Browsing by Author "Fetahi, Tadesse (PhD)"
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Item Aquatic Sciences, Fisheries and Aquaculture Stream Assessment of the Ecological Condition of Aba Samuel Reservoir Using Water Quality and Trophic Status Indices(Addis Ababa University, 2019-06-06) Retea, Badatu; Fetahi, Tadesse (PhD); Mengistou, Seyoum (Professor)Aba Samuel Reservoir (ASR) has been degraded by various types of environmental pollution released from domestic, industrial and agricultural activities. This research aimed at evaluating the ecological condition of ASR using water quality and trophic status indices. In situ measurements of physicochemical parameters (DO, Temperature, EC, and pH) were taken from five sampling sites using portable Multimeter. The major inorganic nutrients (NO3-N, NO2-N, NH4, PO4, and TP) were analyzed in the limnology laboratory using APHA methods and microbial analyzed in biomedical laboratory at AAU. Relationships between plankton and environmental variables were analyzed using Principal Component Analysis (CANOCO for Windows 4.5). Water quality indices of ASR calculated using National Sanitation Foundation Water Quality Index (NSFWQI) had overall mean + SE values of turbidity (105.94 + 39.27 NTU), TSS (745.73 + 222.74 mg L-1), pH (7.96 + 0.049), Temp. (21.9015 + 0.29 °C), DO (3.4615 + 0.25 mg L-1), NO3- N (0.25 + 0.015 mg L-1), TP (0.12 + 0.008 mg L-1) and FC (225 CFU 100 mL-1). According to NSFWQI, bad ecological condition of 37.14, WQI was calculated for ASR recorded from all sampling sites. Trophic status index was calculated by Lamparelli (2004) and Cunha et al., (2013) methods proposed for tropical environments. The overall mean phytoplankton biomass as chlorophyll a was (Chl a, 15.08 + 0.94 μg L-1) and Total phosphorus (62.92 + 0.42 μg L-1). Overall ASR WQI is poor and TSI (56.81 _ 61.80) state that sites has TSI values ranging from eutrophic to supereutrophic and that the overall TSI is in the eutrophic category. Lack of industrial and municipal wastewater treatment plants of the Addis Ababa towns and cities in the basin has caused serious pollution to Aba Samuel Reservoir.Item Ecosystem structure, trophic link and functioning of a shallow rift valley lake: the case of Lake Ziway (Ethiopia(Addis Ababa University, 2011-06) Hailu, Mathewos; Fetahi, Tadesse (PhD)A trophic model was constructed for the Lake Ziway ecosystem using Ecopath with Ecosim application software. This model was used to evaluate and analyze the food web structure and other properties of this ecosystem. The mean Chlorophyll a biomass of 70.46 μg L−1was found which is higher than those of earlier reports. Wet weight value of phytoplankton was estimated to be 15.99 tons km-2. A total of 4 cladocerans and 2 copepods were identified. The biomass of zooplankton is dominated by Thermocyclops (127.73 mg WW m-3). A total of fourteen families of macro-zoobenthos were identified which were dominated by chironomids (15924 individuals m-2) that were attached with the macrophyte Typha anguistifola. The above ground biomass of macrophytes vegetation of Lake Ziway was estimated as 3011.68 tons WW km-2. The total mortality value for Carp and Catfish was 0.74 and 1.34 year-1 respectively. The total annual catch from Lake Ziway was estimated at 1127 tons based on the catch and effort data (2008– 2010). The estimated annual catch in tons per gear type was 683.11, 62.97 and 295.98 for beach seine, gill net and long line, respectively. The results of Ecopath with Ecosim modeling showed the presence of six aggregated trophic levels (TLs). The fractional trophic level assigned TLs of Lake Ziway ecosystem between 1.0 and 3.29. The biomass flow was highly restricted to I and II trophic levels which contributed 99.76 %. The mean transfer efficiency was only 4.4%. The fishery catch consumed 2.5% of the primary production in the lake. Low ecotrophic efficiency (EE) of 0.47 was calculated for the phytoplankton indicating that most of the production remains within the system unutilized. A high value of EE was noted for carp (0.99), indicating that it is subjected to high fishing pressure despite its low biomass. In Lake Ziway, EE values were high for all fish groups, indicating that the fish groups were highly constrained by a combination of fishing and predation mortality. Management scenario using Ecosim analysis indicated that increasing catfish mortality by 1.50 times resulted in increment of tilapia to 1.6 times the current biomass in four years period and leveling of its biomass