Browsing by Author "Getahun, Abebe(PhD)"
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Item The Effect of Birbira, Milletia Ferruginea (Hochst.) Baker on Some Barbus Spp. (Cyprinidae, Teleostei) in Gumara River (Lake Tana), Ethiopia(Addis Ababa University, 2004-02) Ameha, Abebe; Getahun, Abebe(PhD)To assess the possible effect(s) of birbira, Milletia ferruginea (Leguminosae) on the barbs, Barbus spp. (Cyprinidae) from Gumara River (Ethiopia), aquarium and field study was conducted during August to September, 2002. The effects of birbira at concentrations of 0.02, 0.04, 0.1, 0.2, 0.3 and 0.4 g/l were studied to conduct experiments on different species, sizes and sexes of fish. The amount of crude powders of birbira seeds actually applied by the fishermen at Dukalit stream (a tributary of Gumara River) was estimated to be about 0.4 g per liter of water. This amount was found to be excessive as only 0.02 g/l (a 5% dilution) was enough to bring about total fish kills in about an hour. It was observed that the amount of oxygen in the birbira solution remained almost intact after all of the fish died, supporting the idea that rotenone does not deplete oxygen dissolved in the water but affects mechanism of oxygen uptake by fish. The findings of the study revealed that when using birbira concentrations of 0.02 to 0.4 g/l, all of the fish died in about 30 to 60 minutes. Comparison of different species showed that B. brevicephalus and juvenile ‘large’ barbs (weighing < 50 g) had relatively better tolerance than had another close relative, Varicorhinus beso of similar weight. Female B. brevicephalus (usually ≥ 100 g) with running (ripe) gonads of tolerated the poison better than their male (usually < 100 g) counterparts. Fertilized eggs, presumed to have been spawned by B. brevicephalus, were collected from Dukalit stream and poisoned with 0.4 g/l birbira for 15 minutes, and then incubated in clean water. None of these eggs hatched while all of the controls (unpoisoned eggs) did after 3 days of collection from the river. The findings of this study are believed to lay a basis for further research and consequently to solve problems related to poisoning fish with birbira and/or other herbs on Gumara River and other waters. Key words/phrases: birbira (Milletia ferruginea); Gumara River (Lake Tana); ‘large’ Barbus spp.; survival time.Item Effect of Feed Quality on Growth Performance and Water Quality in Cage Culture System for Production of Nile Tilapia [Oreochromis Niloticus, (L., 1758)] in Lake Babogaya, Ethiopia.(Addis Ababa University, 2008-07) Fetene, Belste; Getahun, Abebe(PhD); Mengistou, Seyoum (PhD)This research was conducted in Lake Babogaya, Ethiopia, to investigate the effect of feed quality on growth performance and water quality in cage culture system for production of Nile tilapia (Oreochromis niloticus). All the treatments had the same stocking density of 100 fish per m3 cage. Seven different types of test diets (M=T1, D=T2, O=T3, MD=T4, MO=T5, DO=T6, and MDO=T7) were formulated from three locally available diets (M=Mill sweeping, D=Chicken dung, and O=Oil seed cake). The test diets were formulated in a proportion of 100, 50, and 33.3%, respectively. One control group (C) without supplementary diet was used. All treatments including the control group were in duplicate. Mixed sex juveniles with an average weight of 33.62±0.21 g were stocked in all treatments. The fish were fed the test diets at a rate of 3% of their body weight twice per day using feeding trays for 170 days in powder form. The results showed that the growth of Nile tilapia was affected by the quality of the test diets. The final mean weight of O. niloticus ranged from 166.90±1.61 to 242.87±1.97 g and the mean weight gain ranged from 0.79±0.06 to 1.23±0.03 g day-1. The mean feed intake per fish ranged from 2.57 to 3.52 g day-1 while the feed conversion ratio (FCR) ranged from 2.76 to 3.33. Greater FCR for caged tilapia was obtained from T4 and T7 diets with insignificant difference (P > 0.05), while the poorest FCR was obtained from the test diet containing 100% oil seed cake (T3, P < 0.05). There was significant effect of feed quality and culturing periods on condition factor (P <0.05). Water quality parameters were similar (P > 0.05) among the test diets and sampling sites. In conclusion, T4 and T7 treatments were the best diets preferred by Nile tilapia in terms of all the growth parameters in the study and produced the highest growth performance. So chicken dung and mill sweeping should not be used separately to get the