A study on an herbivorous fish, <i>Oreochromis niloticus</i> L., diet and its quality in two Ethiopian Rift Valley lakes, Awasa and Zwai

Tilahun, Getachew

doi:10.1111/j.1095-8649.1987.tb05767.x

Cited by 63 publications

(48 citation statements)

References 25 publications

(22 reference statements)

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“…This seasonal variability in nutritive characteristics was also observed for O. niloticus in Ziway and the Langano lakes in Ethiopia (Eyualem and Getachew, 1992;Tadesse, 1999). Although the P/E ratio provided by the food ingested by this fish during the dry season is far below that measured in other environments, the digestive yields in proteins and organic matter are nevertheless comparable with those measured for the same species in other Ethiopian lakes (Getachew, 1987(Getachew, , 1993.…”

Section: Discussionsupporting

confidence: 62%

Seasonal effects on the nutritive value of the natural food of three omnivorous fish (Oreochromis niloticus,Sarotherodon galilaeus,Citharinus citharus) in Batamani Pond (Mali, West Africa)

Ble

Arfi

2009

Knowl. Managt. Aquatic Ecosyst.

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Key-words: omnivorous fish, natural food, nutritive value, climate, Batamani Pond, MaliThe chemical composition of the stomach contents and the digestibility of organic matter, proteins and energy of three planktivorous fish species (Oreochromis niloticus, Sarotherodon galilaeus and Citharinus citharus) were studied in Batamani Pond (Mali, West Africa) during the dry and wet seasons. The diet contents of O. niloticus and S. galilaeus presented high levels of organic matter and proteins during the wet season (ashfree dry weight (AFDW): 753 mg·g −1 dw and 703 mg·g −1 dw, protein contents: 479 mg·g −1 AFDW and 449 mg·g −1 AFDW, respectively). In the dry season, the chemical composition of the food was characterized by high proportions of inorganic material (73% and 68% for O. niloticus and S. galilaeus, respectively). The chemical composition of the food of C. citharus was characterized by low seasonal variation. The levels of AFDW (396-461 mg·g −1 dw) and proteins (65-86 mg·g −1 AFDW) in its diet were generally low, reflecting a high proportion of mineral content. During the wet season, the digestibility of AFDW (52% and 58%), total amino acids (68% and 76%) and energy (63% and 56%) increased significantly for O. niloticus and S. galilaeus, respectively. Nutrient and energy digestibility for C. citharus showed no significant seasonal variations (AFDW: 36-45%; total amino acids: 57-64%; energy: 31-39%). The marked seasonal character of the pond, in terms of both hydrology and trophic conditions, had a low impact on the availability and quality of nutritive resources for the two tilapia species O. niloticus and S. galilaeus, while C. citharus appears to have the capacity to adapt its regime to the available food quality, whatever the season.

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Section: Discussionsupporting

confidence: 62%

Seasonal effects on the nutritive value of the natural food of three omnivorous fish (Oreochromis niloticus,Sarotherodon galilaeus,Citharinus citharus) in Batamani Pond (Mali, West Africa)

Ble

Arfi

2009

Knowl. Managt. Aquatic Ecosyst.

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“…At present Ferguson's Gulf is nearly dry (it was completely dry in 1946,1955-56 and 1988) but during periods with high water levels it fills up and becomes one of the most important tilapia fishing grounds in the lake. 0. niluticw is mainly herbivorous (Fish 1955, Lowe-McConnell 1958, Moriarty 1973, Harbott 1976, Getachew 1987) and sheltered areas have a different algal flora compared with the main lake (Rich 1933, Harbott 1982a, Kallqvist et al 1988. They are dominated by rich populations of blue-green algae (cyanobacteria) with a stable production rate exceeding any of those found in the open water.…”

Section: The Ferguson's Gulf Environmentmentioning

confidence: 98%

Population dynamics and life-history styles of Nile tilapia,Oreochromis niloticus, in Ferguson's Gulf, Lake Turkana, Kenya

Kolding

1993

Environ Biol Fish

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SynopsisThree observed dynamic aspects of the Nile tilapia population around Ferguson's Gulf at Lake Turkana, Kenya are evaluated and discussed: the seasonality in catch rates, the enormous inter-annual abundance variations, and the large changes in median size at first maturity. A clear understanding of the regulating mechanisms behind these features has never been achieved, although seasonal changes in the hydrology of shallow sheltered refuges seems to play an important role. This paper suggests a further holistic approach taking the impacts and interrelationships of both the primary productivity and the various predators into account. A synthesizing ecological hypothesis is elaborated, which concludes that most observations on the tilapia dynamics can be explained from changes in the oxygen concentrations and size-specific mortality pressures. Variations in these two proximate factors can ultimately be explained by the floodplain-type fluctuations in the Ferguson's Gulf environment.

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“…Blue-green algae are common components in the diet of 0. niloticus (Fryer & Iles 1972, Moriarty & Moriarty 1973, Trewavas 1983, Getachew 1987. Two species, the filamentous Anabaena cylindrica and a small, twocelled colonial strain of Microcystis aeruginosa, were selected.…”

Section: Introductionmentioning

confidence: 99%

A laboratory investigation of the filtration and ingestion rates of the tilapia,Oreochromis niloticus, feeding on two species of blue-green algae

1991

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Quantitative aspects of the filter-feeding of the tilapia, Oreochromis niloticus, on two species of the blue-green algae -Anabaena cylindrica and Microcystis aeruginosa -were investigated in the laboratory. The ingestion rate of 85mm SL 0. niloticus was best fitted using a linear regression over the range of biovolume concentrations studied (3 x lo6 -3 x lo8 pm3 ml-'). The ingestion rate of 40 mm SL fish gave a curvilinear relationship and was best fitted using a logarithmic regression. For each size class of fish, ingestion rates were higher when fed the larger Anabaena than Microcystis. The results of ingestion and filtration rates are comparable to work on other aquatic suspension feeders and tend to substantiate a universality in the fundamental regulatory mechanism of filter feeding.

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A study on an herbivorous fish, Oreochromis niloticus L., diet and its quality in two Ethiopian Rift Valley lakes, Awasa and Zwai

Cited by 63 publications

References 25 publications

Seasonal effects on the nutritive value of the natural food of three omnivorous fish (Oreochromis niloticus,Sarotherodon galilaeus,Citharinus citharus) in Batamani Pond (Mali, West Africa)

Seasonal effects on the nutritive value of the natural food of three omnivorous fish (Oreochromis niloticus,Sarotherodon galilaeus,Citharinus citharus) in Batamani Pond (Mali, West Africa)

Population dynamics and life-history styles of Nile tilapia,Oreochromis niloticus, in Ferguson's Gulf, Lake Turkana, Kenya

A laboratory investigation of the filtration and ingestion rates of the tilapia,Oreochromis niloticus, feeding on two species of blue-green algae

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