to 1.16 times the current value at the end of the tenth year. Doubling in mortality of catfish resulted in increment of tilapia biomass to 1.12 times the current biomass. Decreasing the effort of beach seine did not benefit the tilapia group as their biomass declined to 0.98 and 0.66 which is related to biomass increment of catfish. The final scenario of increasing the effort long line by 1.50 and 2.00 times benefited tilapia and significantly decreased the catfish community from the ecosystem. The total analysis indicated that lake Ziway ecosystem has an open niche which can be filled with obligate herbivores to increase the energy transfer efficiency of the lake. Key words: Ecopath with Ecosim, Biomass, Transfer efficiency, Trophic modeling, Species introductionItem Effect of Water Quality, Common Carp (Cyprinus Carpio) Invasion, and Fishing Activities on the Population of Nile Tilapia (Oreochromis Niloticus) in Lake Hayq, Ethiopia(Addis Ababa University, 2020-06-05) Tessema, Assefa; Getahun, Abebe (Professor); Mengistou, Seyoum (Professor); Fetahi, Tadesse (PhD); Dejen, Eshete (PhD)Ethiopia is endowed with a number of lakes located across the country in different ecological regions. However, most lakes are found clustered in the Ethiopian Rift valley but there are also few lakes located in the Ethiopian highlands (>1800 m a.s.l.). Lake Hayq is one of the highland lakes located in the north central highlands of the country. The lake fishery provides economic and ecosystem services to the local community. However, since 2010, the fishery production of the lake in general and the population of Nile tilapia, in particular, have been reduced. In addition to this, the growth of Nile tilapia has been stunted. There is limited information on factors that might have contributed to the low population and stunted growth of Nile tilapia in Lake Hayq. Therefore, this study aimed at assessing possible internal and external factors that could have contributed to the decline of Nile tilapia fish growth and the fishery. To realize these objectives, I determined physicochemical water quality, plankton community structure, fish diversity, relative abundance and some biological aspects of common carp (Cyprinus carpio) and Nile tilapia (Oreochromis niloticus) and assessed the effect of fishing activities on O. niloticus between January and December, 2018 using standard methodology. Though significant difference (ANOVA, P< 0.05) was observed in Dissolved Oxygen (DO) and water temperature between dry and wet seasons, variability in most of the physicochemical parameters was low in Lake Hayq. The low variability in physicochemical parameters could be associated with less climatic variability (rainfall and water temperature) and higher depth of the lake. The depth profile data showed that the physicochemical parameters including DO and temperature variation were less between the surface and the deeper portion of the lake. Hence, the lake was not stratified during our sampling period. In this study, the reduction in the concentration of total phosphorus (TP) and Chlorophyll-a (Chl-a) and increment in Secchi disk depth (SD) was observed. Thus, the change in these parameters contributed for the change in the trophic state of the lake from eutrophic to mesotrophic state. A total of 44 phytoplankton taxa grouped under six divisions: Chlorophyta, Bacillariophyta, Cyanophyta, Euglenophyta, Dinophyta, and Cryptophyta were identified in Lake Hayq. Chlorophyta and Bacillariophyta were the major groups in terms of species composition. Peridinium (Dinophyta) was the most numerically abundant species in most of the sampling seasons and sites and formed blooms. Currently, a total of 28 zooplankton taxa were identified from Lake Hayq. The number of both phytoplankton and VI zooplankton taxa was higher in this study which could be associated with a higher number of sampling sites and two of them were from the shore of the lake which might have used as refuging and feeding sites. A total of 1980 fish specimens belonging to three species, Cyprinus carpio (1055), Oreochromis niloticus (892), and Clarias gariepinus (33) were collected. The dominant fish species in abundance were C. carpio (53.28 %), followed by O. niloticus (45.05 %). The length and weight relationships showed nearly isometric growth in both female and male C. carpio. Males (596) were more numerous than females (459) which showed a significant deviation from the 1:1 hypothetical sex ratio in C. carpio. The length at first sexual maturity (L50) of