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The role of the freshwater shrimp Caridina nilotica 

(Roux) in the diet of the major commercial fish species 

in Lake Victoria, Tanzania 

Y. L. Budeba ab ; I. G. Cowx c 

a Tanzania Fisheries Research Institute, Kyela, Tanzania 

b TAFIRI, Dar-es-Salaam, Tanzania 

c Hull International Fisheries Institute, University of Hull, England 

Online Publication Date: 01 October 2007 

To cite this Article: Budeba, Y. L. and Cowx, I. G. (2007) 'The role of the freshwater 

shrimp Caridina nilotica (Roux) in the diet of the major commercial fish species in 

Lake Victoria, Tanzania', Aquatic Ecosystem Health & Management, 10:4, 368 - 380 

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The role of the freshwater shrimp Caridina nilotica 

(Roux) in the diet of the major commercial fish species 

in Lake Victoria, Tanzania 

Y. L. Budeba 1† and I. G. Cowx 2∗ 

1 Tanzania Fisheries Research Institute,P.O. Box 98 Kyela, Tanzania. 

2 Hull International Fisheries Institute, University of Hull HU6 7RX, England 

† Current address: TAFIRI, Dar-es-Salaam, Tanzania 

∗ Corresponding author: i.g.cowx@hull.ac.uk 

The major commercial fish species of Lake Victoria at the present time are Lates niloticus, Oreochromis 

niloticus and Rastrineobola argentea. The contribution of Caridina nilotica in their diet was studied in 

the Tanzanian waters of Lake Victoria between March, 1999 and January, 2002. Stomach samples were 

collected during routine bottom trawl surveys in Tanzania. The results show that haplochromines dominate 

the diet of Nile perch, followed by C. nilotica, R. argentea, juvenile Nile perch, fish remains and other 

prey. Caridina nilotica predominance in diets decreased as size of the Nile perch increased, as this species 

switched to haplochromines. Larger perch also feed on their own juveniles. The importance of C. nilotica 

in the diet of L. niloticus wasrelatively greater in deeper water than that in shallower stations. 

The diet of O. niloticus was predominantly algae followed by C. nilotica, dagaa, Chaoborus, Odonata 

and others. O. niloticus has shifted its diet from strictly herbivory to a more omnivorous diet, feeding 

opportunistically on the most available food material. 

The overall diet of R. argentea waspredominantly copepods, followed by Chaoborus, Cladocera, C. nilotica, 

Chironomids and insects. In the present food web, C. nilotica is an important food source for the fish 

stocks of Lake Victoria. The sustainability of the fisheries of Lake Victoria depends among other things on 

the abundance and availability of C. nilotica. 

Keywords: Feeding habits, Nile perch, Nile tilapia, dagaa 

Introduction 

Currently, the main commercial fish species of 

Lake Victoria are Lates niloticus, Oreochromis 

niloticus, Rastrineobola argentea and the haplochromine 

cichlids (Budeba, 2003). The diet of 

L. niloticus has been the subject of many detailed 

studies (Ligtvoet and Mkumbo, 1990; Mkumbo 

and Ligtvoet, 1992; Ogutu Ohwayo, 1985, 1990a, 

1990b; Hughes, 1986; Ogari and Dadzie, 1988; 

Owili, 1999). Their results indicate that its food 

preference has changed from haplochromine cichlids 

to C. nilotica, R. argentea, juvenile L. niloticus 

and insects. In the research undertaken so far, the 

importance of C. nilotica in the diet of the main 

fish species has received little attention (Budeba, 

2003). 

The objective of this paper is to assess the spatial 

and temporal importance of C. nilotica in the 

diet of various size classes of the major commercial 

fish species in the Tanzanian waters of Lake 

Victoria. 

368 

Aquatic Ecosystem Health & Management, 10(4):368–380, 2007. Copyright C○ 2007 AEHMS. ISSN: 1463-4988 print / 1539-4077 online 

DOI: 10.1080/14634980701703876

Budeba and Cowx / Aquatic Ecosystem Health and Management 10 (2007) 368–380 369 


Materials and methods 

Study area 

The Tanzanian part of Lake Victoria is usually divided 

into three sampling zones (A, B, C) (Figure 1). 

Zone A stretches from Kome and Buhiru islands in 

the southwest, and northeastwards to the south west 

of Ukerewe island, including the Speke and Mwanza 

Gulfs. Zone B starts from the Tanzania-Kenya border 

southwards to the north west of Ukerewe Island. 

