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Of a Comparison of Certain the Biology of Lates East

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Of a Comparison of Certain the Biology of Lates East A comparison of certain aspects of the biology of Lates niloticus (Linne) in some East African lakes Item Type monograph Authors Gee, J.M. Download date 08/10/2021 03:28:47 Link to Item http://hdl.handle.net/1834/34938 ,.g. -- ' , .-" -- - (Rev. Zoo1. Bot. Afr., LXXX, 3-4) (A paru Ie 31 decembre 1969). / ' \ A comparison of certain -of the biology ., / / of Lates (LINNE) East African Lakes (l) J. M. FiS'henies • ~ (Rev. ZooI. Bot. LXXX, 3-4) (A le 31 ecembre 1969). A comparison of certain aspects of the biology of Lates niloticus (LINNE ) in some East African Lakes (1) J. M. €lsnwaJter 'henies eseallxih izartion , INTRODUCTION Lates niloticus (Nile PeI1ch) n Mri­ Lake Albert 1ke Rudolf, but foss]l a er East distribution the . ,ls of [the Lates found in the Miocene beds -of the e otoria basin, (GREENwOOD 195.1) and ,la'ter Pleis1tocene to ene beds in Lake Edward, (GREENWOOD 1959). The present dr-ainage of t:l1e liJ1e 1) is probably a result of the changes took place in the Pleilstocene eras. this ,ime L. niloticus beoame exooct in basil]) above Lake .t but slurviv,ed Rudol,f which was cut off from tJhe -ain ri'Ver became tre drainage ecoloru1zation the present headwater of the Nile was not possible because of the rmation of J:1chison akes Vlictoria Kyoga) 'uhe Semlilci RJapids (isorIatirng Lakes Edward George). separation of from rest of the Nile system, lUibon endemilc faunas ensued, the Oichlidae. Lake w s ,two of Tilapia, five (1) paper was first presented at a Symposium on Man-made Lakes organized by the Ghana Academy of Sciences November 1966. 245 ­ monotypic .genera a -nd at least 120 lc of Ha­ plochromis. The dominate the fish Tilapia ~s long the basis of fi1shing industry whereas Haplochromis although aT -are commencia'loly almos,t ,regarded a « ». The suggestion 1Jhart L. niloticus u A ", .... - ... _ J - -,_ N , , , , D A , t K N A oo/ ~......-;: --~ o 01 " ",,~-,~. ~ , , " , , , f'" ... .. T A N z A N ":.. A ,- 1:4, 000,000 EAST AFRICA Fig. ,1. - Sketch map of the nor thern part of East Mrica ing the position and relationship of the lakes of Nile basin. The tern 9ber n ift 'VaLley,s ar e also 'shown. be Lake otonia as ci.0im.g this ash» eLement in the una was fi,rst mooted in 1928 (GRAHAM l1nce then any arguments have been ,advanced for uch act, (FRYER, 1960 ANDERSON, 1961). n 1955 a !pilot inrtra­ ,was Lake Kyoga a number of lakes and 's n order attempt :seslsmenJt of 1Jhe t of in­ troduction of L. niloticus into ed Since 1963 - 246­ L. niloticus have an ilIlcreas.ingly import3anJt element of ,ciaJl hes on -ke but many of other schemes were of hm!iJted 'SlUocess. L. niloticus lt accidentally gained acoess iJctorua were deli­ -ely introduced, 1964). They now ,iJn numbers becoming more widely s,tfliibuted thToughout the lake -though, as yet, they form only an peY1centage of the mmerci-al catch. The number of 'vations of L. paper is based small due ,the of some the smailil n umbers ar,e t Lake However, such as are avaiJlabl'e yield enough i'nforma'tion that there are t a~n 'fifer.enGes between biology L. niloticus from Lake Albert and Lake hose duced i'nto Lake Victoria and Lake There lis no doubt that L. niloticus be easily and introduced a de variety of waters, both natural and artifiJcial and exhibiJts, for a tropical species, a wide range of for new enviTonments. It is probable that in fiuture ,tlhe species 'lil be used even more uitab~e waters ious parts of the (MIDGLEY 1968), ,and i,t is hoped ,therefore .that he information Ifar ined this l1k may be useful in ,s r,egard. BIOLOGIOAL DATA In the past there has been a considerahle amount of confusion over the systematics of the genus Lates in Uganda and Kenya and authors of the opinion two subspecies of L. niloticus exis·t in Lake A,lbert and Lake Rudo'lf. Ito DAVID d POLL (1937) and WORTHINGTON (1929), Lake Albert contaiJns a shallOW watel' fonm L. n. albertianus a smaUer wa,ter L. n. macropthalamus. SimilaI11y in: ,e Rudolf, WORTHINGTON (1932) 'recogni'ses t'wo subspecies, -a inshore form L. n. rudof.