female and male C. carpio were 21.5 and 17.5 cm, respectively. The length and weight relationships in O. niloticus showed negative allometric growth in both female and males. Male O. niloticus were more numerous (553) than female (339) which was deviated from a hypothetical 1:1 sex ratio (Females: Males). The size at first sexual maturity (L50) of females and males O. niloticus were 12.8 and 12.9 cm, respectively. Both C. carpio and O. niloticus have similar peak breeding season between February and April. In Lake Hayq, diet overlap was observed at a smaller size (< 12 cm for O. niloticus and < 16 cm for C. carpio). Fishing activities in Lake Hayq were fully illegal, fishermen have been used monofilaments of mesh s sizes of 4- 6 cm (below the recommended mesh size, > 8 cm). In addition to this, the selective fishing pressure on O. niloticus was higher for Nile tilapia. The change in trophic state from eutrophic to mesotrophic (low food availability), presence of similar breeding season, diet overlap, and fishing pressure (overfishing) especially on O. niloticus might have contributed for stunted growth of O. niloticus in Lake Hayq. Therefore, monitoring the limnological variables, restocking O. niloticus fingerlings, and closing the lake at least for two consecutive years should be done to improve the fishery of Lake Hayq in general and O. niloticus in particular.Item Effects of Water Hyacinth (Eichhornia Crassipes) on Water Quality and Composition and Abundance of Phyto- and Zooplankton in the Littoral Region of Koka Reservoir, Ethiopia(Addis Ababa University, 2019-05-05) Getnet, Habtamu; Kifle, Demeke (PhD); Fetahi, Tadesse (PhD)Invasion of aquatic habitats by non-native species is a global environmental challenge with serious ecological, social and economic consequences demanding urgent action. Water hyacinth, Eichhornia crassipes (Martius) Solms, is one of the world’s most rampant invasive aquatic plants recognized as one of the top 10 worst weeds in the world. Its appearance in Koka Reservoir was reported in 1965 and has become a threat to the aquatic ecosystem. Although several limnological studies have been made on the reservoir, the effects of water hyacinth on water quality and plankton have not been addressed. Samples were collected monthly from three weed-infested and three non-infested sites from March to July 2018 to assess its effect on water quality, plankton composition and abundance in the reservoir. Potential toxicity of water hyacinth extract was also investigated using white albino mice. During this investigation, the differences between weed-infested and non-infested sites in DO, NO3-N, NO2-N, SRP, TP, NH3, TSS, Turbidity, Silica and Secchi disk depth were significant (P<0.05), with lower values in the weed-infested sites except values of TSS, Silica and Turbidity higher in the weed infested sites. The phytoplankton community, which was constituted of 62 species, was dominated by Bacillariophyceae (mainly Aulacoseira granulata) followed by Cyanophyceae (Cylindrospermopsis spp., Microcystis aeruginosa, and Anabaena flos-aquae) and Chlorophyceae in both non-infested and weed-infested sites. The variations in the abundance of phytoplankton and zooplankton between the two sites were significant (p<0.05). The phytoplankton species Monorophidium griffithii and Gyrosigma obtusatum and the zooplankton taxa Lecane monostylahomata, Lecane leontita, Trichocerca djurellasejunctipes, Euchlanis menta, and Platyias quadricornis var. bervispinus were found only in the weed-infested sites. Significant differences in Shannon’s index (H'), species richness (d) and species evenness (j) of zooplankton and species richness (d) of phytoplankton were also observed between the two sites, with higher mean values in the non-infested sites than in the weed-infested sites (p<0.05). Rotifers, followed by Copepods and Cladocerans in the same order, were the most abundant at both sites. The relative density of Rotifers and Cladocerans was higher in the non-infested sites, while that of Copepods was higher next to Rotifesrs in the weed-infested sites. Results of the experimental test on the toxicity of water hyacinth on white albino mice showed unusual changes although the death of the treated mice was not observed suggesting the potential toxic effect of the weed on aquatic biota that would occur with an increase in dose and duration of administration. The existing infestation level of water hyacinth poses a significant effect on water quality, composition and abundance of