Natural and Applied Sciences

Juvenile Nile tilapia (12.05 :1:0.67 g) were exposed for 10 weeks to a stable, sublethal concentration (0.313 mL L-1) of water soluble fractions of the Bonny Light crude oil. A significant decrease in leucocytes, erythrocytes, haematocrit, haemoglobin, and mean corpuscular volume were observed, indicating an anaemic response. Also a hyperglycaemic response, as indicated by significantly raised plasma glucose in the exposed fish, was observed. The causes of alteration in these blood parameters and their environmental implications are discussed.

This study examined the long-term effect of a common aquaculture antibiotic, oxytetracycline, o n several blood parameters of the Nile tilapia Oreochrornis niloricus under laboratory conditions. The fish were fed daily on isocaloric (24.56 ? 0.96 J/mg gross energy) and isonitrogenous (38.89 ? 0.08% crude protein) diets incorporated with varying concentrations of the drug (5.00, 2.50, 1.25 and 0.63%) for 8 wk. A control diet with no oxytetracycline was fed to another group of fish. Significant reductions in leukocyte, erythrocyte, thrombocyte, hematocrit, and hemoglobin values were observed, the reductions being directly proportional to the concentrations of the drug in the diet, indicating an anemic response. Though the use of oxytetracycline in aquaculture can be beneficial, the results from this investigation suggest that the drug may have some level of interference with the blood chemistry of the fish at therapeutic dosage.

An experiment was conducted to evaluate the effects of different levels of pig dung pond fertilization to test tilapia yield at each level of concentrations. The concentrations used were 8.36, 20.89 and 33.43 g/m /day; for Low Concentration of Pig Dung (LCPD), Medium Concentration of Pig Dung (MCPD) and High 3

As a part of its efforts to contribute to alleviation of food insecurity, hunger and poverty, this study was conducted to investigate the performance of the cichlid, Oreochromis niloticus (Linnaeus) fed varying levels of processed sweet potato (Ipomea batatas) peels. The varying levels of sweet potato peel in the different experimental diets were 0, 5, 10, 15, 20 and 25% (all diets were iso-nitrogenous -31.23 ± 0.22% crude protein). Twenty mixed-sexed fingerlings of the experimental fish (mean weight 0.47 ± 0.01 g) were fed the different diets for a period of 10 weeks in triplicates. The greatest increase in body weight (1.30 ± 0.07 g) of the fish was achieved with the control diet (P < 0.05), this was followed by the fish fed diet with 5% of the peel (0.90 ± 0.06 g) while the least increase in body weight (0.46 ± 0.01 g) was obtained in the fish fed diet with 25% of the peel (P < 0.05). Similarly, the best specific growth rate (SGR) and apparent digestibility were obtained in the fish fed the control diet, while the fish fed with diet containing 25% of the peel recorded the least SGR and apparent digestibility. Analysis of the results of plasma glucose and plasma protein revealed that there were no deleterious effects recorded in the test fish due to the dietary inclusion of the sweet potato peel. Analysis of the results revealed that Oreochromis niloticus could tolerate up to 15% level of inclusion of sweet potato peel. The significance of this research finding is that sweet potato peels can be incorporated into fish feeds in order to reduce the cost associated with production of farmed fish, as a part of efforts to contribute to alleviation of food insecurity, hunger and poverty in several rural communities in the world with special reference African countries.

An experiment was conducted to evaluate the effects of different levels of pig dung pond fertilization to test tilapia yield at each level of concentrations. The concentrations used were 8.36, 20.89 and 33.43 g/m /day; for Low Concentration of Pig Dung (LCPD), Medium Concentration of Pig Dung (MCPD) and High 3

Juvenile Labeo senegalensis (Cyprinidae) mean weight: 0.35 ± 0.02 g, were fed moist isonitrogenous and isocaloric diets incorporated with varying levels of veterinary graded oxytetracycline; 5,2.5, 1.25, 0.625 and 0% (control) over a 6-week period under laboratory conditions. Survival, growth performance and feed utilization of the fish were studied. Survival in all fish groups was above 90% with the exception of the group fed 5% oxytetracycline incorporated diet. At incorporation levels of 5, 2.5 and 1.25% oxytetracycline, there was significant (P < 0.05) reduction in growth performance compared to 0.625 and 0%. The feed efficiency and protein efficiency ratios were adequate (below 0.9 and above 2 respectively) with the exception of fish fed the 2.5 and 5% incorporated diets. The apparent protein digestibility was above 90% in all diets, with the exception of the 5% incorporated diet which resulted in significant reduction (P < 0.05). Proximate composition of the fish carcass indicated that there was no significant differences (P > 0.05) in the tissue protein and lipid of the control fish and group fed diets incorporated with 1.25 and 0.625% oxytetracycline. The implications of this drug in growth performance in Labeo senegalensis are discussed.

