African Journals Online
SINET: Ethiopian Journal of Science

ABSTRACTS (VOL. 23, NO. 1)

THE FOOD AND FEEDING HABIT OF OREOCHROMIS NILOTICUS L. (PISCES: CICHLIDAE) IN LAKE CHAMO, ETHIOPIA

Yirgaw Teferi ¹, Demeke Admassu ² and Seyoum Mengistou ²

¹ Animal and Fisheries Resources Development and Regulatory Department MoA, PO Box 62347, Addis Ababa, Ethiopia

² Department of Biology, Faculty of Science, Addis Ababa University PO Box 1176, Addis Ababa, Ethiopia

ABSTRACT: The food of Oreochromis niloticus in Lake Chamo, Ethiopia was studied from the stomach contents of 449 adult (290B570 mm total length, tl) and 145 juvenile (61B115 mm tl) fish. O. niloticus was found to be essentially phytoplanktivores in Lake Chamo, and the composition of the phytoplankton diet varied seasonally. The diet of both adult and juvenile fish consisted of 10 genera of blue greens whereas green algae and diatoms each contributed 8 genera. Blue greens as a group contributed the bulk of the diet of adult fish. The most frequently encountered genera from the blue greens were Anabaena (96B100), Lyngbya (85B100), Microcystis (81B100) and Oscillatoria (41B100). Cosmarium (79B100) from the green algae and Navicula (82B100) from the diatoms were also frequently observed. In terms of percentage composition by number, the blue greens contributed over 60% of the total food ingested. Of these, more than 50% was due to Anabaena, Lyngbya and Microcystis. Zooplankters occurred on rare occasions in the stomach contents of both adult and juvenile fish. The feeding pattern of adult O. niloticus was observed to have a diel rhythm. O. niloticus in Lake Chamo is a continuous feeder during the day and peaked at 16 hr. Daily ingestion of phytoplankton was estimated to be about 3.7% of its wet body weight at an average water temperature of 26E C.

Key words/phrases: Ethiopia, Food, Lake Chamo, Oreochromis niloticus

SEASONAL VARIATIONS DETERMINE DIET QUALITY FOR OREOCHROMIS NILOTICUS L. (PISCES: CICHLIDAE) IN LAKE TANA, ETHIOPIA

Getachew Teferra ¹, S.H. Bowen, ² Eyualem Abebe ³ and Zenebe Tadesse ³

¹ Department of Biological Sciences, University of Botswana Private bag 00704, Gaborone, Botswana

² Department of Biological Sciences, Michigan Technological University Houghton, MI, 49931, USA

³ Department of Biology, Bahir Dar Teachers' College PO Box 79, Bahir Dar, Ethiopia

ABSTRACT: The diet composition and its use by Oreochromis niloticus in Lake Tana, Ethiopia, were studied from monthly samples taken over 13 months. The composition of the diet varied seasonally, with dramatic increases in quality following seasonal climatic events (rainfall, vertical mixing) that bring plant nutrients to the photic zone. Thus, organic matter in the diet increased four-fold, from 150 to 600 mg g^-1 of diet. Protein content increased from 71 to 256 mg g^-1 ash free dry weight (afdw). Assimilation efficiency increased from 8.3% to 43.2% for afdw, and from near 0 to 45.8% for protein. The fraction of organic matter that is refractory declined from 800 to 27 mg g^-1 afdw. Condition factor followed the same pattern, but lagged 1 to 2 months behind changes in diet quality. It was concluded that seasonal pattern of rainfall and temperature affect pelagic food resources, hence heterogeneity in diet quality is temporal to a great extent for O. niloticus in Lake Tana.

