Veterinary Medicine
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Item Size variation, growth and body conformation of reciprocal hybrids of Clarias gariepinus (Burchell 1822) and Heterobranchus bidorsalis (Geoffroy, 1809).(Nigerian Institute for Oceanography and Marine Research, 1996) Uka A.; Oladosu G. A.; Ayinla O. A.Reciprocal hybrids of Clarias gariepinus and Heterobranchus bidorsalis were compared for size variation, growth and body conformation. Growth was observed to be significantly faster (P<0.05), and size variation less pronounced (CV = 26%) for C. gariepinus (female) and H. bidorsalis (male) hybrid, than the reciprocal (CV=38%) No difference was observed in the body conformation between the reciprocal hybrids. However, the percent head length of the standard length was significantly smaller (P<0.05) in the reciprocal hybrids than that observed for the parent species.Item Morphometric and blood group characterization of different populations of Clarias gariepinus(Faculty of Agriculture, University of Benin, Nigeria, 2004) Uka A.; Ayinla O. A.; Oladosu G. A.Experiments were conducted to compare the blood group antigen and morphometric features of three populations of Clarias gariepinus described according to the source of their farmed parents as ARAC, Holland and Osogbo. Differences in morphometric features were studied in three replicates of 50 individuals per replicate grown in earthen pond for 150 days, while Blood group antigen differences were studied on slide agglutination test using human antisera. The fish were fed twice daily with 22% crude protein feed. Feeding ration was gradually reduced from 20% body weight in the first 30 days to 5% body weight at day 121 to 150. Water temperature, pH and dissolved oxygen were determined two days in a week between 9am and 11am. The three populations differed significantly (P<0.05) from each other in the prepelvic ratio of the standard length, but showed common morphometric features in the head length and head width ratios of the standard length and the proportion of the standard length to the total length. However, the proportion of intra-orbital width of the standard length was significantly lower (P<0.05) in Osogbo population than in ARAC and Holland populations, while the proportion of the prepectoral distance of the standard length was significantly lower (P<0.01) in Holland population than ARAC and Osogbo population. There was no difference in the red cell agglutination test among the populations; agglutination characteristic of blood group O' rhesus negative was observed in all the individuals of the three populations. Differences in water quality parameters were not significant (P>0.05). Values obtained ranged from 27.50 to 27.87°C, 6.55 to 7.56 and 5.68 to 7.70mg/l for temperature, pH and Dissolved oxygen respectively.Item Predation by aquatic insects on African catfish fry(Chapman & Hall, 1997) Adeyemo A. A.; Yakubu, A. F.; Oladosu G. A.; Ayinla O. A.Item Environmental induction of natural spawning in Gymnarchus niloticus (Cuvier 1829) in earthen pond(Blackwell Science, 1997) Oladosu G. A.Item Efficacy of silt and powdered milk in the removal of stickiness of fertilized eggs of Clarias gariepinus(Faculty of Agriculture, University of Benin, Nigeria, 2004) Oladosu O. O.; Oladosu G. A.; Yakubu A. F.Two batches of Clarias gariepinus eggs each were treated with autoclave-sterilized silt (25ml/L of water) and powdered milk (18g/L of water) respectively for 45minutes prior to incubation. A third batch of eggs that was not treated was incubated immediately after fertilization to serve as control. The three water quality parameters observed for all the treatments including temperature, dissolved oxygen and pH are within acceptable limits for Clarias gariepinus. They range from 26.7° C to 26.8°C for temperature, 5.9mg/L to 6.1mg/L for Dissolved Oxygen and 6.9 to 7.4 for pH. Hatching rates and the percentage of eggs that were free (unattached) were observed to be significantly highest in the batch treated with silt, which recorded 60.55% free eggs and 64 % hatching rate, as compared to the batch treated with powdered milk which recorded 22.0% free eggs and 38% hatching rate. The control (untreated) also recorded 10.2% free eggs and 