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Biology, ecology and the fishery of Mukene, Rastrineobola argentea
Full text linkFood and feeding, condition factor, breeding periods, growth and size at first maturity of
a small pelagic cyprinid Rastrineobola argentea (P.) in Lake Victoria are determined.
Fishing gears and methods that have been used in the exploitation of the species and
could be harmful to the fishery are outlined. Management measures leading to possible
sustainable exploitation of the fishery are suggested.
Adult R. argentea feed on zooplankton during daytime. Juveniles feed on planktonic
early instars of lakefly larvae. Although the species breeds throughout the year, two
breeding peaks were observed during the drier months of August and December January.
Least breeding was observed in the rainy months of April-May and October November.
Fishes from the open water station at Bugaia showed higher numbers of
breeding individuals than those from inshore areas. The mean monthly condition factor of
fish from Napoleon Gulf confirmed breeding peaks as obtained from the number of fish
with ripe gonads.
The species showed a mean instantaneous growth rate (K) of 1.75 and attains length
infinity (Lx) of 54mm. Females of the species in these waters show a reduced size at
maturity as compared to ten years ago when exploitation of the species was at minimal
levels. The males have however not changed much
The biology and ecology of Lake Victoria fishes: their development and management
No full textFood and feeding, condition factor, breeding periods, growth and size at first maturity ofa small pelagic cyprinid Rastrineobola argentea (P.) in Lake Victoria are determined.Fishing gears and methods that have been used in the exploitation of the species andcould be harmful to the fishery are outlined. Management measures leading to possiblesustainable exploitation of the fishery are suggested.Adult R. argentea feed on zooplankton during daytime. Juveniles feed on planktonicearly instars of lakefly larvae. Although the species breeds throughout the year, twobreeding peaks were observed during the drier months of August and December January.Least breeding was observed in the rainy months of April-May and October November.Fishes from the open water station at Bugaia showed higher numbers ofbreeding individuals than those from inshore areas. The mean monthly condition factor offish from Napoleon Gulf confirmed breeding peaks as obtained from the number of fishwith ripe gonads.The species showed a mean instantaneous growth rate (K) of 1.75 and attains lengthinfinity (Lx) of 54mm. Females of the species in these waters show a reduced size atmaturity as compared to ten years ago when exploitation of the species was at minimallevels. The males have however not changed much.All chapters begin page 1.
On title page: Ugandan version.
Chapter 2
The biology and ecology of lake Victoria fishes: THeir development anf management
No full textMost fish in Uganda comes from lakes Victoria, Albert, Kyoga, Edward, George, about 160 minor lakes and rivers. Fish production of most lakes in Uganda has changed considerably since development of most of the fisheries started during the first half of the 20th century. Analysis of the changes that have taken place in these fisheries provides useful information on the potential and management issues associated with fisheries in Uganda. Total national fish catch statistics are not available for the period prior to 1960. The trends in total fish production from the different water bodies between 1961 and 1995 are illustrated in Figure 3. Total fish catches were 60,000 to 71,000 metric tonnes between 1961 and 1965 and increased after 1965 reaching a peak of 245,000 metric tonnes in 1990. The increase from 1965 to the late 1970s followed establishment of introduced Nile perch and Tilapiines to Lake Kyoga which reached a peak in 1978 and then declined. The second peak followed establishment of the same introduced species in Lake Victoria. This too peaked in 1990 after which catches declined. During I970s, most of the fish came from Lake Kyoga while during the 1980s it was from Lake Victoria. Although the above trend shows an increase in total fish catches, historical trends in fisheries have been of decreasing catches especially of more desirable species. This impression can only be appreciated through examination of historical changes in individual fish production systems. The trend in total catches from major water bodies is illustrated in Figure 4. A brief analysis of the fish stocks and fish production from the different water and the efforts to manage the fisheries of the major lakes is given.On title page: (The Ugandan Version
The biology and ecology of Lake Victoria fishes: their development and management
No full textCatch effort data on which fisheries management regulations are sometimes based are not available for most lakes in Uganda. However, failure to regulate fishing gears and methodshas been a major cause of collapse of fisheries in the country. Fisheries have been damagedby destructive and non-selective fishing gears and methods such as trawling and beach seining, by use of gill nets of mesh size which crop immature fish and by introduction ofmechanised fishing. Selectivity of the gears used to crop Lates niloticus 1. (Nile perch),Oreochromis niloticus 1. (Nile tilapia) and Rastrineobola argentea (Mukene) which are currently the most important commercial species in Uganda were examined in order torecommend the most suitable types, sizes and methods that should be used in exploiting thesefisheries . Gill nets of less than 127 mm mainly cropped immature Nile ti1apia and Nile perch. To protect these fisheries, the minimum mesh size of gill nets should be set at 127 mm.Seine nets of 5 mm do catch high proportions of immature Mukene while those of 10 mmcatch mainly mature Mukene. When operated inshore, both sizes catch immature Nile perchand Nile ti1apia as by-catch. To protect the Mukene fishery and avoid catching immature byecatch,a minimum mesh size of the Mukene net should have been 10 mm operated as Lamparatype net offshore but since most fishennen have been using the 5 mm seine for over five years the minimum size should not be allowed to drop below 5 mm pending further thoroughinvestigations. Beach seining, trawling and are destructive to fisheries and should beprohibited until data that may justify their use is available.All chapters begin page 1.
