College of Natural and Computational Sciences

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Subject: search.filters.subject.O. niloticus

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    INFESTATION AND EFFECTS OF ANISAKID NEMATODE PARASITES ON THE NILE TILAPIA (Oreochromis niloticus LINNAEUS, 1758) IN LAKE HAWASSA, ETHIOPIA
    (HAWASSA UNIVERSITY, 2024-10) RIBKA MENTA BALCHA
    Contraceacum species that is genus of Anisakid parasites is the most economically important internal fish parasite,that poses serious problem in culture and capture fisheries globally, as well as consumers. This investigation aimed to evaluate the infestations and certain effects of Contraceacum spp. on O. niloticus L. 1758) in Lake Hawassa. The study used a cross-sectional design from December 2023 to May 2024. A total of 180 O. niloticus were taken from the landing site. To assess the water quality, samples of water were taken fro amora gedel. Infestation peaked in February and April each with 56.6% and lowest in December (40.0%). However, highest intensity of Contracaecum spp. was in May (9.66%) and lowest in January with (4.20%). Prevalence of Contracaecum with sex of O. niloticus were statistically not significant.The size of O. niloticus and the presence of Contracaecum were positively correlated. Hematological effects of Contracaecum on O .niloticus between infested and non-infested group were significant (p<0.05) except for neutrophil count sand basophil (p>0.05). The results of the physicochemical parameters showed statistically significant difference with all parameters except ammonia that showed variation, but not statistically significant (p value=0.294). There were positive correlation between physicochemical parameters and the prevalence of Contracaecum, however, negative correlation with dissolved oxygen (r=-0.002). In conclusion, the temperature of the water influences whether the Contracaecum infestation is high or low, depending on the sampled months. Contracaecum parasite prevalence is also influenced by variations in physicochemical parameters. The high prevalence (37.3%) of Contraceacum spp. in muscles of O. niloticus as compared to varied various body organs indicates that consuming raw fish poses a significant health risk to humans. Therefore,it is crucial to eat the fish only well coocked form, at the encysted larvae present in fish muscle can be transmitted to human hosts.
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    REPRODUCTIVE BIOLOGY AND FEEDINDG HABITS OF THE NILE TILAPIA OREOCHROMIS NILOTICUS (L. 1758) (PISCES: CICHLIDAE) IN DAMTE DAM, WOLAITA ZONE SOUTHERN ETHIOPIA
    (HAWASSA UNIVERSITY, 2024-10) ERMIAS SHIRKO BIRBIRE
    Reproduction, feeding and condition factor of O. niloticus were investigated in Damte Dam based on the samples collected from February, 2024 to September, 2024. A total of 584 fish samples were caught ranging from 10 cm to 33.9 cm TL and 32 g to 750 g TW for males and 9.7 cm to 33.9 cm TL and 32.1 g to 421 g TW for females. The aim of this study was to investigate reproduction and feeding habits of O. niloticus in Damte Dam, Ethiopia. The overall male to female sex ratio was significantly different from 1:1 (ꭓ2=4.281, p<0.05). Lm50 for males and females were 14.7 cm TL and 13.9 TL cm, respectively. GSI values ranged from 0.26 to 1.59 for males and 0.25 to 1.8 for females. The fish bred throughout the sampling period with intensive breeding months in May, June and July. The length weight relationship was found to be curvilinear (TW = 0.0105TL3.1988). ACF value of male was minimum values of 0.40 to maximum value of 2.99 with a mean of 0.933 ± 0.013 and females O. niloticus ACF was ranged from 0.75 to 2.77 with mean value of 1.39 ± 0.016. Detritus (94.61%, 34.53%), macrophytes (88.41%, 29.59%), phytoplankton (85.18%, 31.36%), insects (18.33%, 2.61%) and zooplankton (11.59%, 1.90%) were using frequency of occurrence and volumetric analyses respectively. In general, ACF and ripe gonad were inversely proportional, and compared to other studies. The fecundity of O. niloticus in Damte Dam was relatively low. There was no observable variation in the food items between dry and wet months, but notable ontogenetic variation was seen in the diet. O. niloticus under 15 cm TL should be protected to save the breeding fish from the risky fishing of locals. The study emphasizes the importance of raising public awareness about the value of using fisheries resources to improve local communities' living standards and research on Damte Dam conservation
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    EFFECTS OF PROBIOTIC SUPPLEMENTATION ON GROWTH AND HEALTH PROMOTION OF THE NILE TILAPIA, Oreochromis niloticus (Linnaeus, 1758)
    (HAWASSA UNIVERSITY, 2023-10) KASSAHUN KOYSHA OYATO