Zone C covers the Kagera waters from Rubafu Bay 

on the Tanzania-Uganda border southwards to Kome 

Island, including the Emin Pasha Gulf. These three 

zones were sampled over 14-day periods, on a quarterly 

basis. 

Sampling programme 

The diet study was conducted between March, 

1999 and January, 2002. Fish stomachs were collected 

during routine quarterly bottom trawl surveys 

in each of the three sampling zones. Trawling was 

done during the daytime for a period of fourteen 

days per area per month, using RV Lake Victoria Explorer, 

(length 17 m; 250 H.P.). The catch was sorted 

into commercial categories. Depending on the size 

of the catch, from one or two hauls, specimens of 

Nile perch, Nile tilapia, dagaa and haplochromines 

were dissected on a daily basis for sex/maturity 

and dietary analysis. Entire guts were removed and 

individual stomachs examined separately. For the 

stomach analysis, the points method (Hynes, 1950; 

Figure 1. Map of Lake Victoria with the sampling zones of the Tanzanian sector.


370 Budeba and Cowx / Aquatic Ecosystem Health and Management 10 (2007) 368–380 

Figure 2. Monthly composition of the diet of Lates niloticus, March 1999–January 2002 (sample sizes are shown on top of the bars). 

Hyslop, 1980) was used to determine the contribution 

of each prey item to the diet (Figure 2). The 

food items were identified to the generic level and 

awarded points proportional to the total number of 

points awarded to the stomach. Stomach fullness 

was noted before opening the gut. Each stomach was 

awarded an index of fullness ranging from 0 (empty) 

to 1 (full). The contribution of each prey item was estimated 

as a fraction of the fullness in decimal points. 

To determine changes in diet with size, the points 

awarded to each prey type were summed within each 

10 cm length category. Monthly geographical variations 

in the diet were similarly assessed. 

R. argentea has no distinct stomach. Its Z-shaped 

intestine forms three equal loops in the body cavity 

(Wanink, 1998). Of these, only the anterior loop was 

removed and its content flushed into a Petri dish 

which was then examined under a low-power stereo 

microscope. 

In order to assess the temporal and spatial variations 

in the diets of all species, data from each zone 

were grouped by month. Within each zone, the data



Figure 3. Composition of the diet of different length groups of Lates niloticus, March 1999–January 2002. 

were also grouped into depth ranges. For practical 

purposes, L. niloticus were grouped into 10 cm size 

classes. 

Results 

Lates niloticus 

A total of 4263 stomachs of L. niloticus were 

examined. This species feeds on a wide variety of 

organisms, 18 of which were identified. They can be 

divided into haplochromines (47.8%), C. nilotica 

(38.6%), dagaa (7.5%), juvenile Nile perch (2.3%), 

fish remains (2.0%) and other prey items (2.5%). C. 

nilotica showed consistent seasonal variation in all 

three zones (Figure 2). 

In zone A, the overall diet of Nile perch was 

predominantly haplochromines (60.2%), followed 

by C. nilotica (29.2%), dagaa (4.0%), juvenile Nile 

perch (1.6%), fish remains (1.8%) and unidentified 

other items (3.4%). In zone B, C. nilotica (53.6%) 

dominated, followed by haplochromines (35.6%), 

dagaa (8.5%), juvenile Nile perch (3.7%), fish remains 

(0.8%) and other items (1.8%). In zone C, 

C. nilotica dominated as well (42.6%), followed by



Figure 4. Diet of Lates niloticus by water depth, March 1999–January 2002. 

haplochromines (27.5%), dagaa (13.8%), juvenile 

perch (2.5%), fish remains (3.7%), and other items 

(1.7%). C. nilotica was more important during the 

dry season (June – September); when they were absent, 

haplochromines formed the alternative food for 

the Nile perch. 

Changes in diet with size of Nile perch differed 

between zones (Figure 3). Diets of fish below 20 cm 

TL were always dominated by C. nilotica. Juveniles 

of its own species contributed only 14% in stomachs 

above 100 cm TL in zone A, against 61.5% in zone 

B and 80% in zone C. 

There was marked variation in the contribution 

of C. nilotica to the diet of Lates niloticus with depth 

(Figure 4). At depths below 10 m in zone A, haplochromines 

predominated, followed respectively by 

C. nilotica, dagaa and juvenile Nile perch. 

Oreochromis niloticus 

A total of 616 stomachs of O. niloticus were examined. 