Key word/phrases: Assimilation efficiency, condition factor, food quality, Lake Tana, protein-energy ratio

PRELIMINARY SURVEY OF PARASITES AND BACTERIAL PATHOGENS OF FISH AT LAKE ZIWAY

Eshetu Yimer

National Animal Health Research Centre
PO Box 181689, Addis Ababa, Ethiopia

ABSTRACT: Parasites and bacterial pathogens of fish at Lake Ziway, during 1996B97 were studied. A total of 613 fish were sampled. These included 495 Nile tilapia (Oreochromis niloticus), 75 Catfish (Clarias gariepinus), 24 Barbus species, 11 Tilapia zillii and 8 carp species. The fish were thoroughly examined both externally and internally for the presence of parasites and lesions and samples were taken for bacteriological investigations. Among the bacteria, Edwardsiella tarda, (new geographic record) isolated from the liver of one O. niloticus and kidney of another carp species is known to be pathogenic to fish. On the other hand Shigella species, Escherichia coli, Citrobacter, Klebsiella oxytoca, and Yersinia enterocolitica were the major bacteria identified from the apparently healthy fish. The major parasites identified included Contracaecum species from 77 (15.56 %) of O. niloticus, 3 (27.27%) T. zillii, 4 (5.33%) C. gariepinus and 2 (8.33%) Barbus species. Clinostomum species were recovered from the branchial cavity of 45 (9.09%) Oreochromis niloticus, 2 (18.18%) Tilapia zillii and 3 (4.00%) C. gariepinus. Only 1 Euclinostomum species (new geographic record) was recovered from the branchial cavity of O. niloticus. Moreover 13 (17.33%) C. gariepinus were carrying Amplicaecum species in their mesentery and one C. gariepinus was positive to Bothriocephalus species. The significance of these parasites and bacterial pathogens as causes of diseases to fish is discussed.

Key words/phrases: Bacteria, Edwardsiella tarda, fish diseases, Lake Ziway, parasites

CHARACTERISTICS AND CLASSIFICATION OF SOILS OF GORA DAGET FOREST, SOUTH WELO HIGHLANDS, ETHIOPIA

Belay Tegene

Department of Geography, Addis Ababa University
PO Box 150085, Addis Ababa, Ethiopia

ABSTRACT: The soils of the slopes of the South Welo highlands have been either intensively cultivated or overgrazed and eroded. As a result there are few sites where undisturbed soils exist for use as a reference against which the impacts of land use can be evaluated. The Gora Daget forest on a very steep slope located close to Dessie town provides one of these rare opportunities for the type of investigation. Three pairs of representative soil profiles that formed under this indigenous mixed juniperous forest were investigated to establish the soil characteristics and identify the grouping within the fao/unesco classification system. The depths of the soils ranged from less than 30 cm to slightly more than a meter. The solum in all soil types showed very little horizon differentiation and comprised of only Ah horizon, where it is shallower, and Ah and ac horizons where it is deeper. The Ah colour is invariably dark brown (10yr2/2) while the ac is black (10yr2/1). The crumb structure and the loam texture typifying the surface soils changes very little with depth. The main minerals constituting the clay fraction were mica, morderite and sepiolite while those comprising the skeletal fraction were pyroxenes, anorthoclase, plagioclase, morderite, quartz, and magnetite. The organic carbon and total nitrogen are generally high but available phosphorus is low. The pH is within a range suitable to most plants while both the cec and base saturation values registered for the soils were high. The A-horizons were mollic and the soil units were identified as Mollic Leptosols and Mollic Phaeozems. All of the soils showed transitional characteristics with Andosols necessitating their third-level categorization as Andi-mollic Leptosols and Andi-mollic Phaeozems.

Key words/phrases: Ethiopia, Gora Daget forest, soils, Welo highlands

RESPONSE OF BREAD WHEAT TO INCREASING MUSTARD MEAL NITROGEN APPLICATION ON PELLIC VERTISOL AND EUTRIC NITOSOL

Balesh Tulema ¹ and M. P. Salema ²

¹ Holetta Research Centre, earo
PO Box 2003, Addis Ababa, Ethiopia

² Joint fao/iaea Division of Nuclear Techniques in Agriculture
Wagramerstrasse 5, A 1400, PO Box 100 Vienna, Austria

