1,720,990 research outputs found
Addis Ababa declaration on Enset
No full textThe “International Workshop on Enset (Ensete ventricosum) for Sustainable Development: Current research trends, gaps and future direction for a coordinated multidisciplinary approach in Ethiopia” has taken place between October 17 and 18, 2016
Long-term changes in phyto- and zooplankton communities of Lake Hawassa, Ethiopia
No full textWe studied phyto- and zooplankton communities of Lake Hawassa (or Awassa) between November 2003 and August 2004, and compared findings with historical data since the 1980s to assess potential inter-decadal changes. The lake is located in the Ethiopian Rift Valley in the vicinity of the growing city Hawassa which receives adverse effluents from textile and ceramics industry and municipal sewage apparently with little treatment. In 2003/04, phytoplankton abundance comprised 54% Chlorophyta, 26% cyanoprokaryotes, 18% diatoms and 2% others, a proportion similar to previous records. However, the mean phytoplankton biomass in terms of chlorophyll a (19 μg L-1) was lower than reported from previous studies but similar to a report in 2010. In contrary, areal rate of gross photosynthesis had increased in the last two decades with higher values recorded in 2003-04 (0.35 to 2.21 g O2 m-2 h-1). Even though zooplankton community composition remained the same, the abundance and dominance of taxa had changed in the last decades. In 2003/04, the mean abundance of cyclopoid-copepods was 58 000 ± 9200 (SE) Indl m-3 whereas cladocera abundance (2 600 ± 640 SE Indl m-3 was very low in the lake. Rotifers outnumbered other zooplankton with a maximum value of 264 000 Indl m-3, which was about five times greater than previous reports. Adult cyclopoid to nauplii ratio of 0.27 in 2003-04 study was indicative that cannibalism had diminished, probably due to increased rotifers as prey, which contradicted a previous hypothesis. Despite its closed nature, the plankton of Lake Hawassa changed erratically during a decade, probably due to intense biological interactions in the system.Key words/phrases: Decadal change, Interactions, Rift valley, Phytoplankton, Zooplankton
Feeding habits, ontogenetic dietary shift and some aspects of reproduction of the tigerfish hydrocynus forskahlii (Cuvier, 1819) (Pisces: Characidae) in Lake Chamo, Ethiopia
No full textThe diet composition, ontogenetic dietary shifts and reproduction of the tigerfish Hydrocynus forskahlii (Cuvier, 1819) were studied from 386 fish samples (11.2 cm-69.6 cm total length, TL) collected from Lake Chamo from January to August 2005. From the total number of fish samples 231 (59.8%) that contained food in their stomachs were used in the analysis. Zooplankton occurred in 35.8% of the stomachs examined, accounted for 78.8% numerically and constituted 10.3% volumetrically. Insects occurred in 58.5% of the stomachs examined, constituted 20.8% of the total number of prey organisms and accounted for 38.7% of the total volume of the food items. Tilapia fry occurred in 43.4% of the stomachs examined, constituted 0.73% of the total number and 50.3% of the total volume of the prey. Macrophytes occurred in 18.9% of the stomachs and accounted for 0.74% of the total volume. H. forskahlii fed mainly on zooplankton when young and shifted to piscivorous feeding habit when it attained the size of about 25 cm TL. The sex ratio was significantly different from unity where 306 (79.3%) females and 80 (20.7%) males were caught during the sampling period. Relative fecundity of H. forskahlii ranged between 135 and 204, while mean fecundity ranged between 35,564 and 411,810. The relationships between fecundity (F) and TL (F = 0.0184TL4.08, r2 = 0.61) and F and total weight (TW) (F = 36.89TW1.23, r2 = 0.70) were curvilinear while the relationship between F and ovary weight (OW) (F = 4082.9OW 7949.5, r2 = 0.88) was linear.Keywords/phrases: Diet composition, H. forskahlii, Lake Chamo, ReproductionEthiop. J. Biol. Sci., 7(2): 123-137, 200
FOOD AND FEEDING HABITS OF THE CATFISH, BAGRUS DOCMAK (FORSSKAL, 1775) (PISCES:BAGRIDAE) IN LAKE CHAMO, ETHIOPIA
Get PDFThe natural food of the catfish Bagrus docmak was studiedfrom February -1995 to February 1996 in Lake Chama, Ethiopia. Thestomach contents. of a total of 534 fish samples, ranging in size £rom 33-99 cm fork length (LF) and 500-17400 g in tOtal weight (WT) wereinvestigated. The diet of B. docmak was composed of ins~ (larvae,nymphs and adults), aquatic snails and different fish species such asSynodontis schall, Labeo horie, Oreochromis. niloticus, Barbus sp. andHydrocynus forskalii. Juvenile B. docmak « 40 em LF) ingested more insects than fish while older fish were largely piscivorous, with fish constituting more than 98% of their diet by weight. S. schall was the most important prey and occurred in more than 81 % of all the stomachs of large B. docmak. The prey:predator (S. schall:B. docmak) length ratio varied between 1:2 and 1:6. The feeding habit of B. docmak in Lake Chama is compared with that of other tropical African lakes that have similar ichthyofauna