phytoplankton and zooplankton. The current environmental conditions are favorable for the optimum growth of the weed and further proliferation of the weed and spread to new areas are possible worsening its adverse effect to the ecosystem. Thus, continuous monitoring and development of a sustainable management strategy and regulation of agricultural and urban wastes, have to be addressed.Item Field and Experimental Studies on Phytoplankton-Zooplankton Interaction in Lake Koka, With Particular References to Control of Microcystis Species(Addis Ababa University, 2018-07-05) Tialye, Aynalem; Kifle, Demeke (PhD); Fetahi, Tadesse (PhD)Blooms of Microcystis aeruginosa frequently occur in many eutrophic lakes in Ethiopia,however, there is very little experimental study on the relationship between Microcystis and Zooplankton from Ethiopian waters. The effects of different concentrations of toxic M. aeruginosa on two common freshwater zooplankton Cladoceran (Moina micrura)and Cyclopoid were investigated in laboratory experiments. The main purpose of this study was to examine if there is a difference in the development of tolerance to toxic Microcystis among two species of zooplankton copepoda (Cyclopoid) and a cladocera (Moina micrura )exposed to toxic Microcystis. We tested whether exposure to a toxic strain of cyanobacteria (Microcystis) affects survival, and growth, of a common herbivore, Cyclopoid and cladoceran(Moina micrura). In the experiments, cultures from the lakes will be test at five concentrations of toxic Microcystis aeruginosa: 0%, 20%, 50%, 80% and 100%.After 16 days, we compare the ability of these two populations to withstand the toxic Microcystis by assessing survivorship, and growth rate.Field study showed that Surface water temperatures of all sampling sites were within the range of variation reported for most tropical water bodies (23- 25ºC). Surface water DO(mg L-1), which was varied from 5.48 of the HEPP site to 6.99 of the MetoAleka shore site. Mean levels of nitratevaried between 0.11 HEPP and 0.224 mg L-1 Tannery, while those of ammonia ranged from 0.054 of the MetoAlekashore site to 0.033 Tannery mg L-1. Mean SRP (in mg L-1) 0.083 and 0.09 MetoAleka shore, TP, ranged from 0.254 mg L-1 Tannery of the site to 0.298 mg L-1 of the MetoAleka shore). The phytoplankton communities of all sampling sites were dominated, in terms abundance, by three alga groups, Cyanobacteria (blue-green algae), Bacillariophyceae (diatoms) and Chlorophyceae (green algae). Chlorophyceae was the most species-rich taxonomic group, followed by Cyanophyceae and Bacillariophyceae. The most abundance species were Microcystis sp, and Planktothrix cf.agardhii in Lake Koka. The zooplankton community in Lake Koka was dominated by the copepod which accounted for about 56% of total zooplankton abundance. From experimental result we get more survival rate for cladoceran treatment and low for copepod treatment. It can be suggested that biomanuplation controlling methods can be used to improve water quality in Lake Koka .Item Heavy Metal Levels in the Water and Sediment Samples of Dire and Aba-Samuel Reservoirs,Ethiopia(Addis Ababa University, 2019-05-05) Fenta, Abere; Fetahi, Tadesse (PhD); Kifle, Demeke (PhD)Dire is among the main sources of drinking water supply for Addis Ababa city while Aba-Samuel Reservoir is a multi-purpose reservoir for the nearby residents. However, the ever-intensifying anthropogenic activities in the catchment have increased the potential pollutants of these reservoirs. Of all the contaminants, heavy metals are non-degradable, can bio-magnify along the food chain and are probably toxic to humans and aquatic biota. Therefore, there is a need for continuous monitoring of the pollution levels in the reservoirs as the assessment provides evidence-based data to protect public health. The concentrations of selected heavy metals in water and sediment samples were collected and determined from three sites in each reservoir (Inlet; Site1-S1, Center; Site2-S2 and Outlet; Site3-S3) for three (3) consecutive months (April to June 2018). Physicochemical parameters (DO, temperature, EC, and pH) were measured at the established three sampling sites using portable Multimeter, while turbidometer was used to measure turbidity. The collected water and bottom sediment samples were analyzed by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) for selected heavy metals (Cu, Zn, Mn, Cr, Cd, Hg, Pb, and As). The data generated from the present study were statistically analyzed using Analysis of