On title page: Ugandan version.
Chapter 11B
Fishing gear selectivity of Lates niloticus L. (Nile perch), Oreochromis niloticus L. (Nile tilapia) and Rastrineobola argentea Pellegrin (Mukene) in lakes Victoria, Kyoga and Nabugabo
Full text linkCatch effort data on which fisheries management regulations are sometimes based are not available for most lakes in Uganda. However, failure to regulate fishing gears and methods
has been a major cause of collapse of fisheries in the country. Fisheries have been damaged
by destructive and non-selective fishing gears and methods such as trawling and beach seining, by use of gill nets of mesh size which crop immature fish and by introduction of
mechanised fishing. Selectivity of the gears used to crop Lates niloticus 1. (Nile perch),
Oreochromis niloticus 1. (Nile tilapia) and Rastrineobola argentea (Mukene) which are currently the most important commercial species in Uganda were examined in order to
recommend the most suitable types, sizes and methods that should be used in exploiting these
fisheries . Gill nets of less than 127 mm mainly cropped immature Nile ti1apia and Nile perch. To protect these fisheries, the minimum mesh size of gill nets should be set at 127 mm.
Seine nets of 5 mm do catch high proportions of immature Mukene while those of 10 mm
catch mainly mature Mukene. When operated inshore, both sizes catch immature Nile perch
and Nile ti1apia as by-catch. To protect the Mukene fishery and avoid catching immature byecatch,
a minimum mesh size of the Mukene net should have been 10 mm operated as Lampara
type net offshore but since most fishennen have been using the 5 mm seine for over five years the minimum size should not be allowed to drop below 5 mm pending further thorough
investigations. Beach seining, trawling and are destructive to fisheries and should be
prohibited until data that may justify their use is available
The biology and ecology of Lake Victoria fishes: their development and management
No full textMany haplochromine cichlids coexisted in Lake Victoria before the upsurge of Nileperch. The introduction of the Nile perch led to depletion of many haplochromines andother fish species in Lake Victoria. The impact of Nile perch predation onhaplochromines differed for different haplochromine trophic groups. Yssichromisfusiformis (G) and Yssichromis laparogramma (G) are among the species that havesurvived in the lake. Yssichromis spp. was studied with the aim of determining theirtrophic role, food and feeding habits. Samples were collected from Bugaia, Buvumachannel and Napoleon Gulf in the northern part of Lake Victoria. The food ofYssichromis spp. varied with size of fish. Both Y fusiformis and Y laparogramma fed onCopepods, Cladocerans, Chaoborus and Chironomids. Juvenile Yssichromis spp. fedexclusively on zooplankton comprising Cyclopoid copepods, Calanoid copepods andCladocera. The relative importance of Chironomid larvae and Calanoid copepods washigher in Bugaia than in Buvuma channel while Cyclopoid copepods and Chironomidpupae were relatively less important in Bugaia. The main food items that Yssichromisspp. fed on in Buvuma channel were Chironomid larvae Cyclopoid copepods,Cladocerans and Calanoid copepods. In Napoleon Gulf, fish caught from commercialfishery of Rastrineobola argentea (P) had fed on Chaoborus and Chironomids. Overall,Yssichromis spp. fed on more zooplankton in Buvuma than in Bugaia. Yssichromis spp.and R. argentea are presently the most abundant zooplanktivores in the northern part ofLake Victoria and are playing an important trophic role as major consumers ofzooplankton and insect larvae in the foodweb of the lake ecosystem. Yssichromis spp. arebridging the transfer of energy from the lower to the higher trophic levels as secondaryconsumers. The fishery is still not contributing to the direct conversion of the primaryproducts, the phytoplankton and detritus that were efficiently utilised by the diversehaplochromine trophic groups that existed before the Nile perch boom.All chapters begin page 1.