    Probiotics have emerged as promising feed additives in aquaculture, offering potential benefits for fish growth and health promotion. This study was intended to evaluate the efficacy of three probiotic strains, Bacillus subtilis subtilis (p1), Bacillus subtilis inaquosorum (p2), and Saccharomyces cerevisiae (p3), on the growth and health of Oreochromis niloticus fingerlings. A total of 300 fingerlings with an average weight of 7.7 ± 0.103g and length of 7.46 ± 0.073cm were randomly divided in to five experimental groups: control (p0), p1, p2, p3, and a combination of all three probiotics (p4). The fish were fed a diet containing 30% crude protein (CP) at 5% of their body weight either with a basal feed (control group, p0) or with probiotic-supplemented feed (p1, p2, p3, and p4 groups at a dosage of 1.5*10⁸ CFU/mL) for 90 days. Water quality parameters, including dissolved oxygen (DO), pH, and temperature, were measured every 15 days, three times a day. Growth performance parameters, including body weight gain (BWG), specific growth rate (SGR), daily weight gain (DWG), feed conversion ratio (FCR), protein efficiency ratio (PER), and survival rate (SR), were assessed at the end of the experimental period. Additionally, gut microbiota analysis, hematological parameters, and proximate composition of fish were evaluated. The results indicated that water quality parameters remained stable throughout the experiment, except for DO, which showed significant differences (P < 0.05) among the groups. The probiotic-supplemented groups (p1, p2, p3, and p4) exhibited significantly higher growth performance parameters compared to the control group (p0). The group fed with Bacillus subtilis inaquosorum (p2) demonstrated the most remarkable growth performance, with the highest BWG (128.4 ± 0.146 g), SGR (2.66 ± 0.015% day⁻¹), DWG (1.43 ± 0.001 g day⁻¹), and PER (4.28 ± 0.004), and the lowest FCR (1.04 ± 0.003) and SR (100 ± 1.291%). Additionally, the probiotic diet effectively eliminated pathogenic microflora, including Salmonella spp., Escherichia coli, and Candida albicans, from the gut of O. niloticus compared to the control group. Hematological examination revealed significantly improved packed cell volume, RBC, hemoglobin, WBC, and differential leukocyte counts in the probiotic-fed groups. Proximate composition revealed better Crude protein, Dry matter and Carbohydrate content in probiotic diet and decreased Moisture, Crude fat, Ash and Crude fiber. In conclusion application of probiotics in aquaculture is crucial to improve growth and health of O. niloticus as well as to improve water quality
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    INFLUENCE OF WATER QUALITY ON PARASITE PREVALENCE IN NILE TILAPIA (Oreochromis niloticus Linnaeus, 1758) IN CULTURE SYSTEMS IN SIDAMA REGION, ETHIOPIA
    (HAWASSA UNIVERSITY, 2024-10) BERHANESH ARFICHO BOKORO
    Parasitic infestation can lead to severe retarded growth and mortalities in high intensities in fish under culture systems. Importantly, the quality of water in the culture facility may influence the parasitic infestation. This study aimed to evaluate the influence of water quality on parasite prevalence in Nile tilapia, Oreochromis niloticus L,1758 in culture systems in Sidama Region. The study used a cross-sectional design from December 2023 to May 2024. Water physico-chemical parameters such as temperature, dissolved oxygen, pH and turbidity were measured in situ by following standard procedures. Water samples for nutrient contents such as ammonia, nitrate and nitrite were analyzed. A total of 240 O. niloticus (120 from Kokeb fish farm and 120 from CARE fish farm) were taken and examined in the laboratory for ecto and endo parasites by using stereo zoom dissection microscope. The parasitological aspects such as prevalence, mean intensity and mean abundance were calculated based on standard formulae. The results indicated that, the water quality parameters were significantly different (p<0.05) between both fish farms. The total number of parasite species recorded during the study was 11 species. While Kokeb fish farm showed 11 parasite species, there were only six species in CARE farm. Out of 240 fish sampled, 109 fish were infested representing an overall prevalence of 45.41%, mean intensity of 6.30 and mean abundance of 2.86. The prevalence, mean intensity and mean abundance in Kokeb farm were in the order of 59.16%, 7.46 and 4.41. In CARE farm, it was 31.66%, 4.48 and 1.30 respectively. The infestation showed a statistical difference (p<0.05) between the fish farms. There was a positive correlation between water quality and prevalence of parasite species, except dissolved oxygen. The size of O. niloticus and prevalence of parasite species was positively correlated (r=0.978). Prevalence of parasite species with sex of O. niloticus was statistically significant (x2=2.776, p<0.05). The Fulton’s condition factor of parasitized and non-parasitized O. niloticus showed no significant difference (p>0.05). Hematological effects of parasite species on O. niloticus between infested and non-infested groups were significant (p<0.05) except for neutrophil counts (p>0.05). The prevalence of parasite species was influenced by poor water quality. The study recommends that, to reduce or control parasite infestation in culture systems, there is an imperative need to undertake regular monitoring and management of water quality parameters in fishponds.