Variance (ANOVA). Physicochemical parameters except for temperature in Aba-Samuel Reservoir varied spatially although the differences in their levels among sampling sites were not significant (p>0.05). Among the physicochemical parameters measured in the field, only turbidity surpassed the acceptable limit set for drinking water by different organizations. The mean concentrations of heavy metals in bottom sediments (mg Kg-1) were higher than those in subsurface water samples (mg L-1). The highest concentrations of all metals measured in water and sediment samples were recorded for Mn in both Dire (0.236±0.014, 1098.90 ± 13.25) and Aba-Samuel (0.504±0.023, 1198.39± 6.85) reservoirs, respectively. Mean concentrations of all metals except Mn in water samples of Dire Reservoir were not significantly different among sampling sites (P>0.05), while the reverse was true for those of Aba-Samuel Reservoir. Some heavy metals in sediment samples of both reservoirs (e.g. Mn, Cr, and Pb) showed significant variations (P<0.05) among sampling sites while Zn showed spatial variations, which were not significant (P>0.05). The mean concentrations of heavy metals in water samples were all below the guideline values set by WHO (2008) and USEPA (2011) with the exception of Mn in both Reservoirs and Cd in Aba-Samuel Reservoir. Concentrations of Zn, Mn, Cr, and Cd in sediment samples are, however, above the respective reference values (ISQG, 2002; USEPA, 2010), while those of Pb and Cu were below the respective reference values (ISQG, 2002; USEPA, 2010) in both reservoirs. The results of the present study signify the importance of anthropogenic loading of pollutants and serve as an early signal for the need to take a timely measure to prevent further degradation of the reservoirs. Because the reservoirs are shallow and polymictic, the high concentrations of heavy metals in the sediment can lead to their increased levels in the water column thereby affecting public health and aquatic biota. Therefore, strategies of controlling point and non-point sources located all over the catchment areas should be developed to ensure better protection of the reservoirs, public health, and aquatic and terrestrial life.Item Heavy Metals in Lake Koka Food Chain: Potential Health Risk Implications(Addis Ababa University, 2018-02-04) Tessema, Kassahun; Lemma, Brook (Professer); Fetahi, Tadesse (PhD)The present study was undertaken to investigate heavy metals in Lake Koka (Ethiopia) food chain and its potential health risk implications. Particularly the study examined the concentration of some heavy metals, their bioaccumulation factors in (water, bottom sediments) and their biomagnifications factors along the food chain of phytoplankton-Zooplankton-muscle tissues of fish species. In situ measurements of the physicochemical parameters (DO, Temperature, EC, and pH) were taken from seven sampling sites using portable Multimeter. The major inorganic nutrients (NO3, NO2, NH3, PO4, and TP) were analyzed in the laboratory using APHA method. The heavy metal analysis was performed using Graphite Furnance Atomic Absorption Spectrophotometer method. The results of the study indicated that the values of most of the physical, chemical and biological parameters such as biological oxygen demand (BOD), chemical oxygen demand (COD), Nitrate (NO3) and Chromium (total Cr) were significantly higher at Modjo downstream site (P<0.05). The general distribution of heavy metals in sediment samples was ranked as Mn>Cr >Pb>Zn>Cu>Ni>Cd. Metal concentration in the muscle tissue of fish decreased in the sequence of Cr>Cu>Pb>Cd. Bioaccumulation factor of water for Cd and Pb increased as follow phytoplankton > Zooplankton > fish species. The Biomagnifications factor of Chromium for zooplankton, C. garipinus, O. niloticus and C. carpio are 1.63, 1.18, 1.36, and 2.28 respectively. The concentration of Cr was in the direction of fish species >Zooplankton> phytoplankton. The concentration of Cr at Modjo Upstream, Modjo Downstream, and Kentare sites were above the permissible limits. Similarly, the concentration of Pb at the riverine sites was above the permissible limits of WHO and USEPA prescribed. The concentration of Cr on C. garipinus, O. niloticus, and C. carpio was above the permissible Limits of WHO and FEPA. BAFW for (Cd, Pb and Cr) >1) and BAFS for the same metals <1 indicated that in the study lake there was bioaccumulation from water than sediment. Human exposure to heavy metals due to fish consumption from Lake Koka was also assessed. The