On title page: Ugandan version.
Chapter 10
The role of Yssichromis species (Pisces: Cichlidae) in the trophic ecology and foodwebs of Lake Victoria
Full text linkMany haplochromine cichlids coexisted in Lake Victoria before the upsurge of Nile
perch. The introduction of the Nile perch led to depletion of many haplochromines and
other fish species in Lake Victoria. The impact of Nile perch predation on
haplochromines differed for different haplochromine trophic groups. Yssichromis
fusiformis (G) and Yssichromis laparogramma (G) are among the species that have
survived in the lake. Yssichromis spp. was studied with the aim of determining their
trophic role, food and feeding habits. Samples were collected from Bugaia, Buvuma
channel and Napoleon Gulf in the northern part of Lake Victoria. The food of
Yssichromis spp. varied with size of fish. Both Y fusiformis and Y laparogramma fed on
Copepods, Cladocerans, Chaoborus and Chironomids. Juvenile Yssichromis spp. fed
exclusively on zooplankton comprising Cyclopoid copepods, Calanoid copepods and
Cladocera. The relative importance of Chironomid larvae and Calanoid copepods was
higher in Bugaia than in Buvuma channel while Cyclopoid copepods and Chironomid
pupae were relatively less important in Bugaia. The main food items that Yssichromis
spp. fed on in Buvuma channel were Chironomid larvae Cyclopoid copepods,
Cladocerans and Calanoid copepods. In Napoleon Gulf, fish caught from commercial
fishery of Rastrineobola argentea (P) had fed on Chaoborus and Chironomids. Overall,
Yssichromis spp. fed on more zooplankton in Buvuma than in Bugaia. Yssichromis spp.
and R. argentea are presently the most abundant zooplanktivores in the northern part of
Lake Victoria and are playing an important trophic role as major consumers of
zooplankton and insect larvae in the foodweb of the lake ecosystem. Yssichromis spp. are
bridging the transfer of energy from the lower to the higher trophic levels as secondary
consumers. The fishery is still not contributing to the direct conversion of the primary
products, the phytoplankton and detritus that were efficiently utilised by the diverse
haplochromine trophic groups that existed before the Nile perch boom
The biology and ecology of Lake Victoria fishes: their development and management
No full textThe 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).All chapters begin page 1.
On title page: Ugandan version.
Chapter 9
Trophic interrelationships and food-webs among the fishes in ecosystems of the Victoria and Kyoga lake basin
Full text linkThe Victoria and Kyoga lake basins had a high fish species diversity with many fish species
that were found only in these lakes. Two Tilapiines species Oreochromis esculentus and
Oreochromis variabilis were the most important commercial species in these lakes and were
found 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 introduced
species increased, stocks of most of the native species declined rapidly or disappeared
altogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, some
selected 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 the
overall average total number of each species encountered. A trophic consists of species using
the same food category. Shannon-Weaver Index of diversity H (Pielou, 1969) and number of
trophic 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 in
kachera (2)
Report on the current state of the fishery of the Ugandan sector of Lake Albert
No full textFollowing a general outcry by the population riparian to the Ugandan portion of lake Albert about dwindling fish catches, there was concern both from the FAO Country representative in Uganda and the government of Uganda on the state of the fisheries of this lake. The FAO representative accompanied by an official from the Uganda Fisheries and Fish Conservation Association (UFFCA) visitedthe lake in July 1999 (Appendix I). The Ugandan minister of state in charge of the Fisheries sector also visited the lake in November 1999 (Appendix II). The two were in common agreement that the lake was in a stocks crisis and there was need for remedial measures. It was therefore deemed necessary to initiate a technical report updating the present state of the fisheries resources of this lake.An agreement was thus signed between the author and the Food and Agricultural Organization of the United Nations - Sub-Regional Office for Southern Africa inHarare, to undertake this exercise
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