Its diet was predominantly algae (65.0%), 

C. nilotica (17.0%), dagaa (8.5%), Chaoborus 

(5.3%), Odonata (1.5%) and others (2.8%). The 

latter component was made up of bivalves, plant



Figure 5. Monthly composition of the diet of Oreochromis niloticus, June 1999–January 2002. 

material, shells, oligochaeta, haplochromines, Barbus, 

and zooplankton. The diet showed temporal and 

spatial variations over the study period (Figure 5). 

There was a slight increase in the contribution of C. 

nilotica with increased predator length (Figure 6). 

In the 1–10 m depth range, the diet of O. niloticus 

consisted of algae (65.3%), C. nilotica (15.7%), 

dagaa (9.1%) and Chaoborus (5.6%). At 11–20 m 

depths, the diet was predominantly algae (71.9%) 

and C. nilotica (20.8%). Three items dominated 

the food at 21-30 m depth: algae (38.9%), C. 

nilotica (34.9%) and dagaa (16.7%). The contribution 

of C. nilotica to the diet increased from 

shallow to deep-water stations, as algae decreased 

(Figure 7). 

Rastrineobola argentea 

A total of 638 stomachs of R. argentea were examined. 

The overall diet was composed of copepods 

(36.1%), Chaoborus (30.8%), Cladocera (17.0%), 

C. nilotica (11.4%), Chironomid larvae (4.6%) and 

insects (2.6%). The contribution of C. nilotica fluctuated 

per month, but generally in low proportions 

(Figure 8). C. nilotica occurrence was relatively 

higher in stomachs of larger fishes in each of the 

three sampling areas (Figure 9). Diet composition 

varied little with water depth (Figure 10). Copepoda, 

Chaoborus, Cladocera and C. nilotica were 

the main items caught at all depths. The contribution 

of C. nilotica was relatively higher in the deep 

and offshore water stations than in the shallow and 

inshore water stations (Figure 10). 

Discussion 

Diet and feeding pattern of Nile perch 

Nile perch was introduced in Lake Victoria 

in 1954 (Fryer, 1960). At first, it was predominantly 

feeding on haplochromines, which were the 

most abundant species (Gee, 1964, Hamblyn, 1966; 

Okedi, 1971). Kudhongania and Cordone (1974) 

reported 83% of the ichthyomass to be of haplochromine 

cichlids. The abundance of Caridina 

nilotica stocks was low at the time, and it was consumed 

mainly by Schilbe, Mormyrus, Barbus and 

Brycinus (Corbet, 1961). After the L. niloticus boom 

in the Mwanza Gulf, which started in 1983, the haplochromine 

cichlids virtually disappeared (Witte et 

al., 1992) and by 1986 large quantities of C. nilotica 

were observed. 

C. nilotica was reported to be an important prey 

for L. niloticus in Lakes Albert and Turkana where 

L. niloticus is endemic (Hamblyn, 1966; Gee, 1969), 

and contributes significantly to the diet of L. niloticus 

in Lake Chad (Hopson, 1972). 

Lates niloticus, being an opportunistic predator, 

quickly adapted its feeding habits, starting 

with zooplankton and then switching to insects, 

C. nilotica and finally to fish (Ogari and 

Dadzie, 1988; Ligtvoet and Mkumbo, 1990; Ogutu- 

Ohwayo, 1990a, 1990b; Mkumbo and Ligtvoet, 

1992; Hughes, 1992; Mkumbo et al. 1996; Lowe- 

McConnell, 1997; Agullo, 1999; Owili, 1999). 

Owili (1999) reported that zooplankton is important 

in the diet of L. niloticus of 1–3 cm TL and 

that C. nilotica becomes dominant from 4 cm TL 

onwards. Ogari and Dadzie (1988) reported that



Figure 6. Composition of the diet of different size groups of Oreochromis niloticus. 

zooplankton, and especially Cladocerans, Chironomids, 

Copepods and Povilla adusta comprised the 

food of L. niloticus below 5 cm TL. As very small 

fish were not present in the trawl samples, no zooplankton 

was found in L. niloticus stomachs. The 

dominance of juvenile Nile perch in the catches 

(Mkumbo and Ezekiel, 1999; Mkumbo et al., 2005; 

Mkumbo, 2002; Mkumbo et al., 2002) reflects their 

availability as prey for the larger Nile perch. 

Over the past three decades the abundance of C. 

nilotica in Lake Victoria has increased tremendously 

(Budeba, 2003). The present study shows that C. 

nilotica has become the dominant prey for L. niloticus 

especially for fish up to 60 cm TL (Figure 2). 