results show that weekly intake estimates are considerably lower than the provisional tolerable human weekly intake values provided by WHO and FSA. Thus Cd, Pb, and Cu pose no public health hazard through consumption of the respective fish species. But no tolerable human intake values for Cr from food are provided by the organization, maybe because Cr is not very toxic when introduced by the oral route.Item Key Drivers of Water Quality in Dire and Legedadi Reservoirs, Ethiopia(Addis Ababa University, 2019-06-06) Tilahun, Helnata; Kifle, Demeke (PhD); Fetahi, Tadesse (PhD)Dire and Legedadi reservoirs are the most important freshwater bodies used as surface water sources for the city of Addis Ababa. They are however, facing pollution problem owing to their establishment near fast-growing towns, industrial activities, and intensification of agriculture and the associated application of fertilizers within their catchment areas. Information on physicochemical and biological parameters of the reservoirs is required to manage their living resources and determine their suitability for drinking purpose. In this study, the seasonal and spatial dynamics of physicochemical and biological water quality parameters were therefore, investigated at monthly intervals during 5 months and 2 months of 2018 at three study Sites (Sites 1, 2 and 3) in Dire and Legedadi reservoirs, respectively. All physicochemical and biological parameters were determined with standard methods. Both reservoirs were characterized by unusually high turbidity (19.43-657NTU) throughout the study period mainly due to sediment input through runoff and wind-induced re-suspension of sediment particles. Water transparency of both study reservoirs was extremely low and showed seasonal variations with mean values ranging from 7.2 to 7.6cm (Dire Reservoir) and 4 to 6.5cm (Legedadi Reservoir). The values of water temperature recorded in the present study varied between 15.7 and 21oC. The pH in both study reservoirs was nearly alkaline (6.23-9.2) for most of the sampling months. Higher values were recorded for the concentration of most of the inorganic algal nutrients indicating the nutrient enrichment. Although TDS values were within the range that drinking water should have, high values were recorded throughout the study period. The unusually high turbidity (low water transparency) seems to be the major cause for the deterioration of the water quality in the reservoirs. The phytoplankton community was constituted by five taxa (Cyanophyceae, Chlorophyceae, Bacillariophyceae, Euglenophyceae, and Cryptophyceae) comprising 30 spp. with the dominance of Cyanophyceae including Microcystis aeruginosa, which are associated with public health risk. The zooplankton community comprised three major taxa (Rotifers, Copepods, and Cladocerans, consisting of 20 spp.) with copepod dominance. In general, the hypereutrophic condition in both reservoirs, which was suggested by the estimated TSI values, is indicative of the fact they are suffering from water quality deterioration associated primarily with the high turbidity and nutrient enrichment linked to human disturbance. In addition, the estimated WQI values placed Dire (57.6-73.65) and Legedadi (39.14 - 43.78) reservoirs under the categories of medium and bad water quality, respectively. The results of the present study seem to suggest the urgency of the need to develop workable strategies of restoration and protection from further degradation of the water quality of both reservoirs through catchment-based management since they together cover about 80% of the water demand of the capital and minimize the cost of water treatment and from the results of the present study a year round (seasonal) study is recommended in order to have a full information on the limnology of those reservoirs.Item Partial Replacement of Fish Meal by a Mixture of Lupin (Lupinus Albus L.) and Grass Pea (Lathyrus Sativus L.) Meal in the Diets of Nile Tilapia (Oreochromis Niloticus L.) Fingerlings in a Recirculating Aquaculture System(Addis Ababa University, 2020-06-06) Fisseha, Tsegay; Geremew, Akewake (PhD); Fetahi, Tadesse (PhD)Aquaculture is one of the fastest-growing animal production sectors in the world producing near half (47%) of the world total fish production. However, it depends heavily on the expensive fish meal which is a limiting factor for the formulation of optimal fish diet in aquaculture systems. Although several investigators have tried to replace the fish meal with different locally available