Spatial distribution and temporal changes in the fish populations of Lake Victoria

Getabu, Albert

doi:10.1016/s0990-7440(03)00008-1

Cited by 65 publications

(55 citation statements)

References 16 publications

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“…Temperature most likely affected densities indirectly through high recruitment and juvenile survival during the warmer, productive, wet seasons in the Mwanza Gulf. This seasonal effect of temperature on small Nile perch only, and the non-linear, positive nature of the relationship might be the reason why other studies found contrasting results with regard to the relationship between temperature and Nile perch densities (Getabu et al, 2003;Goudswaard et al, 2011;Nyboer & Chapman, 2013).…”

Section: Factors Determining Nile Perch Distributionsmentioning

confidence: 84%

“…Since the start of the fisheries concerns have been voiced that Nile perch stocks are declining and may collapse if fishing pressure will continue to increase (Mkumbo, 2002;Balirwa et al, 2003;Getabu et al, 2003;Ogutu-Ohwayo, 2004;Matsuishi et al, 2006;Mkumbo et al, 2007). However, stock assessments based on Nile perch catches and population size structure showed no signs of overfishing or long-term decline of the Nile perch stock, although, since the 1990s the stock shows short-term decadal fluctuations (Kolding et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…For instance, Getabu et al (2003) observed high Nile perch densities in warmer, shallow waters. However, other studies observed a negative or no relationship between Nile perch densities and water temperature (Goudswaard et al, 2011;Nyboer & Chapman, 2013;TaabuMunyaho et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Most studies on the Nile perch stock in Lake Victoria focussed on whole lake dynamics over long periods and on the impacts of the Nile perch fisheries (Mkumbo, 2002;Getabu et al, 2003;Mkumbo et al, 2007). In addition, Nile perch distribution was generally studied in open waters of more than 15 m depth where most of the commercial Nile perch fishery is concentrated (Mkumbo, 2002;Getabu et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, Nile perch distribution was generally studied in open waters of more than 15 m depth where most of the commercial Nile perch fishery is concentrated (Mkumbo, 2002;Getabu et al, 2003). Little is known about how changes in abiotic factors as for instance caused by eutrophication or climate change will affect the Nile perch stock and at what scales such effects will become apparent.…”

Section: Introductionmentioning

confidence: 99%

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Nile perch distribution in south-east Lake Victoria is more strongly driven by abiotic factors, than by prey densities

et al. 2015

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We studied the effects of environmental driving factors (maximum depth, visibility, oxygen, temperature, and prey densities) on the distribution and diet composition of Nile perch (Lates niloticus) in south-east Lake Victoria from 2009 to 2011. We tested the hypotheses that (i) Nile perch distribution is regulated by the same environmental factors on a local scale (Mwanza Gulf) and on a regional scale (Mwanza Gulf, Speke Gulf and the open lake in Sengerema district), and (ii) driving factors act differently on different Nile perch size classes. Fish were sampled with gillnets. Nile perch densities were highest in the shallow part of the Mwanza Gulf and during the wet seasons, mainly caused by high densities of juveniles. The environmental driving factors explained Nile perch distributions on both regional and local scales in a similar way, often showing non-linear relationships. Maximum depth and temperature were the best predictors of Nile perch densities. Prey densities of shrimp and haplochromines did not strongly affect Nile perch distributions, but did explain Nile perch diet on a local and regional scale. We conclude that abiotic variables drive Nile perch distributions more strongly than prey densities and that feeding takes place opportunistically.

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Section: Factors Determining Nile Perch Distributionsmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Nile perch distribution in south-east Lake Victoria is more strongly driven by abiotic factors, than by prey densities

et al. 2015

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References

2005

Fisheries Acoustics

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The Environment of Lake Victoria (East Africa): Current Status and Historical Changes

Sitoki

Gichuki

Ezekiel

et al. 2010

International Review of Hydrobiology

129

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Beginning in the mid-1980s Lake Victoria experienced severe eutrophication and it was suggested that deteriorating water quality might lead to a collapse of its fisheries. A series of lake-wide surveys carried out 1999-2001 and 2005-2009 revealed that the temperature of the lake had risen by > 1 °C since 1927, with more rapid warming of the deeper waters reducing the thermal gradient in the water column and thus weakening stratification and the extent and severity of deoxygenation. The chlorophyll a concentrations in open water decreased since the 1980s, while Secchi disc visibility increased, indicating a reduced severity of algal blooms. Chlorophyll a was higher and Secchi disc visibility lower in inshore waters but there has been no deterioration in these areas since the 1980s. The conductivity remained unchanged, although it was about 50% greater in the semi-enclosed Nyanza Gulf than in the open lake. The water quality of the lake has therefore improved considerably despite the fact than concentrations of plant nutrients have not decreased and the reasons why this may be the case are discussed. IntroductionLake Victoria is the world's second largest freshwater lake (area = 68,800 km 2 , mean depth = 35 m) and it supports one of the world's largest inland fisheries, yielding almost one million tons per annum (LVFO, 2009a). It has attracted much interest in recent years because of the extraordinary ecological changes that occurred in it over the last three decades, comparable in their magnitude to those in newly created man-made lakes. These changes were triggered in the mid-1980s by an introduced predatory fish, the Nile perch Lates niloticus (L.), and its subsequent destruction of the endemic haplochromine cichlids. These fishes, which formed a species flock with some 500 described forms (WITTE et al., 2007), accounted for over 80% of the fish biomass in the lake (KUDHONGANIA and CORDONE, 1974) but they were small fish thought to be of little commercial value. Nile perch were therefore introduced with the specific intention of converting haplochromines into a more * Corresponding author 210 L. SITOKI et al.

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Spatial distribution and temporal changes in the fish populations of Lake Victoria

Cited by 65 publications

References 16 publications

Nile perch distribution in south-east Lake Victoria is more strongly driven by abiotic factors, than by prey densities

Nile perch distribution in south-east Lake Victoria is more strongly driven by abiotic factors, than by prey densities

References

The Environment of Lake Victoria (East Africa): Current Status and Historical Changes

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