ABSTRACT: Mustard seed meal was evaluated on the field as source of nitrogen for bread wheat on Pellic Vertisol and Eutric Nitosol in a split plot design with three replications. Highly significant yield increases were obtained due to mustard meal nitrogen rates during all the experimental periods on the Vertisol. The increase in the grain yields of wheat was linearly related to the mustard meal nitrogen rates (r=0.98 and 0.96 for fresh and decayed meal, respectively) and varied from two to ten fold of the control. On the Nitosol, significant effect was obtained only in one crop season. Greenhouse experiment on the nitrogen uptake from the mustard meal using ¹⁵N showed significant difference on both soil types. On the Vertisol the per cent nitrogen derived from the meal and per cent nitrogen use efficiency varied from 18 to 40 and from 18 to 62%, respectively. On the Nitosol, these values varied from 25 to 71 and from 43 to 62%, respectively. Application and incorporation of the mustard seed meal into the soil 20B25 days before planting minimised the toxicity of the meal on seed germination and seedling growth.

Key words/phrases: Eutric Nitosol, mustard seed meal, nitrogen use efficiency, Pellic Vertisol, wheat

TOTAL SHRINKAGE VERSUS PARTIAL SHRINKAGE IN MULTIPLE LINEAR REGRESSION

Eshetu Wencheko

Department of Statistics, Faculty of Science
Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia

ABSTRACT: The paper discusses the merits of partial shrinkage of the ordinary least square estimator of the coefficients of the multiple regression model of full rank. Theoretical comparisons of scalar and matrix-valued risks of the partially shrunken and totally shrunken estimators are given. The strategy of partial shrinkage is applied to two data sets.

Key words/phrases: Partial and total shrinkage, variance inflation factors

COMMON TOXIGENIC FUSARIUM SPECIES IN MAIZE GRAIN IN ETHIOPIA

Tesfaye Wubet ¹ and Dawit Abate ²

¹ Department of Biology, Alemaya University, PO Box 138, Dire Dawa, Ethiopia

² Department of Biology, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia

ABSTRACT: Prevalence of toxigenic species of Fusarium in maize samples collected in Ethiopia was investigated. The three toxigenic species of Fusarium most often associated with Ethiopian maize grain were Fusarium verticillioides [= F. moniliforme] (51.7%), Fusarium subglutinans (24.2%) and Fusarium graminearum (13.9%). Other Fusarium species contributed 10.2% of the total species recovered. A large number of strains of F. verticillioides, F. subglutinans and F. graminearum are known to produce toxic secondary metabolites. The incidence of Fusarium species and the mycotoxins they produce have been positively correlated with numerous toxicoses of man and animals. Thus, the prevalence rate of these toxigenic Fusarium species in Ethiopian maize, destined for human consumption, suggests the possible contamination of maize and its products by Fusarium mycotoxins.

Key words/phrases: Ethiopia, Fusarium, maize, malt, mycotoxins

CHARACTERIZATION OF BACILLUS SPP. FROM SOME SPICES AND ASSESSMENT OF THEIR SPOILAGE POTENTIAL IN

VARIOUS TRADITIONAL ETHIOPIAN SAUCES

Feleke Moges¹ and Mogessie Ashenafi²

¹ Department of Biology, Faculty of Science

² Department of Microbiology and Immunology, Institute of Pathobiology
Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia

ABSTRACT: One hundred twenty five samples from five different Ethiopian sauce spices were examined for the incidence and level of contamination of Bacillus species. The spices consisted of fenugreek (Trigenella foenum-graecum), black cumin (Nigella sativa), Ethiopian caraway (Trachyspermum ammi), ginger (Zingiber officinale) and korarim cardamon (Aframomum corrorima). Spore counts ranged from log 1.63 cfu(g)^-1 in cumin to log 8.32 cfu(g)^-1 in ginger. Of the 781 Bacillus isolates obtained, the most frequently encountered species was Bacillus pumilus (43.7%) followed by B. subtilis (16.6%), B. circulans (11.2%), B. licheniformis (8.2%) and B. cereus (4.9%). The B. pumilus and B. subtilis isolates were active in proteolysis and lipolysis, whereas B. cereus isolates were more proteolytic and amylolytic. All test strains grew well in three different types of traditional Ethiopian sauces, but growth was markedly lower in vegetable-based sauces. Spoilage was manifested only in the form of foul odour, and was noted faster in legume-based sauces (< 24 hours) than in meat-based (24B36 hours) and vegetable-based (48B60 hours) sauces.