maximum fish growth as revealed in T1 (100%), T2 (100%), T4 (50%), and T7 (33.3%). Moreover, oil seed cake can only partially be used as a source of protein in locally formulated diet, at a limited amount of not more than 33.3% as demonItem Effect of Feed Quality on Growth Performance and Water Quality in Cage Culture System for Production of Nile Tilapia [Oreochromis Niloticus, (Linnaeus, 1758)] in Lake Hora-Arsedi, Ethiopia(Addis Ababa University, 2011-05) Alemayehu, Asfaw; Getahun, Abebe(PhD)Six months (Jun 7 to November 22/ 2010) feeding trial was conducted to investigate the effects of feed quality on growth performance and water quality in cage culture system of mixed-sex Nile tilapia (Oreochromis niloticus) in Lake Hora-Arsedi using fifteen suspended 1 m3 net cages. The initial length and weight of the fish ranged from 119.32 ± 1.44 to 125.00 ± 1.50 mm and 42.80 ± 2.53 to 43.51 ± 2.36 gm, (mean ± SD), respectively. Fish diets were prepared from three kinds of locally available plant protein source feeds, i.e. oil seed cake (O), mill sweeping (M), and rice bran (R). In all the combination 20% of blood and bone meal (B) was added to increase the crude protein level and supplement growth limiting mineral, phosphorus. Therefore, four combination of feeds were prepared as diet-1 (ROM+B), 22.87% crude protein (CP); diet-2 (RM + B), 22.22% CP; diet-3 (MO+B), 22.00% CP, and diet-4 (RO+B), 24.28% CP). About 26.67% each of plant protein source ingredient was in diet-1, whereas 40% of it in the other combinations. There was a triplicate of control cages in which fishes were provided with only the natural feeds. Each treatment was assigned to triplicates of 100 fish in a completely randomized design along the U-shaped jetty (walkway). The fish were fed sinking extruded feeds, 3% of their body weight, twice a day manually using feeding tray. The results showed significant differences among the test diets. Diet-1 gave the best mean weight gain (MWGs) of 197.38 ± 5.57 followed by diet-3 with MWGs of 182.16 ± 4.12, diet-2 with MWGs of 169.27 ± 6.31. Diet-4 and the control gave MWGs of 146.27 ± 6.82 and 80.62 ± 3.34 gm, respectively. MWGs in treatment fed with diet-1 were significantly higher (P < 0.05) than MWGs of other treatments. Mean DGR ranged from 0.28 for the control treatment to 0.92 for the fish fed with diet-1. Specific growth rate was also highest in the treatment fed diet-1 (0.9%/ fish) and lowest in the control (0.38%/ fish). Food conversion ratio and efficiency were best with diet-1, followed by diet-3 and least with diet-4. Visceral to body weight ratio for the treatment fed with diet-1 was significantly better (P < 0.05) than the values for other treatments. Percentage survival ranged from 80% in the control to 94% in cages fed with diet-1. The study showed that diet-1 can be effectively used in the diet of O. niloticus and also in terms of cost it sees more efficient than other followed by diet-3. This study also showed that the feeds did not bring any effect on water quality at least in experimental level. Key words: Economic analysis; feed conversion;mill sweeping, rice bran; oil seed cakeItem The Effect of Stocking Density and Supplementary Feeding on Growth Performance and Yield of Nile Tilapia [Oreochromis Niloticus (L, 1758)] in Cage Culture in Wonji Reservoir Ethiopia(Addis Ababa University, 2010-06) Dill, Abdilahi; Getahun, Abebe(PhD); Rana, Krishen (Professor)This research was conducted to investigate the effect of stocking density and supplementary feeding on growth performance and yield of Oreochromis niloticus in cage culture in Wonji Reservoir. The treatments had stocking densities of 25 (25F), 50 (50F), 75 (75F) with supplementary feed and 25 (25N), 50 (50N), 75 (75N) fish per m3cage without supplementary feed. The treatments with supplementary feed were in duplicates and the controls were single. Juveniles with average weight of 43.70 ± 0.19, 43.12 ± 0.5, 43.38 ± 1.14, 43.97 ± 0.36, 43.51 ± 0.33 and 43.98 ± 1.18 gm were stocked in 25F, 50F, 75F, 25N, 50N and 75N treatments, respectively. The fish were fed 3% of their body weight twice per day using feeding trays for 100 days. The results indicated that growth performance of O. niloticus was density dependent. The final mean weight of O. niloticus in 25F was 175.83±0.68 gm and the mean daily weight gain was 1.36 gm, whereas in treatments (50F, 75F) and controls (25N, 50N and 75N), final mean weight was 154.92±0.82, 146.70±0.15, 86.67±0.51, 73.64±0.26, 72.62±0.46 gm and mean daily weight gains were 1.06, 0.77, 0.55, 0.28 and 