A Note on the Fishes of Lake Jipe and Lake Chale on the Kenya-Tanzania Border. Item Type Journal Contribution Authors Dadzie, S.; Haller, R.D.; Trewavas, E. Download date 01/10/2021 04:07:07 Link to Item http://hdl.handle.net/1834/7784 @ Page 46 No.l92 A NOTE ON THE FISHESOF LAKE JIPE AND LAKE CHALE ON THE KENYA.TANZANIABORDER StephenDadzie', Rene D. Ilaller'& EthelwynnTrewavas ' G Lake Jipe is a shallow basin at about 3' 40' S 37' 40' E, east of the North Pare Mountains in Tanzania.Chala is a smallerlake lying in a rocky craterabout 19km north of Lake Jipe. In 1951, whenitwas visitedbyDr.Inwe-McConnell(thenMissR.H.Lowe)LakeJipewasabout 12miles ( 19 lnn) long and 1.5 miles (2 km) wide andonly a few feet deep. Its northernend is a swampinto which flows a stream, known in Kenya as the Lumi, from Mount Kilimanjaro. From its northwesternend issues,at least in wetter periods,the River Ruvrt' headwaterof the long river formerly known by that name,but now called the Pangani,the nameof the town at its mouth on the Indian Ocean.Since the formation of the barragelake Nyumba ya Mungu (NYM) in the upper PanganittreRuvuflowsfromLakeJipeintotheswampynorth-eastcornerofthislake.I-akeJipe's swampyedges are surroundedby semi-aquaticgnsses and reeds,and patchesof water-weeds (Najas mdPotamogeton\ spreadtheir leavesand flowers on its surface. Numerouswater bfuds prey on the lake's faunaand these and hippopotamus fertilize the water. The sketchby Sir llarry Johnston,reproduced here from his book of 1886,gives an idea of the lake's appearanceas it remainstoday, (Fig. l). At Taveta,NE of Lake Jipe, the well-known pioneerColonel E.S. Groganhad settledafter the SecondWorldWarandestablishedafarmincludingfish-pondsstockedfromLakeJipe. lakeJipe and Chalaand the Tavetaponds were visited in 1951by Miss Lowe, who was then a memberof ttreEast African FisheriesResearch Organisation at Jinja, Uganda. Shecollected fishes from the pondsand both lakes. The two tilapiine speciesof L:ke Jipe proved !o havebeen undescribed. Shethen ravelled on to Korogwd on the Lower Pangani,where lv{ajor R.E. Gould, then fish culnrist to the TanganyikanClanzania) Government, had establishedfish-ponds in which he reared tilapiine speciespreparatory to using them for stocking dams and ponds. Among his speciaswere the two endemictilapias from lake Jipe and npo from the River Panganiand these were the subjectof Inwe's paperof 1955,where they were namedTilapia jipe and T.girigan (I-akeJipe)andT.panganimdT.mossarnbicakorogwe(RiverPang;ani).Thelastnamedwaslater givenfull specificstatusby Trewavas (1983)andall fourwere included in thegenvsOreochromis. The generic tnrne Oreochromishad beenproposed for O.hunteri by Gunther in 1889,a name meaning 'mountain Chromis' in referenceto its habitat in Lake Chala on the slope.sof the Kilimanjaro volcanic mass.(Chromis is.a name that had been used for severalcichlids, but really belongsto a marine genus.) a.' -t.l rDept.of Zoolory,University of Nairobi,P.O. Box 30197Nairobi tl 'BaobabFarm, P.O. Box 902(D,Mombasa I 3cloBritish Museum (Nahral History), Imdon SW?5BD, England aThe Ruvu of Baileyet al., 1987,not of Bailey,1959. The laBer is alsoknown as the Khgani drd enters :l the Indian Ocean at Bagamoyo. t Not the Korogwe at the entry of the Ruvu to I.IY1r,I (Bailey et d., l97E) No.l92 Page 41 The situationin 1951and until recentlywas therefore that Lake Chalacontained one endemic tilapiinespecies,O.hunteri,andLakeJipetwo,Ojipemdo.g.girigan.L,owe(1955)recognised that fry of O.girigan were difficult to distinguishfrom O.panganiand Trewavas(1983) consideredthese two formsto be only subspecificallydistinct. Oneof us (R. Haller),has, since May 1976,been taking Oreochromis from Lake Jipe for culture at BaobabFarm, nearMombasa. In January1983 a third tilapiine specieswas found in the Lake anda brood of youngabout 2.5cm long wastaken to BoabobFarm and rearedto maturity which tleyreachedatanageof9monthsandatotallengthof1G18cm. Asampleofthese,fiveofeach sex, was sentto the British Museum(Natural History) tBMNlIl and identified u Oreochromis esculentus(Graham). Anotherof us (S.Dadzie) visited the lakes in March-April,1985, and found in LakeJipe, as well as the two endemic Oreochromis md O.esculenfusseveral specimensof Tilapia rendalli Boulenger.Froml:keChalahecollectedT.rendalliandalargespecimenofO.p.pangani,aswell as the endemic O.hmteri. We haveno doubtthat?.esculentu,s,TilapiarendalliandO.p.panganiwere introduced to these lakesfrom tle Tanzaniaside, either deliberatelyor in the caseof Lake Jipe by migration up the Ruvu River. The first two are not native to the areaand no tilapine exceptO.hunteri was previouslyknown from LakeChalaalthough this species hadbeen collected there and specimens sentto the BMNH on five occasions,registered in 