Key words/phrases: Bacillus spp., Ethiopia, sauces, spices, spoilage

Short communication
TENSIONAL FISSURES IN SEDIMENTS AS SIGNATURE OF RIFT TECTONICS IN THE MAIN ETHIOPIAN RIFT

Laike Mariam Asfaw

Geophysical Observatory, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia

ABSTRACT: The Main Ethiopian Rift, which forms the northern part of the East African Rift, is a regime of extensional tectonics with geodetically measured mean spreading rate of 3.6 mm(yr)^-1. Earlier studies have shown that the effects of this extension are manifested mainly through earthquakes, faults and volcanism. Recently, with the observations of the occurrence of fissures of tectonic origin on the sediment cover of the rift floor, an additional effect of the extensional process has been identified. The importance of this effect in characterizing rift tectonics could be commensurate with the areal size of the sedimentary cover of the rift floor which is substantial. The object of this study is to assess the significance of these tectonic-induced fissures as signature of the rifting process by comparing them to earthquake and volcanic activities. It is shown that fissures on sediments are significant indicators of rift tectonics with a corresponding role as agents of strain release.

Key words/phrases: Earthquakes, fissures, sediments, signature, strain release, tectonics

Short communication
PREVALENCE OF INTESTINAL HELMINTHIC INFECTIONS AMONG HOUSEHOLD RATS IN ADDIS ABABA

Moges Kassa and Tsehai Assefa

Ethiopian Health and Nutrition Research Institute
PO Box 1242, Addis Ababa, Ethiopia

ABSTRACT: This paper reports the prevalence of intestinal helminthic infections among 101 Rattus rattus collected in Addis Ababa, from November, 1996 to December, 1997. Examination of faecal samples from each rat by the formol-ether concentration technique revealed that 44/101 (43.6%) of the rats were positive for a single intestinal parasite: 31/101 (30.7%) for Hymenolepis diminuta, and 13/101 (12.9%) for Hymenolepis nana. Double infection was recorded in 7/101 (7%). Among the double infection, 3% were infected with H. diminuta and H. nana, and 4% with H. diminuta and Syphacia obveleta. H. diminuta was the most frequent followed by H. nana. S. obveleta was found only in association with H. diminuta. The infection rates for cestodes in the present study were compared with the rates reported for cities in other countries. These findings suggest that household rats could be potential sources of human infections in the areas studied.

Key words/phrases: Hymenolepis diminuta, H. nana, Syphacia obveleta, household rats, Addis Ababa

Short communication
RESISTANCE PATTERNS OF AEROMONAS SALMONICIDA TO COMMON ANTIMICROBIAL AGENTS

Eshetu Yimer

National Animal Health Research Centre
PO Box 181689, Addis Ababa, Ethiopia

ABSTRACT: The antibiotic sensitivity profiles of a collection of Aeromonas salmonicida isolates obtained from a range of geographical locations in Scotland was investigated. The investigation was part of a collaborative study to characterise A. salmonicida on a range of parameters which include cytotoxicity, virulence, autoagglutination and outer membrane protein profiles. Twenty eight isolates, including A. salmonicida fcs strain and A. salmonicida 1102, were subjected to antimicrobial sensitivity testing of 11 antimicrobial agents by a disc diffusion method and an agar dilution method to determine minimum inhibitory concentrations (mic's). The semi-quantitative results of the disc test were confirmed and a more precise value obtained by the second method. Seven different sensitivity patterns were detected. All the 12 isolates which were resistant to oxolinic acid were found to be resistant to the 5 antimicrobial agents oxytetracycline, oxolinic acid, sulphamethoxazole and the potentiated-sulphonamides Romet-30 and co-trimoxazole.

Key words/phrases: Aeromonas salmonicida, antimicrobial, disc diffusion