0.27 gm, respectively. Moreover, feed conversion and condition of fish were affected by stocking density and supplementary feeding. The apparent feed conversion ratio (1.45 – 4.45) was significantly affected by stocking density (P<0.05). Fulton condition factor was inversely affected by stocking density while it was directly affected by supplementary feeding. However, survival rate was not affected by stocking density and supplementary feeding (P > 0.05). In this experiment, it can be concluded that the most effective stocking densities for O. niloticus cultured were at 25 fish / m3 cage for larger size fish demand in short period and 75 fish/m3 for higher gross production with supplementary feed. Physical, chemical and biological parameters were the same among cages or between cages and the open water in the present experiment. Thus, all O. niloticus had similar culture environment and equal access to natural feeds. Key words / phrases: Cage culture, Growth performance, Wonji Reservoir, Nile tilapia, Stocking density, Supplementary feeding.Item Effects of Feed Quantity on Growth Performance and Water Quality in Cage Culture System for Production of Nile Tilapia (Oreochromis Niloticus, L., 1758) in Lake Babogaya, Ethiopia(Addis Ababa University, 2008-07) Hailu, Solomon; Getahun, Abebe(PhD)This study was conducted in Lake Babogaya, one of Bishoftu’s crater lakes in Bishoftu town, to determine the appropriate feeding level for tilapia, Oreochromis niloticus and the impacts of supplementary feed on water quality. A 16.9% crude protein diet, local made feed (Mill sweeping, oilseed cake and chicken dug cake) was fed to duplicate groups of O. niloticus fingerlings (29.70 ± 0.45 – 30.43 ± 0.70 gm) and (120.00 ± 0.56 -122.97 ± 0.54 mm) in cages (1 m x 1 m x 1 m). Fingerlings obtained from Lake Babogaya and stocked at a density of 100 fish/cage. They were feed at 1, 2, 3, 4, and 5% of body weight daily. Water quality parameters, pH, temperature and dissolved oxygen (DO) were measured every month during the culture periods. The results of the experiment revealed that the final weight (224.63 ± 1.23, 223.07 ± 1.23, and 223.40 ± 1.23) and specific growth rate (1.22 ± 0.08, 1.20 ± 0.07, and 1.21 ± 0.06) of the fishes fed at 3, 4 and 5% body weights were similar (p>0.05) but differed significantly (p <0.05) from the final weight (118.30 ± 0.43 and 152.87 ± 0.40) and SGR (0.81 ± 0.08 and 0.99 ± 0.07)of the group of fishes fed at 1 and 2% body weight respectively. Moreover, there were significant differences in FCR of fishes fed at the various body weights (1.76 – 6.33). Survival rate was not affected by feeding level. In addition, pH, DO and temperature of the culture water were not affected by the treatments. The study established the optimum feeding rate for O. niloticus at 3% body weight daily reared in cages. Keywords: Cage, Ethiopia, Feeding Levels, Lake Babogaya, Oreochromis niloticusItem Fish Diversity, Abundance, Socioeconomic Importance and the Status of the Fisheries of Lake Hayq, South Wollo, Ethiopia(Addis Ababa University, 2016-06) Seid, Zuriash; Getahun, Abebe(PhD)This study was conducted on one of the northern high land fresh water lake; i.e., Lake Hayq, and its surrounding fishing community. The current fish diversity in Lake Hayq comprises of 4 species namely, Nile tilapia (Oreochromis niloticus), Catfish (Clarias gariepinus), Common carp (Cyprinus carpio) and Garra (Garra dembecha). However; Garra sp. has no economical value in the research area and hence it is not targeted & presented by fishermen. The fish species that is more abundant in the lake as a whole, around the lake shore and during dry (Begga) season is Nile tilapia, followed by common carp. Whereas, catfish is more abundant in the rainy season (Kiremt) in Lake Hayq. The species of tilapia and catfish are currently being depleted and not adequately captured. Instead, it is been identified that Carp (C, carpio), which has been introduced in to the lake in the recent years, reproduce very well and become dominated the lake. Sustainable fish resource in the lake provides animal protein and means of livelihood to surrounding community. However, it is found that the fish resource in the lake is facing biological and economical challenges. The current socio-economic importance of fish resources in the lake are stressed by demographic and economical pressures. Majority of the fishermen who were engaged in this fishing activities are young ranging from 21 to 30 years old. Individual fishermen daily fish catch exceed 100-200 immature tilapia