sources of plant proteins, similar studies on incorporating a mixture of lupin and grass pea meal are non-existent. This study evaluated the effects of fish meal replacement by a mixture of lupin and grass pea meal at inclusion levels of 0, 25, 50, and 75% as potential plant protein sources in the diets of Nile tilapia fingerlings on growth performance, feed utilization, carcass composition, and hematological parameters. The study was carried out in the Center for Aquaponics and Recirculating Aquaculture System, in the College of Natural and Computational Sciences, Addis Ababa University from October, 2019 to December, 2019 for 10 weeks. Experimental diets were formulated to be iso-nitrogenous (36g 100 g-1), iso-lipidic (10g 100 g-1) and iso-energetic (18 KJ g-1), and fed at 6-10% of their body weight day-1. A total of 276 Nile tilapia fingerlings were stocked into four treatments, each in three replicates using a completely randomized design where different dietary treatments were randomly assigned to the experimental aquaria. At the end of feeding trials, results revealed that replacement of 25, 50, and 75% of fish meal by lupin and grass pea mixture meals did not significantly (P > 0.05) affect most of growth and feed utilization parameters. However, fish fed with 25% lupin and grass pea mixture meal revealed enhanced final body weight and improved feed intake. This enhanced growth performance of fingerlings might be attributed to the compensatory effects of mixing plant proteins that improved the amino acid profile and bioavailability. Compared to the control diet, increasing lupin and grass pea mixture meals in the diets significantly increased hepatosomatic index. This might have been associated with higher feed intake and the high energy content in the feed that resulted in increased storage of glycogen or lipid in the liver. Replacement of fish meal by lupin and grass pea mixture meal has also resulted in comparable carcass composition and hematological parameters. These comparable and promising results might have been because of the improved amino acid profile due to the effect of mixing feed ingredients, and reduced antinutritional factors in the experimental diets due to preprocessing of lupin and grass pea by soaking, dehulling, and roasting. However, Hemoglobin, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration and lymphocytes had shown significant increase at higher fish meal replacement levels (75%). From the economic point of view, lowest incidence cost (44.31) and higher profit index (1.58) was obtained in the 75% replaced diet, whereas highest incidence cost (72.5) and lowest profit index (0.96) was recorded from the control diet. In general, there are promising nutritional and economic justifications for replacing fish meal by a mixture of lupin and grass pea protein sources in the diets of Nile tilapia considering growth parameters, feed utilization, carcass composition, hematological parameters, and economic analysis up to 75% level.Item Some Biotic and Abiotic Factors Affect Phytoplankton Functional Groups in Lake Hawassa, Ethiopia(Addis Ababa University, 7/7/2020) Beyene, Getacher; Kifle, Demeke (PhD); Fetahi, Tadesse (PhD)The water quality of Lake Hawassa has been deteriorated due to high influent load from various sources, including effluents of a hospital, industries, hotels, and agricultural runoff, which can induce changes in phytoplankton functional groups (FGs). The functional association of algae can also be affected by the dominant zooplankton and macrophytes coverage. FGs are groups of phytoplankton species with similar ecological requirements. The FGs approach has greater effectiveness than the taxonomic method in detecting the changes in phytoplankton assemblages in relation to the predominant environmental stressors. No previous study has however been conducted on the FGs in the lake. It was hypothesized that the introduction of pollutants through the various influents of the lake and the composition and abundance of the major zooplankton groups, and the presence of Echichloa pyramidalis (emergent macrophyte) influence the FGs. The main objective of this study was, therefore, to document scientific information on the variations of phytoplankton FGs in relation to these ecological factors in Lake Hawassa, Ethiopia. Sample collection and insitu measurements of physico-chemical parameters were made monthly (April to August in 2019) from four sites. Data analyses were performed using SPSS version 20 and CANOCO version 4.5. A total of 