Food and feeding habits of the catfish, Bagrus docmak (Forsskal, 1775) (Pisces:Bagridae) in Lake Chamo, Ethiopia
No full textThe natural food of the catfish Bagrus docmak was studied from February 1995 to February 1996 in Lake Chamo, Ethiopia. The stomach contents of a total of 534 fish samples, ranging in size from 33—99 cm fork length (LF) and 500—17400 g in total weight (WT) were investigated. The diet of B. docmak was composed of insects (larvae, nymphs and adults), aquatic snails and different fish species such as Synodontis schall, Labeo horie, Oreochromis niloticus, Barbus sp. and Hydrocynus forskalii. Juvenile B. docmak (< 40 cm LF) ingested more insects than fish while older fish were largely piscivorous, with fish constituting more than 98% of their diet by weight. S. schall was the most important prey and occurred in more than 81% of all the stomachs of large B. docmak. The prey:predator (S. schall:B. docmak) length ratio varied between 1:2 and 1:6. The feeding habit of B. docmak in Lake Chamo is compared with that of other tropical African lakes that have similar ichthyofauna. SINET: Ethiopian Journal of Science Volume 24, No. 2 (December 2001), pp. 239-254
Key words/phrases: Bagrus docmak, Ethiopia, Lake Chamo, prey:predator ratio, Synodontis schal
Major Factors that Structure the Benthic Fauna of a Shallow, Tropical Lake, Lake Kuriftu, Ethiopia
No full textThe aim of this study was to determine the communitystructure of the benthos in Lake Kuriftu in relation to some environmentalvariables. Benthic samples were collected with an Ekman grab (0.0225 m2)from three sites (littoral, sub-littoral and profundal zones) on a monthly basisfrom September 2009 to February 2010. Dissolved oxygen and temperaturewere measured with a probe at different depths of each site. Sediment texturewas determined by the Bouyoucos hydrometer and organic matter content byloss on ignition method. Chironomids, EPT (Ephemeroptera, Plecoptera,Trichoptera), oligochaetes and coleopterans were abundant in littoral andsub-littoral zones, with EPT much higher in the vegetated littoral area. Themean density of benthic macro-invertebrates in littoral, sub-littoral andprofundal zones was 20,443, 18,251, and 4,388 ind/m2, and that ofChironomids was 12,545, 14,003 and 3,215 ind/m2, respectively. Theprofundal zone had the lowest diversity with abundant oligochaetes but noEPT samples, despite the high oxygen content of the profundal zone (6.33mg/l). Chironomids and oligochaetes were present in all zones which hadnegligible difference in dissolved oxygen and organic matter content. Thelittoral zone had highest diversity (H’=1.26) and richness (d=2.72). Ourresults indicate that abundance of benthic macro-invertebrates of LakeKuriftu was best correlated with the presence of vegetation in the littoral zoneand sediment texture (high clay) in the littoral and profundal zones. Weconclude that benthic macro-invertebrate community structure in LakeKuriftu is mainly influenced by spatial variation in vegetation, sedimenttexture and temperature, but not dissolved oxygen and organic matterconten
Evaluation of multi-assemblage metrics and temperate indices as indicators of human impact in Lake Ziway, Ethiopia
No full textLake bioassessment is routinely done using one biological community such as macro-invertebrates, diatoms, macrophytes or fish. Theuse of at least two assemblages has been suggested as they are believed to be more robust indicators, because each community responds differently to potential stressors in waters. This study aimed to use macroinvertebrate and diatom assemblages to identify metrics and temperate indices that could discriminate between reference and impacted sites of the littoral zone of Lake Ziway, Ethiopia. The Lake Habitat Quality Assessment (LHQA) method was used to categorize the sites in the littoral zone of the lake. Lake water, macroinvertebrate, and diatom samples were collected from 3 reference and 6 impacted sites between September 2015 and April 2016 with standard methods and following the Ontario Benthos Biomonitoring Protocol. A total of 34 macroinvertebrate taxa and 39 diatom species were recorded. 32 macroinvertebrate and 18 diatom indices were tested for their ability to discriminate between the reference, intermediate and multiple-stressed sites using correlations between metrics, similarity values with SIMPER and boxplots overlaps. Further, correlation of the metrics with physico-chemical parameters extracted metrics and indices with high discrimination efficiency(≥3). The indices remaining were 5 macroinvertebrate (NT, PTI, PETI, PDT and CLI) and 4 diatom (CEE, PTV, TDI, and IBD) indicators which clearly discriminated between the impacted (intermediate and multiple stressors) and reference sites, but not within the impacted sites, in the lake. These data can also possibly serve as core metrics for multi-assemblage index development for this shallow, tropical lake.
Key words/phrases: Diatom, Discriminatory efficiency, Lake bioassessment, Macroinvertebrate, Multi-assemblage, Omnidia, SIMPE
- …