per individual. Which estimated around 3513.6 quintal in a year. This indicated that in the current situation large number of tilapia (mostly preferred by surrounding community) harvested from Lake Hayq when we compared from past trends, but, low in quality (tilapia sp. become stunted). Due to this reason, individual fishermen monthly income did not exceed 1000 Et. Birr. Majority of them have no other income source for their livelihood and they are totally dependent on the lake’s resources. Members of Logo Hayq-Ardibo fishermen association, on the other hand, found relatively in a better position as a result of their catching effort from Lake Ardibo in addition to Lake Hayq. The problem is aggravated due to little employment diversification opportunity and lack of government support or poor accountability. The major anthropogenic activities that aggravate fish resource destruction are overfishing practices of individual fishermen using non recommended gillnet with mesh size less than 8 cm and continuous fishing even during reproductive seasons of some fishes (eg. Nile tilapia). Moreover, environmental pollution, destruction of fish reproductive sites & water level reduction, further degraded the habitats of the fishes. Generally the absence of effective lake management system accelerated the decline of the fish resources in Lake Hayq. To overcome these adverse impacts on the fish resource, there should be continuous professional follow up, diversification of employment for youth, organization of individual fishers into fishermen association. Moreover, introduction of other systems of producing tilapia species (like aquaculture) to restock the lake is recommended. Furthermore, there is a need for further study about the cause of stunting tilapia in this lake during recent years. Key words/phrases: Lake Hayq, diversity, abundance, socio-economic importance, lake management.Item Fish Diversity, Community Structure, Feeding Ecology, and Fisheries of Lower Omo River and the Ethiopian Part of Lake Turkana, East Africa(Addis Ababa University, 2016-06) Wakjira, Mulugeta; Getahun, Abebe(PhD)Ethiopia has a freshwater system in nine major drainage basins which fall into four ichthyofaunal provinces and one subprovince. Omo-Turkana Basin, spanning considerable geographic area in southwestern Ethiopia and northern Kenya, essentially consists of Omo River (also known as Omo-Gibe) and Lake Turkana. The entire of Omo River and about 1.3% of the lake (ca. 98 km2) lie within Ethiopia. The Ethiopian part of the basin generally lacks comprehensive study and proper scientific documentation on its ichthyofaunal diversity, ecology and fisheries. This study was thus undertaken to address these gaps. Data were obtained using various methods over a period of two years, and analyzed using various computations, univariate tests and multivariate methods. Thirty-one fish species were identified from lower Omo River and the Ethiopian part of Lake Turkana, with some new records, from the present collections. Omo River system was found to be more species rich than Lake Turkana but poorer in abundance. The basin’s extent of ichthyofaunal diversity within the limit of Ethiopia was specifically addressed, for which an artificial identification key was prepared. Annotated checklist for the native species was provided for the entire basin. Composition of the most important species (total index of relative importance, IRI > 94%) was essentially similar for the river and the lake, but differed in the relative importance of each species. Cluster analysis and principal component analysis (PCA) produced distinct habitat-associated species patterns across the riverine and lacustrine environments. The Ethiopian part of Lake Turkana community consisted of 18 fish species, of which two-thirds were species of highest relative importance. The lower Omo River community consisted of 13 species of largely lower IRI. Ionic concentration measured as total dissolved solids (TDS) was found to be the key environmental factor determining fish community structure in lower Omo-Turkana sub-basin. Feeding habits of eight selected fish species from the Ethiopian part of Lake Turkana have been identified and described. Although 11 major prey groups were identified for all species, only 7 prey categories viz. aquatic insects, phytoplankton, macrophytes, fish, zooplankton, detritus and prawn were the most important contributors to the fishes’ dietary variations. Fish, aquatic insects, phytoplankton and zooplankton constituted the most diversified prey categories. The