The acute toxicity of water extracts of the barks of two molluscicidal and piscicidal plants, Balanites aegyptiaca and Kigelia africana, to the Nile tilapia, Oreochromir niloticus (L.), was investigated using static bioassays and continuous aeration over a period of 96h. The 96h LCs1, opercular ventilation rates and tail beat frequency were determined. Extract of B. aegyptiaca was observed to be more toxic than that of K. africana. Opercular ventilation and tail fin beat increased sharply with exposure to both extracts and then declined as the fish became fatigued. Death is believed to be due to both fatigue and direct toxic effects of the plant extracts on the fish tissues.

A comparative study of the gut helminths of Tilapia zilli and Clarias gariepinus from river Uke in Plateau State, Nigeria was carried. A total of 100 fishes comprising of 60 T. zilli and 40 C. gariepinus were examined for helminth parasites. The parasites encountered include Camallanus ...

The acute toxicity of alkylbenzene sulphonate (ABS) detergent to the toothed carp. Aphyosemion gairdneri (L.). was investigated using static bioassays and continuous aeration over a period of 96 h. The 96-h LC,^, opercular ventilation rates per minute and behaviourial responses were evaluated. The 96-h LC was determined to be 25.11 ± 8.4 mg 1"'. The toxicant led to an initial increase in the opercular ventilation, which then decreased below the initial values by the 96th hour of exposure. Prior to death, erratic swimming, lost of balance and respiratory distress were observed. Skin lesions and haemorrhaging of the gill filaments were observed on dead fish.

In the present study, utilization and nutrient digestibility of mango seeds and palm kernel meal by juvenile Labeo senegalensis (Antheriniformes: Cyprinidae) were investigated under laboratory conditions. The two ingredients were incorporated at separate levels of 0%, 10%, 20% and 30%. The feeding period lasted for 12 weeks. In general, best growth and feeding performance was obtained with the control diet (0% of mango seeds and palm kernel meal), but results were not signi®cantly different (P > 0.05) from those obtained with the 10% palm kernel meal inclusion level. Weight gain of ®sh fed all diets was above 120%. With the exception of the 20% and 30% mango seed inclusion level, the speci®c growth rate (SGR) of the ®sh was above 1% day ±1. The protein productive values were not signi®cantly (P > 0.05) different between the experimental diets. Protein and carbohydrate digestibility was above 86% and 45%, respectively, in all diets. Proximate composition of ®sh carcass, hepatosomatic index, liver glycogen and plasma glucose after the feeding trials revealed no evidence of nutritional pathology. It was concluded, that at appropriate levels, palm kernel meal and, to a lesser extent, mango seeds can be incorporated into diets of juvenile L. senegalensis without signi®cant depression of growth and health of the ®sh.

The effect of petroleum effluent pollution on the plasma glucose, liver and muscle glycogen of the Nile tilapia, Oreochromis niloticus (L.) were investigated. The results obtained shows evidence of stress and impairment of carbohydrate metabolism in fish obtained from down stream of the polluted river. The affected fish showed hypoglyca~mic response and liver and muscle glycogen depletion.

The effects of substituting cottonseed meal (CSM) for groundnut meal (GNM) on growth, food conversion ratio and protein efficiency ratio of the toothed carp, Aphyosemion gairdneri (mean weight: 0.1017  0.0077 g) was investigated under laboratory conditions (mean dissolved oxygen: 18.88  0.03 mg/l; was temperature: 22.69  0.51). The results showed that the best growth and food utilization indices were recorded in fishes fed 30% CSM and 10% GNM diet. While the poorest growth and feed utilization indices were recorded in the fish fed 15% CSM and 25% GNM diet. There was no significant difference between the amino acid profiles of the various diets. The CSM can be conveniently substituted for GNM in the diet of toothed carp at 30% of the total composition of fish diets, thereby reducing the cost of the feed without compromising on the fish growth.

A comparative study of the gut helminths of Tilapia zilli and Clarias gariepinus from river Uke in Plateau State, Nigeria was carried. A total of 100 fishes comprising of 60 T. zilli and 40 C. gariepinus were examined for helminth parasites. The parasites encountered include Camallanus sp., Crepedostomum meteocus, Procamallanus laeviconchus, Proteocephalid sp., and Sphaerostoma bramae. A total of 61% of the T. zilli were found to be infected with one parasite or the other while 55% of C. gariepinus were infected. Chi-square test confirmed a significant difference (P < 0.05) in infection rate between the two species, although no significant difference was observed between the males and females of the two different fish species.