130 species of phytoplankton were identified and classified into 18 trait-based functional groups (RFGs) and 6 morphology-based functional groups (MBFGs). SN, M, P, J, and LO were the most dominant FGs contributing for 91.17% of the total fresh weight biomass of the RFGs. III, IV, V, VI and VII, which accounted 99.0035% of the total fresh weight biomass, were the most conspicuous MBFGs. RDA analysis indicated that the RFGs SN, Lo, M, F, N, J, P, MP and D and the MBFGs III, V, VII, IV and VII were correlated significantly with electrical conductivity, DO, pH, TSS, turbidity, Secchi depth and total phosphorus (P ≤ 0.004) revealing the overriding importance of these parameters in influencing the variation of the phytoplankton FGs in Lake Hawassa. The potentially toxigenic FGs were dominant at the Macrophyte zone due to their preference for shading and water column stability. Rotifers and cyclopoid copepods were the dominant zooplankton taxa with no significant impact on the FGs. The results of this study supported our hypothesis that the biotic (the macrophyte Echinochloa pyramidalis) and the human-induced abiotic (the influents associated) factors have significant impact on the phytoplankton FGs. But, further research is mandatory to better understand the underlying mechanisms governing their interactions. The current study can have practical importance to efforts directed towards improving the water quality of the lake and may also serve as base-line information for further studies.Item Some Biotic and Abiotic Factors Affect Phytoplankton Functional Groups in Lake Hawassa, Ethiopia(Addis Ababa University, 2020-07-07) Beyene, Getacher; Kifle, Demeke (PhD); Fetahi, Tadesse (PhD)The water quality of Lake Hawassa has been deteriorated due to high influent load from various sources, including effluents of a hospital, industries, hotels, and agricultural runoff, which can induce changes in phytoplankton functional groups (FGs). The functional association of algae can also be affected by the dominant zooplankton and macrophytes coverage. FGs are groups of phytoplankton species with similar ecological requirements. The FGs approach has greater effectiveness than the taxonomic method in detecting the changes in phytoplankton assemblages in relation to the predominant environmental stressors. No previous study has however been conducted on the FGs in the lake. It was hypothesized that the introduction of pollutants through the various influents of the lake and the composition and abundance of the major zooplankton groups, and the presence of Echichloa pyramidalis (emergent macrophyte) influence the FGs. The main objective of this study was, therefore, to document scientific information on the variations of phytoplankton FGs in relation to these ecological factors in Lake Hawassa, Ethiopia. Sample collection and insitu measurements of physico-chemical parameters were made monthly (April to August in 2019) from four sites. Data analyses were performed using SPSS version 20 and CANOCO version 4.5. A total of 130 species of phytoplankton were identified and classified into 18 trait-based functional groups (RFGs) and 6 morphology-based functional groups (MBFGs). SN, M, P, J, and LO were the most dominant FGs contributing for 91.17% of the total fresh weight biomass of the RFGs. III, IV, V, VI and VII, which accounted 99.0035% of the total fresh weight biomass, were the most conspicuous MBFGs. RDA analysis indicated that the RFGs SN, Lo, M, F, N, J, P, MP and D and the MBFGs III, V, VII, IV and VII were correlated significantly with electrical conductivity, DO, pH, TSS, turbidity, Secchi depth and total phosphorus (P ≤ 0.004) revealing the overriding importance of these parameters in influencing the variation of the phytoplankton FGs in Lake Hawassa. The potentially toxigenic FGs were dominant at the Macrophyte zone due to their preference for shading and water column stability. Rotifers and cyclopoid copepods were the dominant zooplankton taxa with no significant impact on the FGs. The results of this study supported our hypothesis that the biotic (the macrophyte Echinochloa pyramidalis) and the human-induced abiotic (the influents associated) factors have significant impact on the phytoplankton FGs. But, further research is mandatory to better understand the underlying mechanisms governing their interactions. The current study can have practical importance to efforts directed towards improving the water quality of the lake and may also serve as base-line information for further studies.