eight species ranged in the generalist-specialist feeding strategy spectrum with Synodontis schall (Bloch & Schneider, 1801) being the most generalist feeder, while Oreochromis niloticus (Linnaeus, 1758) was the most specialist feeder. Each fish species consisted of subpopulations with various dietary niche width contributions to the species’ overall feeding strategy. Ontogenetic and seasonal dietary variations were observed for all the fish species examined except for S. uranoscopus whose diet virtually remained constant across fish size and seasons. The eight examined fish species formed two trophic guilds, with the mainly piscivorous group consisting of Schilbe uranoscopus Rüppell, 1832, Bagrus bajad (Forsskål, 1775) and Lates niloticus (Linnaeus, 1758), and the mainly planktivorous group consisting of ii S. schall, Distichodus nefasch (Bonnaterre, 1788), Alestes baremoze (Joannis, 1835), Citharinus citharus (Geoffroy St. Hilaire, 1809) and O. niloticus. The number of guilds and dietary items that defined guild structures did not vary on seasonal and non-seasonal situations; however, a change in guild organization was observed. The computed Horn’s dietary niche overlap indices corroborated categorization of the examined fish species according to their prime dietary resource utilization. The river and the lake supported small-scale gill net fisheries that provided livelihood, income and employment to three major fisher-categories. Fisheries value chain was developed and major issues arising out of the chain components were addressed, fishers’ perceptions about the resource condition and management status were identified and discussed. In order to sustain fisheries socioeconomic contributions to livelihoods of the local people, the government in particular the regional state should take a prime responsibility to address the major socioeconomic issues arising out of the fisheries value chain analysis and issues related to resource management. Particularly, conflict of the Ethiopian fishers with the rival Turkana tribe fishers of Kenya should be properly addressed as it could jeopardize any attempt of resource management effort. Keywords: Annotated checklist, community structure, diversity, Ethiopia, feeding habits, fish, Lake Turkana, Omo River, small-scale fisheries, socioeconomics, total dissolved solids, trophic guild.Item Nutritional evaluation of some Ethiopian oilseed cakes in the diets of juvenile Nile tilapia, Oreochromis niloticus L.(Addis Ababa University, 2015-05) Geremew, Akewake; Getahun, Abebe(PhD)This study evaluated the suitability of Niger seed cake (NSC) and linseed cake (LSC) inclusion as potential plant protein sources in Nile tilapia, Oreochromis niloticus, diets. A series of four experiments were conducted in a recirculation system using juvenile O. niloticus. The fish were fed diets containing the oilseed cakes at dietary inclusion levels ranging from 20% to 50%. Diets were formulated to be isonitrogenous (32g 100 g-1), isolipidic (10g 100 g-1) and isoenergetic (18 kJ g-1) and fed to juvenile Nile tilapia at 4-10% of their body weight per day for a period of 8 weeks. Niger seed cake (NSC) and linseed cake (LSC) were used individually or as mixtures to test for their effect on Nile tilapia growth and feed utilization. Also of interest was to compare digestibility and feeding values of NSC and LSC with that of soybean cake (SBC), the best plant protein source. Proximate analysis showed that Niger seed cake (NSC) and linseed cake (LSC) had 324.2 and 310.0 g kg-1 crude protein, 201.1 and 136.3 g kg-1 crude fibre and 18.1 and 18.6 kJ g-1 gross energy, respectively. Nutrient digestibility of these oilseed cakes suggested that Nile tilapia may be able to utilize NSC better as dietary protein source due to a reasonably high protein digestibility coefficient (72.6%) than linseed cake (62.4%). Of the three oilseed cakes (NSC, LSC and SBC) tested soybean cake (SBC) produced significantly (P< 0.05) the highest nutrient digestibility coefficients. When Niger seed cake (NSC) and linseed cake (LSC) were used individually as protein sources in Nile tilapia diets, depressed growth and feed efficiency were observed at dietary inclusion levels above 20%. This may be attributed to high levels of antinutritional factors (ANFs), high crude fibre content and poor essential amino acid profile. However, the use of mixtures of these two oilseed cakes (formulation 1 (F1): 50% NSC:50% LSC, Formulation 2 (F2): 33% NSC:67% LSC and Formulation 3 (F3) 67% NSC:33% LSC) was found to be marginally