Trophic interrelationships and food-webs among the fishes in ecosystems of the Victoria and Kyoga lake basin

The Victoria and Kyoga lake basins had a high fish species diversity with many fish speciesthat were found only in these lakes. Two Tilapiines species Oreochromis esculentus andOreochromis variabilis were the most important commercial species in these lakes and werefound nowhere else on earth except in the Victoria and Kyoga lake basins (Graham 1929,Worthington 1929). Lakes Kyoga and Nabugabo also had endemic haplochromine species(Worthington 1929, Trewavas 1933, Greenwood 1965, 1966). As stocks of introducedspecies increased, stocks of most of the native species declined rapidly or disappearedaltogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, someselected satellite lakes from the two basins namely Lakes Mburo, Kachera, Wamala,Kayanja, Kayugi, Nabugabo, Victoria, Victoria nile and River Sio(Victoria lake basin).Lakes Kyoga (Iyingo), Nawampasa, Nakuwa, Gigati, Nyaguo, Agu, Kawi and Lemwa(Kyoga lake basin).Species composillon and relative abundance of fishes were estimated by detennining theoverall average total number of each species encountered. A trophic consists of species usingthe same food category. Shannon-Weaver Index of diversity H (Pielou, 1969) and number oftrophic groups, were used to estimate the Trophic diversity of various fish species in the lakes.Food analysis has been done on some fishes in some of the sampled lakes and is still going on,on remaining fishes and in some lakes.Generally fish ingested detritus, Spirulina, Melosira, filamentous algae, Planktolyngbya,Microcysists, Anabaena, Merismopedia, Spirogyra, higher plant material, rotifers, Ostracodes,Chironomid larvae and pupae, Choaborus larvae, Odonata, Povilla, Insect remains, Caridina, fish eggs and fish. Eight trophic groups were identified from thes food items ingestes. These included detritivores, algae eaters, higher plant eaters, zooplanktivores, insectivores, molluscivores, prawn eaters, paedophages and piscivores.Trophic diversity by number of trophic groups was highest in Lake Kyoga (6) followed by lakes Kayugi, Nabugabo, River Nile and Mburo (3) and the lowest number was recorded inkachera (2).

Bibliographic Details

Main Authors:	Mbabazi, D., Ogutu-Ohwayo, R., Wandera, S.B., Namulemo, G.
Format:	book_section biblioteca
Language:	English
Published:	Fisheries Research Institute 2000
Subjects:	Ecology, Fisheries,
Online Access:	http://hdl.handle.net/1834/35234
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