops was also found to be common at Kora. Not recorded previously from the Tana RiverI this species is found in the Zambesi and Shire Rivers and its distribution extends northwards in east coast rivers to the Juba River in somalia. Discognathus hindii Recorded by Copley (1958) from tributaries of the Tana and Athi Rivers. A single specimen, probably of this species, was found at Kora. Discognathus dembeensis Recorded from Kilimanjaro by Boulenger ( ) but from Nairobi River by Copley (1958). There are, however, three Nairobi Rivers in East Africa, one in the Tana basin, one in the Athi basin and one in the Lake Victoria basin. It is most likely that copley meant the one flowing into the ~thi River. Barbus oxyrhynchus Very common at Kora where it is the smaller of the two Barbus species present. Not previously recorded from the Tana River. Barbus zanzibaricus The larger of the two Barbus species found at Kora. recorded form the Tana River. Not previously other Barbus species In addition to those recorded at Kora seven other Barbus species are recorded from the Tana River by Boulenger ( ), Copley ( ), Whitehead (1959), Greenwood (1962) and Mann (1967). These are B. amphigramma, B. gregorii, B. labiatus, B. mariae, B. perplexican, B. tanensis and B~neumayeri. There is an urgent requirement for collections of Barbus species from all part of the Tana River, from the delta to the tributarieb on the Aberdare Range and Mount Kenya, before the Tana River Barbus can be fully understood. Engraulicypris fluviatalis First recorded from the Tana River by Whitehead (1959) and described by Whitehead (1962 a), from floodwater pools near to Garissa. This species was commonly encountered at Kora in backwaters and other slow moving stretches of the river. Clarotes laticeps Boulenger ( ) records this species from Ngatana (probably the Tana River) and Copley (1958) records its occurance from the Tana and adjacent rivers. Whitehead (1959) records a single small specimen from a floodwater pool near Garsen in the Tana Delta. This species was common at Kora where specimens ranging in size from 13mm standard length (SL) to 528mm were caught (representing fish of up to 2900g) small specimens of 184

11 Amphilius grandis The types of this species were described by Boulenger ( ) from the Chania River in the upper reaches of the Tana basin. Copley (1958) notes its distribution in those rivers flowing off the Aberdare Range and Mount Kenya. Mann (1967) also recorded three specimens at the Merilla barrage on the lower Tana. No specimens were recorded at Kora. Anguilla sp. Three species of eel are recorded from the Tana River. A. nebulosa is the more common (Frost. 1955). whilst~. mossambica and A. bicolor are rarely recorded. Four species including three adults and one juvenile, were caught at Kora. The construction of reservoirs on the Tana River may have serious consequences for the long term survival of these species in the Tana. especially in its upper reaches. Oreochromis spilurus Common at Kora especially in the quieter stretches. The specimens captured Members of this genus are recorded from the Tana by Copley (1958) as Tilapia nigra (with four anal spines) and as 1:. mossambica (with three anal spines) by Whitehead ( c). The three Tilapine genera Tilapia. Sarotherodon and Oreochromis were formerly included as subgenera in the broad genus Tilapia (Trewavas. 1966a and b) and may still conveniently be known as I the TilapiasI. Sarotherodon was given generic rank by Trewavas (1973) and later split into Oreochromis and Sarotherodon (Trewavas ). Oreochromis spilurus is divided into three forms each with sub-specific status (Trewavas. 1983). 2. ~' spilurus having a predominance of individuals with three anal spines, o..!._ nigar with four anal spines, and O. ~.percivali which is an isolated population found in springs at Chandler's Falls on the Northern uaso Ngiro River. The specimens captured at Kora include both three and four spined fish, with three spined individuals predominating (78%). Three spined individuals are more commonly encountered in the lower reaches of the Athi River. below Lugard' s Falls which is thought to form a barrier to upstream movement. Four spined fishes are found above this point (Trewavas. 1983)../1. similar situation probably exists in the Tana with four spined fishes more common in the upper reaches and three spined in the Lower Tana. The large number of introductions of various Oreochromis species into impoundments within Kenya, their subsequent escape into the river system and the readiness with which hybridisation occurs. has created a confusing taxonmic situation amongst members of this genus. Glossogobius giurus A widespread species in coastal and estuarine waters around the Indian Ocean. Whitehead (1959) recorded juveniles of this species in floodwater pools as far upstream as Garissa. Three specimens, including one adult, were recorded at Kora. Mann (1967) remarks. citing information from fisherman. that Grand Falls may mark the upper lia:it of this species on the Tana River. Introduced Species salmo gairdneri Recorded from the upper reaches of the Tana River and its tributaries by van Someren (1952). An introduced species whose distribution is limited 185