suitable than that of single sources, especially when the proportion of NSC in the mixture is 50% to 67%. The oilseed cake formulations with higher proportion of NSC could be included at 25% dietary inclusion without significantly reducing performance. This may have been as a result of lower levels of ANFs and improvements in the amino acid profile due to mixing. It can be concluded that there is nutritional and economic justification for using NSC and LSC as protein sources in Nile tilapia diets. Based on growth performance, nutrient utilization and economic benefits the diet with F3 formulation at 25% level of inclusion has the best prospects for use in Nile tilapia dietsItem Some aspects of the biology of Garra dembecha [Pisces: Cyprinidae] and Clarias gariepinus [Pisces: Clariidae] in Lake Hayq, Ethiopia(Addis Ababa University, 2009-09) Alemayehu, Esayas; Getahun, Abebe(PhD)Sex-ratio, length-weight relationship, condition factor, food and feeding habits of Garra dembecha (n=580) and Clarias gariepinus (n=121) in Lake Hayq were studied from monthly samples collected by gillnets of various stretched mesh sizes (3, 5, 8, 10 and 12 cm) and long lines between January 2009 and June 2009. Length of G. dembecha ranged form 8 to 13.3 cm for females and from 8 to 14 cm for males. Length of C. gariepinus ranged from 25 to 77 cm for females and from 20.5 to 50 cm for males. Male to female ratio was in favor of males in the total sample of G. dembecha (1.33:1). Sex-ratio was significantly different from 1:1 in three of the six sampling months and also in the total sample. Female preponderance over males in the total sample of C. gariepinus (1.02:1) was observed. Sex-ratio was not significantly different from 1:1 in the total sample of C. gariepinus. The relationship between total length (range: 8-14 cm) and total weight (range: 6-45 gm) of G. dembecha was found to be curvilinear and statistically significant (p<0.05). The slope b was 3.14 for males and 3.11 for females, which was in both cases not significantly different from the expected value of 3 (t-test, p>0.05).Thus, growth of the fish was isometric. The corresponding equations were represented by: Males: TW = 0.0038x TL 3.144 and Females: TW =0.012x TL 3.109 . The relationship between total length (range: 20.5-77 cm) and total weight (range: 75-3500 gm) of C. gariepinus was found to be curvilinear and statistically significant (p<0.05) and suggesting isometric growth. The slope b was 3.04 for males and 3.27 for females, which was not significantly different from the expected value of 3 (t-test, p>0.05). The corresponding equations were represented by: Males: TW= 0.005x TL3.038 and Females: TW=0.002x TL3.274 . Monthly FCF of G. dembecha in this study ranged from 0.8 to 1.73 for females, and from 0.82 to 1.84 for males. Mean FCF+ SE was found to be 1.25+ 0.02 and 1.33 + 0.01 for females and males, respectively, with an overall value of 1.30 + 0.01. Generally, males had larger FCF values than females. Monthly FCF of C. gariepinus in this study ranged from 0.50 to 1.15 for females, and from 0.48 to 1.10 for males. Mean FCF+ SE was 0.69 + 0.02 and 0.67+ 0.02 for females and males, respectively. The overall Mean + SE FCF was 0.68+ 0.02. Generally females had larger FCF than males. Based on a total of 476 gut samples of G. dembecha, the fish was found to ingest a wide spectrum of food items, ranging from various types of phytoplankton to zooplankton, and to sand particles and detritus. The predominant food items, in terms of frequency of occurrence, were Melosira, Tetraedron, Amphora, Nitzchia, Cymbella, Microcystis, Fragillaria, Cosmarium, Suririella, Navicula and Daphnia. Numerically, Nitzchia, Tetraedron, Cosmarium and Melosira dominated the food of G. dembecha. The contribution of Daphnia was low. Moreover, the fish had ingested detritus, and sand grains. Stomach content samples (n= 121) of C. gariepinus showed that C. gariepinus feeds on a variety of items of both plant and animal origin ranging from phytoplankton to zooplankton, to insects and fish. Macrophyte shoots and detritus were also among the most frequently found items. The predominant food items in terms of frequency of occurrence were crustaceans, followed by insects and fish. Numerically as well, crustaceans (98%) were the most important items followed by insects (0.028%) and fish (0.0045%). Mesocyclops were the most numerous genera in the diet of C. gariepinus (37%) followed by Thermocyclops (31%), Daphnia (14%) and Cerodaphnia (14%). Monthly variation, both in frequency of occurrence and