· fianus and a deep water fonm L. n. longispirmis. GREENWOOD (1958) doubtful if this holds d for the Lake klbert Lates a lange of specimens are ined and HAMBLYN (1962) endorses this view, the two subspeci'es merely as ecotypes. HOLDEN (1967) in a based on a large of spe­ ha's conclu sively that L. n. albertianus be mysed with L. niloticus that the deep water ,Dorm muslt 247 be as a di's,tinct speai·es L. macropthalamus (WORTHING­ TON). As yet a similar study ()if of the Lake Rudo'Lf Lates has not been made. The Perch into Lake Kyoga Lake c to­ ria are L. niloticus from the Lake Albert stock, except eight of a Lake Rudolf form, almost certainJy L. n. rudoltianus, were introduced i'n to the Kavirondo Kisumu b y the Kenya Fi'sheries epartment (GEE 1964 ). fore only that llected from Lake Rudolf and La'ke Albert h~ch ,!:Jai'IJ.'s to these ,is us'ed oomparison with the data from Lake ic­ toria Lake Kyoga. Feeding. The predation pnessure and on a in fauna of a newly il.1Jtroduced predator a're est assessed by anaJlysis of the stomach contents of the predator. Stomachs a ber of L. nilo­ ticus from t,he various ,lakes have been d (see Appendix A) ,their tenrts sirrl1P~y analysed n es 1-3. Table 1 shows that between and a ha:Lf and ,five tirrnes as many L. niloticus from Lakes Victoria Kyoga d prey, as from Lakes Albert and Rudolf. This probably a reflection of different prey the different kes . In and Lake Table 1. - An analysis of the stomach contents of Lates. Percentage of fish ~ Vh and nhoo-t nten;bs . I L. Victoria I L. Kyoga I L. Albert I L. Rudolf Number of Lates exam ined 215 108 75 17 % 'stomaoh ,terr1Jt,s 35 52 36 12 % ,Lthout mach conrtellJts 65 48 64 88 Rudolf 1ll10Slt the p otential prey d h ore are y of lange a sitze uo range of L. ni­ loticus and the of ,these and adults smal­ species appear to use of the Ceratophyllum zone and the s'hallOiw ODder to escape predation. Lake Vic­ toria and Lake Kyoga on he other have an abundance of maH Cich'lidae, Mormyridae and , pro­ t - 248­ bably adap ted to ,ding d atJi'on by L. niloticus who h ere­ Dore d ,the capture of food in these new a much easier Table 2 an of the types of pr,ey Ita,ken by L. niloticus in Lakes bert, Kyoga Iiia. num ber of m achs con­ taining ,food Lake dolf is small con­ u sions to b e dnawll. The ndication is ,that L. niloticus do pecifically on amy one or grou p of but are in their .tastes. chl.idae are ,far -the most of fish ioumd in Lakes Victoria and whereas in Lake the aJble 2. - sis contents of Lates. Types of prey taken. L. Victoria I L. Kyoga I L. No. of fish . of No. No. in No. OIl' in ch No. in whi'ch prey n~y p rey rey rey rey ocou rred ccurr,ed occurred i-ed - 37 - 17 - 8 Y'ridae (u.n.ident.) 21 16 - - - - Marcusenius igricans" 6 3 - - -- -- MarcusBnius grahami , 7 4 - - - Alestes jacksoni 6 5 - - - - Alestes baremose + - - - - 6 4 Engraulicypris sp. 13 11 - - 3 3 Barbus p. 6 3 - - - - Clarias sp. 1 1 2 2 - - Lates niloticus - - 1 1 - - 1idae e ntif.) 44 20 - - 10 1 Tilapia sp. 23 12 29 14 1 1 H aplochromis sp. 119 49 181 31 1 1 Caridina nilotica - - - - y 8 eots - 2 - 2 - - s - - 13 5 3 2 BivaJ.'ve m oilluscs 1 1 - - 2 1 suropod llTI ol1uscs - - 2 2 - - 'onomid r v,ae 1 1 - - - - JaIT1t ernaios - - - 3 - - * ecies oocu nriflllg ictOiria Kyoga ly . + Species oocunri'Jljg La'k,e eJ:1t otnly . r - 249­ Tilapia stocks are relatively maller Haplochromis not abun­ dant, only five species being reooJ1ded that ilake. This varyin g faunal 'composi tio n is reflected ,the food of L. niloticus. In Lake Victoria, Cichlidae, r t,ic ul<3 J11y HaplochrOlnis, form the onenrt of diet of L. ,fiound in 50 % of the nh any contents. ynidae lappear rto be the next most important group of prey w.itth CharacLdae and Cyprinidae also making a oant collitribution. In Lake , on la less l§ni£j,oont part f the et of Lates appears to be talken by Alestes s (Cyprinidae) and the 'freshwater prawn Caridina nilotica. HAMBLYN (1966) shown for that L. niloticus :i'l1veJ1tebrates a paJ1t of the diet but above this si,zethey 1tuaUy absent. Table 3 shows that only a ma'H peJ1cel1Jtage of tlhe wirth sto­ mach had than one rprey species in Ithe stomach at anyone Most the L. niloticus had more than one of the s'ame species in , of ch were in approxima­ tely stage of ,that they were more or less y. Tthe 't of prey so far Table 3.. Analysis of stomach contents of Lates. Number of p rey species present. I L. Victoria I L. Kyoga L. Albert er of i'9h d<tJh f1ey 125 42 14 % more e 15 ::> 14 % w,ith 'm are ne of It he same species 47 50 57 % with only one pr,ey 38 25 9 encountered was 35 ·cichilids the ch of a 55 m ·tan­ dard length L.
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