The feeding habit of the CyprinidaeRastrineobola argenteain its new habitat, lakes Bulera and Ruhondo, two Rwandan lakes (Eastern Africa)

Abstract

Key-words:feeding habits, invasive species, Rastrineobola argentea, great lakes, East Africa Rastrineobola argentea Pellegrin 1904, a small pelagic endemic cyprinid from lake Victoria was introduced into lake Bulera (Rwanda) in 1991 in order to develop a fishery. From there, it accidentally colonized lake Ruhondo. To study its biology in its new habitat, samples were collected in 2007 and size and the feeding habits of the fish were analyzed. R. argentea is smaller in lake Bulera (41.8 ± 6 mm) than in lake Ruhondo (mean total body length: 72.6 ± 15 mm). The mean total body length in lake Bulera is less than its size at the first maturity in lake Victoria (47 mm). Differences in size structure of fish between lakes Bulera and Ruhondo is attributed mainly to the food availability in the two lakes. In lake Bulera, the fish feeds on six food items with plant remnants dominant. In lake Ruhondo, R. argentea is a zooplanktivorous feeder like in lake Victoria. The dominant prey is a cladoceran species, Daphnia sp. which has not been observed in lake Bulera during the sampling period. Ruhondo (72,6±15 mm). La longueur moyenne totale du corps dans le lac Bulera est plus petite que sa taille à la première maturité dans le lac Victoria (47 mm). La différence observée entre les deux lacs est attribuable principalement à la disponibilité alimentaire. En effet, dans le lac Bulera, six proies constituent la ration alimentaire de R. argentea avec une dominance de débris végétaux. Dans le lac Ruhondo par contre, R. argentea est zooplanctonophage comme au lac Victoria. La proie dominante est un cladocère, Daphnia sp., qui n'a pas été observé dans le lac Bulera durant la période d'échantillonnage. RÉSUMÉ

Fatty Acid Composition and Levels of Selected Polyunsaturated Fatty Acids in Four Commercial Important Freshwater Fish Species from Lake Victoria, Tanzania

“…After consumption the acids move through the food chain unchanged via zooplankton to fish [ 44 ]. That is why copepods and cladoceran are also rich in EPA [ 45 ]. Adult R. argentea explore the bottom zone during daytime which is the habitat for zooplankton and macrobenthic invertebrates [ 46 ].…”

Microcystin Content in Phytoplankton and in Small Fish from Eutrophic Nyanza Gulf, Lake Victoria, Kenya

“…The surprisingly high proportion of phytoplankton ( Microcystis sp.) in the diet of zooplanktivorous fish may be linked to the general high turbidity in the Gulf system but also has been reported from other systems (e.g., in Rwanda [ 41 ]). Currently, the diet composition and the possible relation to MC content in small fish along the eutrophication gradient in Nyanza Gulf is not known but should be explored further.…”

Water Physico-Chemical Characteristics of the Lakes Burera and Ruhondo, Rwanda

“…1). Lakes Burera and Ruhondo have area of 51.8 and 26.6 Km 2 (Isumbisho et al, 2011) and maximum depths of 179 and 68 m, respectively. Annual rainfall range is between 1400 and 1800 mm/year, and temperature between 10 o C and 25 o C (Musaninkindi, 2013).…”