The present dominance of haplochromine cichlids 

in the stomachs of L. niloticus above 60 cm 

TL reflects the recovery of the haplochromine cichlids 

and the return to their former role when they 

were the most abundant species in the lake. They 

formed an important by-catch in the dagaa catches 

at Igombe beach (Budeba, 2003). From 1991 on, 

Seehausen et al. (1997) reported a recovery of the 

zooplanktivores Yssichromis pyrrhocephalus and Y. 

laparogramma in the Mwanza Gulf. In Speke Gulf,



Figure 7. Diet composition of Oreochromis niloticus by water depth, June 1999–January 2002. 

Witte et al. (2000) reported that Y. laparogramma 

comprised 64% of the weight of the catch of the lift 

net fishery targeting dagaa, while 33% consisted of 

R. argentea and 3% of juvenile Nile perch. 

Fish may switch to other prey in response to 

changes in their relative abundance (Murdoch and 

Oaten, 1975). In Zone A, Nile perch feed mostly on 

haplochromines, which appear to be more abundant 

(Witte et al., 2000; Budeba, 2003), while in zones B 

and C where haplochromine abundance appears to 

be low, they feed predominantly on C. nilotica. The 

size range of L. niloticus feeding mostly on C. nilotica 

appears to have increased from 1–50 cm TL in 

the past to 60 cm TL at present. This change in food 

selection with increased predator size is in agreement 

with the findings of Ogari and Dadzie (1988) 

in the Kenyan waters of Lake Victoria and Hamblyn 

(1966) in Lake Albert, who found that invertebrates 

dominated in the stomachs of L. niloticus below 60 

cm TL, and that fish above 60 cm TL were piscivorous. 

The majority of L. niloticus caught in the 

Tanzanian waters of Lake Victoria were 5–45 cm 

TL in size (Mkumbo and Ezekiel, 1999; Mkumbo 

et al., 2005; Mkumbo et al., 2002). The whole Nile 

perch stock therefore predominantly feeds on C. 

nilotica. 

Figure 8. Composition of the diet of Rastrineobola argentea July 1999–September 2001.



Figure 9. Prey items in the diet of Rastrineobola argentea by size group, June 1999 to September 2001. 

Diet and feeding pattern of Nile tilapia 

Oreochromis niloticus, which used to be a strictly 

herbivorous fish feeding on a variety of algae and 

higher plant materials, has diversified its diet to C. 

nilotica, zooplankton, R. argentea and Chaoborus 

larvae. This confirms the trophic plasticity of the 

species (Lowe-McConnell, 1958). The switch from 

a strictly herbivorous to a more generalist diet reflects 

the ecological changes that have occurred in 

the lake. The anaerobic environment in Lake Victoria 

favoured the flourishing of C. nilotica and 

other micro-invertebrates (Hecky, 1993; Mwebaza- 

Ndawula, 1998; Mwebaza-Ndawula et al., 1999; 

Budeba, 2003). In the present study, blue-green algae, 

green algae and diatoms formed the dominant 

food of O. niloticus. The relative contribution of C. 

nilotica was, however, also important. O. niloticus is 

a shallow water fish, which prefers to live in aquatic 

macrophytes like papyrus (Cyperus papyrus), lake 

bottom grass-beds and even underneath the water



Figure 10. Prey items in the diet of Rastrineobola argentea by water depth. 

hyacinth Eichhornia crassipes mat. The same areas 

are used by C. nilotica as feeding grounds as 

well as nursery habitats. It is probable that this habitat 

overlap is responsible for the feeding relationship 

between these organisms. In Ugandan waters, 

Balirwa (1998) reported detritus and insects, especially 

chironomid larvae to be the most important 

food items of O. niloticus. Njiru (1999) found insects 

as the dominant food of O. niloticus followed 

by algae, fish, higher plant material, zooplankton, 

C. nilotica, bivalves and oligochaeta in the Kenyan 

part of the lake. On the other hand, Owili (1999) 

reported phytoplankton and zooplankton to be the 

most important food items in the Kenyan waters but 

this was for fish below 10 cm in length. 

The present study indicated seasonal variations 

in the contribution of C. nilotica to the diet of O. 

niloticus (Figure 5). These may reflect variations in 

the abundance of both C. nilotica (Budeba, 2003) 

and its zooplankton food in the lake (Wanink, 1989, 

1998; Mwebaza-Ndawula, 1998). In the dry season, 

Caridina nilotica tends to migrate away from the 

shallow inshore waters to the deep offshore waters to 

breed and comes back during rainy season (Budeba, 

2003). Sample sizes in some months are rather 

small. 