12 by the 15 [e isotherm at about 1500m above sea level. Although some breeding may occur in the wild, a significant portion of the population are artificially stocked either directly in the rivers, or through escapes from fish farms. Salmo trutta This species was initially in a number of impoundments and rivers but unless natural breeding occurs is unlikely to be present in the Tana at the present day. Lebistes reticulatus This American species is now found over large portions of both the Athi and Tana Rivers. Twenty eight specimens were captured, the majority of these from a spring towards the west.ern edge of the Kora National Reserve ~ Gambusia affinis Another Amerian species introduced into Africa for mosquito control. No specimens were found at Kora but the species is recorded from the upper Tana (Mann, 1967). 186

13 REFERENCES Boulenger, G.A. ( ). Catalogue of the Freshwater Fishes of Africa in the British Museum (Natural History), London. Bray, J.R. and Curtis, C.T. (1957). An Ordination of the Upland Forest CommWlities of southern Wisconsin. Ecological Monographs. 27: Copley, H. (1941). A short Account of the Freshwater Fishes of Kenya. Journal of the East Africa Natural History Society, 16: 1 (70), Copley, H. (1958). Common Freshwater Fish of East Africa. H.F. & G. Winterby Ltd., London. Frost, W.E. (1955). Observations on the Biology of Eels, (Anguilla spp.) of Kenya Colony, East Africa. Colonial Office Fisheries publication, 6, 1954, H.M.S.O., London. Fryer, G. and Iles, T.D. (1972). The Cichlid Fishes of the Great Lakes of Africa, their Biology and Evolution. Oliver and Boyd, Edinburgh. Greenwood, P.H. (1962). A Revision of Certain Barbus species (pisces, Cyprinidae) from East, central and south Africa. Bulletin of the British Museum (Natural History) zoology. 8, 4, Greenwood, P.H. (1981). the Haplochromine fishes of the East African lakes. Kraus International publications, Munich. Mann, M.J. (1967). A preliminary Report on a Survey of the Fisheries of the Tana River, Kenya. Survey of the Irrigation potential of the Lower Tana River Basin, volume 7, Appendix M- Infrastructure and Secondary Development, Food and Agriculture Organisation of the united Nations, Acres International, Canada, and International Land Development Consultants N.V., The Netherlands, Anex M-Ill p Simpson, E.H. (1949). Measurement of Diversity. Nature. 163: 688. Sombroek, W.G., H.M.H. Braun and B.J.A. van der pouw, (1982). Exploratory Soil map and Agro-climatic zone Map of Kenya, Republic of Kenya, Ministry of Agriculture National Agricultural Laboratories, Kenya Soil Survey, Exploratory Soil Survey Report no. E1, Nairobi, 1982, pp 56, and 4 maps. van Someren, V.D. (1952). The Biology of Trout in Kenya Colony. GOvernment printer Nairobi. Tana and Athi Rivers Development Authority, (1982). Tana Delta Irrigation project, Feasibility Study. Haskoning B.V., The Netherlands and Mwenge International Associates Ltd., Kenya. Trewavas, E. (1966 a). Tilapia aurea (Steindachner) and the status of Tilapia nilotica exsul..!._ monad! and.!_ lemassoni (pisces, Cichlidae). Isreal journal of zoology. 14: Trewavas, E. (1966 b). Fishes of the genus Tilapia with four anal spines in Malawi, Rhodesia, Mozambique and southern Tanzania. Revue Zool. Bot. afr. 74: Trewavas, E. (1973). On the cichlid fishes of the genus pelmatochromjs with proposal of a new genus for ~. congicusi on the relationship between pelatochromis and Tilapia and the recognition of sarotherodon as a distinct genus. Bulletin of the British Museum (Natural History) Zoology. 25: Trewavas, E. (1982). Generic groupings of Tilapiini used in aquaculture. Aquaculture. 27: Trewavas, E. (1983). Tilapine Fishes of the genera sarotherodoon, oreochromis and Danakilia. 583pp. British Museum (Natural H~story), London. 187

14 Whitehead, P.J.P. (1959). Notes on a Collection of Fishes from the Tana River below Garissa, Kenya. Journal of the East Africa Natural History Society. 23, 4 (101); Whitehead, P.J.P. (1962 a). Two New River Fishes from Eastern Kenya. Ann. Mus. Civ. storia. Nat. Genova, 73; Whitehead, P.J.P. (1962 b). A New Species of Synodontis (Pisces: Mochokidae) and Notes on a Mormyrid Fish from the Eastern Rivers of Kenya. Revue Zoologique et Botanique Africainne. 65, 1-2; Whitehead, P.J.P. (1962 c). The Relationship between Tilapia nigra (Gunther) and T. mosambica (Peters) in the Eastern Rivers of Kenya. procedings of the Zoological Society of London, 138, 4;

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