numerical abundance, was also noted in the gut contents of G. dembecha over the period of investigation. Diatoms contributed the highest number in 4 of the 6 sampling months (January to April); while Cyanophyta (40%) in May and Chlorophyta (60%) in June contributed the highest number. Monthly variation among the major food groups was observed in C. gariepinus in the present study. Insects were encountered in greater number of stomachs in the months of January (57%), March (55.56%), April (75) and May (83.33) while Crustacea appeared more frequently in February (77.78%), March (55.56%) and June (77.78%). Fishes were absent entirely in April and June. All the size groups of C. gariepinus ingested all the major food items. This suggests that C. gariepinus, at all sizes, is an indiscriminate feeder in Lake Hayq. However, the relative contribution of items of C. gariepinus varied with fish size. The contribution of insects decreased with increasing fish size, whereas the contribution of zooplankton increased with increasing size. Key words: Condition factor, food and feeding habits, Lake Hayq, length-weight relationship, G. dembecha, C. gariepinusItem Taxonomic Revision, Relative Abundance, and aspects of the Biology of Some Species of the Genus Garra, Hamilton 1922 (Pisces: Cyprinidae) in Lake Tana, Ethiopia(Addis Ababa University, 2007-08) Geremew, Akewake; Getahun, Abebe(PhD); Dejen, Eshete (PhD)Taxonomic revision, relative abundance, reproductive biology, length-weight relation, condition factor and aspects of feeding of Lake Tana Garra species were studied from 2187 fish collected during January to December, 2006. Morphological, psychometric and mesmeric characters were used to revise the taxonomy of the three already described species (G. tana, G. dembecha and G. regressus) and one different form of Garra (small mouth, sm). Cluster and principal component analyses using 23 external and 14 skull bone morphometric measurements revealed that G. tana and G. regressus are separate dissimilar species from others. G. dembecha and G. sm showed some similarities, though the few meristic and morphological features were important to differentiate them. The % IRI (Index of Relative Importance) indicated that G. tana is abundant in the pelagic sites whereas G. sm is abundant in the littoral, and sub littoral sites having the rest of Garra species less abundant. Gonad-somatic index (GSI) and % frequency of ripe females were used to determine main breeding season. The main breeding time of G. regresses (April-October), G. tana (March-July) and G. December (May-July) was coincident with the rainy season of the area. G. sm was found to breed intensively during the dry season (November-March). G. tana is capable of breeding throughout the year, whereas G. December breeds only for three months. Extended breeding times were observed in G. sm and G. regresses. Significant differences were observed between the species for both sexes in the mean size at maturity, except for G. sm and G. December. Absolute fecundity was found to be related rectilinear with standard length and linearly with body and gonad weight for G.sm Regress and G. tana. The range of absolute fecundity was (538.9-2968), (606-3397), (1215-1229) and (580.8-1800) for G. tana, G. sm, G. dembecha and G. regressus, respectively. The average relative fecundity was 63.3, 77.1, 102.7, and 55.5 for G. dembecha, G. sm, G. tana and G. regressus, respectively. Both relative and absolute fecundity were statistically different (P< 0.001) between the species. Egg size frequency distribution revealed that G. regresses was found to be multiple spawner, while G. December; G. tana and G. sm were single spanners. Except for G. December and G. regresses (Chi-square, P< 0.05), the sex ratio in the total catch was not different from 1:1 for the other two species. The relationship between standard length and total weight was curvilinear for all the species, and isometric growth was assumed for all. A significant seasonal fluctuation (P< 0.0001) was observed in the condition of all Garra species. The better condition of these fishes during late dry and pre-rainy seasons was attributed to the increase in temperature and availability of food. Microscopic examination of gut contents of G. sm, G. tana and G. December indicated that green, blue-green, diatoms and zooplanktons that are detrimental in their origin were dominant. Key words and phrases: Condition factor, Food items, Garra, Lake Tana, Length-weight relation,Relative abundance, Reproductive biology, and Taxonomic revision.