The introduction of O. niloticus in 1961 (then 

restricted to very shallow littoral waters) caused a 

strong competition for food with the phytoplanktivorous 

haplochromines (Moreau et al., 1993). A 

wider food spectrum is one of the factors which enabled 

O. niloticus to be successful in Lake Victoria 

(Fryer and Iles, 1972). 

Diet of Rastrineobola argentea 

Although Rastrineobola argentea is one of the 

most important prey items of L. niloticus, itmanages 

to co-exist with it in Lake Victoria, even in 

the absence of haplochromines cichlids. R. argentea 

has replaced the zooplanktivorous haplochromines 

cichlids in Lake Victoria (Goldschmidt et al., 1993). 

In the daytime, R. argentea feed on zooplankton, 

which concentrates near the bottom of the lake. 

They migrate to the surface at night. The zooplankton 

community of Lake Victoria is dominated 

by cyclopoid copepods (Branstrator et al., 1996; 

Mwebaze-Ndawula, 1998; Wanink, 1998; Omondi, 

1999; Owili, 1999; Budeba, TAFIRI, Dar-es-Salaam 

personal observations). During the nights, with 

many emerging Chaoborus and chironomids at the 

surface, R. argentea catches these insects (Wanink 

et al., 1989). In the dry season, zooplankton and C. 

nilotica tend to migrate for breeding from the shallow 

inshore waters to deep offshore waters. In case 

of oxygen depletion in the lower water column, adult 

R. argentea concentrate just above the deoxygenated 

layer during the daytime (Wanink, 1998). The same 

area is occupied by C. nilotica during thermal stratification 

(Budeba, 2003). 

The present study identified six food items of 

R. argentea, i.e. C. nilotica, Cladocera, Copepoda, 

Chaoborus, insects and chironomids. These results 

are in agreement with Wanink (1988, 1989, 1998) 

and Hoogenboezem (1985) in the Mwanza Gulf of 

Lake Victoria, but differ somewhat from Kenyan 

and Ugandan parts of Lake Victoria. Owili (1999) 

reported the dominance of Cladocera and absence



of C. nilotica in the diet of R. argentea in Kenyan 

waters of Lake Victoria. Mwebaza-Ndawula (1998) 

reported the absence of C. nilotica in the stomachs 

of R. argentea in the northern part of Lake Victoria. 

The contribution of C. nilotica to the diet of R. 

argentea shows seasonal variation without defined 

trend. This can be attributed both to the seasonal 

fluctuations in R. argentea abundance as reflected 

in the commercial catches (Budeba, 2003), and to 

seasonal variations in the abundance and availability 

of its key food C. nilotica and other macroinvertebrates. 

The contribution of C. nilotica to the diet of R. 

argentea was found to increase with fish size. Juvenile 

R. argentea hide in shallow waters, especially in 

aquatic weeds such as water hyacinth (E. crassipes), 

papyrus (C. papyrus), and Ceratophyllum; feeding 

on insects, which are more abundant there. As the 

fish increase in size, C. nilotica and Chaoborus become 

important as food. Later, R. argentea becomes 

truly pelagic and moves offshore. Even here, it tends 

to hide near the bottom in the daytime and comes to 

the surface at night. C. nilotica shows exactly these 

same diel migrations. 

In order to assess the possible impact of prey 

switching on dagaa, Wanink (1998) established the 

energy content of different prey types in function 

of their size. He observed that stomachs filled with 

prawns contain 15 times more energy than those 

with zooplankton. The energy content of C. nilotica 

is 20.34 J mg −1 for unberried and 28.01 J mg −1 for 

berried ones (Hart, 1981; Wanink, 1998; Budeba, 

2003). 

Conclusions 

In the present food web, C. nilotica is an important 

food source for the fish stocks of Lake Victoria. 

Therefore the fisheries of Lake Victoria, and their 

sustainability, depends among other things, on the 

abundance and availability of C. nilotica in the lake. 

Acknowledgements 

This paper formed part of Yohana Budeba’s PhD 

research on the role of Caridina nilotica in the Lake 

Victoria fisheries, Tanzanian waters. We express our 

sincere thanks to the European Union for funding 

this study through the Lake Victoria Fisheries Research 

Project II. We thank the Director General of 

TAFIRI for institutional support. Thanks also go 

to the crew members of RV Victoria Explorer for 

data collection, handling and analysis and to my collegues 

for moral support during this study. 

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