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    STUDIES ON THE REPRODUCTIVE BIOLOGY AND FEEDING HABITS OF SOME FISH SPECIES AND DETERMINATION OF SOME PHYSICO-CHEMICAL CHARACTERISTICS OF LAKE BOYO, ETHIOPIA
    (Hawassa University, 2024-11) TAMIRAT HANDAGO SADE
    Lake Boyo is among the few neglected and unexplored small lakes in the Central Ethiopian Rift Valley Region. It is a shallow and turbid lake with surface area of 3.2 square kilometres and surrounded by wetland. Three fish species are known to exist in the lake, namely Nile Tilapia Oreochromis Niloticus (Linnaeus, 1758), the straightfin barb Enteromius paludinosus (Peters 1852) and the lapping minnow Garra quadrimaculata (Rüppell, 1835). Neither fishery activity nor fishery research has ever been conducted so far in Lake Boyo. This research was conducted to provide baseline information on some aspects of the reproductive biology and feeding habits of fish species, and physicochemical characteristics of the lake. All the data for this study were collected and analyzed using standardized methods and sampling techniques. For the analysis of reproductive biology and feeding habits, samples of the three fish species were collected from two sites (littoral and open) of the eastern part of the lake from May 2021 to May, 2022 using gill nets of 6, 8, and 10 cm mesh size and a beach seine of 6 mm mesh size. A total of 379 O. niloticus, 513 E. paludinosus, and 290 G. quadrimaculata samples were examined. The water samples for the analyses of physicochemical parameters were collected from two selected sampling sites (littoral and open water area) in wet months (June to September), and dry months (October to December) of 2022. The three fish species breed throughout the year and showed a bi-modal major and minor breeding period. The first peak breeding months occur from February to March and the second minor peak from July to September for O. niloticus, whereas the main breeding season for E. paludinosus was between October and January with a less pronounced reproductive period between March and April. On the otherhand, the first peak breeding period was from June to September and the second peak from January to February for G. quadrimaculata. The fecundity of O.niloticus ranged from 216 to 1,157 eggs per fish while it ranged from 1,078 to 9,683 eggs per fish for E. paludinosus. The result of length at first maturity (Lm50) depicted that the fishes reached sexual maturity at a smaller size and shows early maturity of all the fish species in the lake. The results of the analysis of sex ratio for the fish species examined showed that the distribution of male and female fishes in the lake was not significantly different from the hypothetical 1:1(Male: Female) ratio for O. niloticus and E. paludinosus (1:0.92, p>0.05 and 1:1.03, p>0.05, respectively), while it was significantly different for G. quadrimaculata (1: 0.73, p<0.05). The results of the length weight relationship (LWR) of the fish species suggested a curvilinear relationship (R2= 0.9911, 0.9812 and 0.9766 for O.niloticus, E. paludinosus and G. quadrimaculata, respectively) and, a positive allometric growth pattern (b= 3.1268 and 3.1042 for O.niloticus, E. paludinosus, respectively) while nearly isometric growth pattern (b= 2.977) for G. quadrimaculata. The result of Fulton`s conditon factor (FCF) for the fish species revealed that O.niloticus and E. paludinosus had moderate body condition (FCF= 1.73 and 1.77 for males and females of O.niloticus, respectively, and 1.21 and 1.27 for males and females of E. paludinosus, respectively), while it was low for G. quadrimaculata (FCF= 0.011 and 0.0112 for males and females, respectively). The feeding habits of the fish species showed that the fishes feed on a variety of food items including detritus, phytoplankton, macrophytes, insects and zooplankton and they are ominivorous in their feeding habits. Detritus was the main food item for the fish species in general. The fishes showed seasonal variations in feeding habits during the dry and wet months. From these results it was concluded that the fishes are omnivorous in Lake Boyo. The results of the physical and chemical features of the lake shows that the lake water was slightly warm, alkaline, contained more TDS and EC, very turbid, low transparency and with relatively high inorganic nutrients (NO3- and PO4 3-) which support most of the aquatic life. Generally, based on the results it is concluded that Lake Boyo is a low productive inland freshwater ecosystem in the Ethiopian Rift Valley basin. The high amount of detritus in the stomachs/guts of the fishes and lower condition factor of the fish with reference to other lakes indicate that productivity of Lake Boyo is low. Further research is recommended on macrophyte, phytoplankton and zooplankton composition, biomass and productivity of Lake Boyo.