1889,19U.,1946,1952 and 1980. Non-tilapiinefishes also present in Lake Jipein l95l (Lowe, l95l) wereA statotilapia bloyeti (Sauvage),Clarias massambicusPeters, Barbus paludinosusPeters and Petersius tangensis Lonnberg.Astatotilapia bloyeti wasfound also in lake Chalaby W.P.Scott in 1977andagun by Dadziein 1985. Specimensof theintroduced species and the non-tilapiines were sent to theBMNH andidentified by E.T. The IntroducedSpecies Gould( 195I ) publisheda list of thespecies that he had imported for cultureto Korogwe.Among themwereO.esculentusandO.variabilrs,speciesendemicintheLakeVictoriabasin,and,Tilapia rendalli6and O.macrochir from pondsin Katanga(now Shaba). O.esculentusis a mouth-brooder,now commonin severaldams and lakes in Tanzania,including Nyumbaya Mungu(see Bailey etal., 1987and Trewavas, 1983), whichprobably acquired it from stockedponds and backwatersin the flooded area. For food it has a strong preferencefor phytoplanktonin openwaters. This was shownby observationin its original habiaL the Lake Victoria basin(for referencessee Trewavas, 1983), in experimentalponds Payne, 1971) and in Nyumbaya Mungu(Bailey et al. 1978). Its weakjaws and minuteteeth are unsuitedeither for "Referred to as T. n'elanopleura, a name no longer in use. Page 48 No.l92 scrapingalgal growths from stemsand leaves or for biting andchewing higher plants. In NYM, althoughit succeededin establishingitself as a proportionof the tilapiinefauna, its growth in lengthwas inferiorto thatof tle speciesof local ongin(O.p.panganiandO jipe) andalso to that in its originalhabitat. In NYM very few specimensexceeded 22cmin total lengthand 350 g in weight,whereas males of Oj ipe andO.p.pan gani grewto between32 and 3 8 cm wit h a maximum weightoflSmg @aileyetal.,1978,figs3&4).Amale O.esculentuscollectedfromNYMin 1980by A.I. Paynewas nearly ripe at TL 17cm; this is aboutthe sameas the lengthof mature fishesrearedatBaobabFarmforg montirs(16-18 cm)andthatrecordedby Lnwe (1955) inponds atKorogwe(16-19cmatanageofunderTmontls).InLakeVictoriatheminimumlengthatfirst maturitywas recorded as 19 or20-21cm at differentlocalities, but mostdo not breeduntil they ueZ?cmormore intotallength(Lowe-McConnell;1956,Ganod,1959). Theygoontoreach TL of 30 cm or more. Tilapia rendalli,a substrate-brooderand guarder of the young,is oneof the largestof is genus. It is a voraciousfeeder on aquaticand semi-aquatic higher plants. Ruwet (1962 and 1963) gives a vivid descriptionsof its feedingin thebarrage Lake Mwadingusha in thecourse of RiverLufira, Shaba.The lakewas shallow, mostly less than 4 metresmaximum depth, and in dry seasonsor whenthe rains were deficientthe draw-down at theelectricpowerstation was so great that thc lake shrankto a fractionof its maximumarea and semi-aquatic vegetation was able to intrudeover vast stretches.When rain againflooded the lake T.rendalliimmediately attacked flooded grasscs. Ruetdescribes the eventas follows (ranslationfrom the accountof 1963): "I have often halted in a canoein ttre middle of the immensemeadows dominatedby Oryza,the wild rice. I still rememberthe continuouscracking soundproduced by hordesof (T.rendalli)tearing, cutting and browsing on the floodedstems, leaves and rhizomes of Oryza. Frommid-March, under the joint activityof thousandsof thesefishes, the edge of themeadows from Kinshasha to Shinangwa,that is, overa distanceof aboutl5 Km, retreatedby about8-10 metres". Dr G.B. Bernascek,in a letter dated24.VI.1980 reported that the introductionin l95l of T.rendallialoa denselyvegetated lagoon near the mouth of RiverLupululu in southemTanzania hadresulted in its clearanceto form a lakeofopen water. Suchare the two speciesnow introducedinto lake Jipe. The EndemicTilapiines WhatisknownoftheecologyoftheoriginalinhabitantsisduetoLowe(1955)andBaileyetal. +: (1978).Theyaremouth-brooders,withacharacteristicformofnest(matingtenitory). Stomachs 1 of O.p.girigan from LakeJipe contained fragments of water-lilyplants and epiphytic algae from NaJasst€ms and leaves. The coarseteeth of this speciesare well suitedto sucha diet. Lowe's T'. few specimens of Ojipe from LakeJipe did not provideinformation about its naturalfood. In the Korogwewas restrictedo pondsboth this andO.p.girigan feAon detritus,but Ojipe, finer particlesa differenceconesponding to thedifference between them in thepharyngeal dentition. In NYM both Ojipe andthe indigenousO.p.pangani fed on periphyton. Page50 No.l92 Sardineraps, alsosetatthe shallow edges, catch exclusively the smallPetersius ("sardines") that form schoolsin the lake(Information from the KenyaFisheries Department). At the smallerbut deeperLake Chalathere are 7 registeredfishermen of whom2 operateregularly. Fishing in both lakesis for marketingas well as for subsistence.The fields are thereforeof legitimateconcern, and