32.6% hatching rate. This observation showed that silt is a more effective de-adhesive agent in the control of stickiness of fertilized C. gariepinus eggs and an indication that silt particles may not have adverse effect on the hatching of eggs.Item Investigating suitable fish food sources for hatchery rearing of Gymnarchus niloticus (Curvier 1829) Fry(Faculty of Agriculture, University of Benin, Nigeria, 2002) Oladosu G. A.; Oladosu O. O.Analysis of the stomach content of 20 six week-old fry of Gymnarchus niloticus spawned in an earthen pond and nursed in situ, revealed the presence of three major groups of aquatic organisms namely algae, zooplankton and insect larvae. Observations on the frequency of occurrence of items in the stomach content showed that only Brachionus sp. (zooplankton) and Cryptochironomus deribae (insect larva of the family Chironomidae) were present in all the stomachs examined. The percent composition by number of the items indicated that C. deribae is the most predominant, followed by the Brachionus sp. This suggests that C. deribae is preferred to other first food sources available in the earthen pond. However, the next most predominant item in the stomach contents; Brachionus sp., which is more readily cultivable, will better serve the purpose of hatchery rearing of the fry of G. niloticus, as first food.Item Influence of salinity on the development stages of African catfish (Clarias gariepinus)(JASEM, 1999) Oladosu G. A.; Busari, A. N.; Uka, A.; Oladosu, A. O. O.; Ayinla, O. A.Salinity tolerance was tested in fertilized eggs, yolksad larvae, post yolksac larvae and fingerlings of Clarias gariepimus at 0, 2.5, 5.0, 7.5, 10.0, 12.5 and 15ppt salinity. The highest hatchability was observed in fertilized eggs incubated in 2.5ppt, which recorded 71.8%. This was however not significantly higher than the 66.29% and 65.89% hatchability, recorded for the control group (Oppt) and 5ppt respectively. The median lethal salinity values in 96 hours (MLS-96) obtained for the yollac larvae, post yolksac larvae and fingering stages are; 1.9, 2.2 and 7.8 respectively, demonstrated an ontogenetic variation in salinity tolerance of C. gariepimus. However, salinity tolerance of the fertilized eggs, larvae and fingerlings of C. garlepimus is observed to be generally low, and typically of fresh water stennohaline species. This relatively low salinity tolerance of C. gariepinus has probably prevented its existence in brackish waters. None of these stages are suitable for the transfer of C. gariepimus to brackish water environment for the purpose of commercial fish farming. However, results obtained in this study, could be a guide for the use of salt in the prophylactic and therapeutic control of pathogens sensitive to salt. The salinity tolerance of C. gariepimus is dependent on the developmental stage of the fishItem Isolation and pathogenicity of Bacillus sp. associated with a septicaemic condition in some tropical freshwater fish species(Verlag Paul Parey, Hamburg und Berlin, 1994) Oladosu G. A.; Ayinla, O. A.; Ajiboye, M. O.Observations made over a three-year period at the Fish Diseases Laboratory of the African Regional Aquaculture Centre (ARAC), Nigeria, revealed the gradual emergence of a new, highly infectious septicaemic condition in some widely cultivated freshwater fish species. The broad host range included: Heterobanchus bidorsalis, Clarias gariepinus, “Heteroclarias” (a hybrid of these two species, male and female respectively), Chrysichthys nigrodigitatus, and Cyprinus carpio. Clinical signs and pathological lesions associated with the condition were typical, irrespective of the fish species affected; natural out- breaks ap eared to be associated with stress &e to environmental factors. The bacterium isolated from moribuncf and freshly-dead fishes was identified as a Bacillus sp., based on the observed cultural, morphological and biochemical characteristics. Fish reinfection trials confirmed that the isolate was the causative agent of the condition. Antibiotic sensitivity tests showed that the organism was sensitive to tetracycline hydrochloride.Item Aetiology, epizotiology and pathology of ‘rusty yellow’ skin discolouration of tilapia species Oreochromis niloticus and Tilapia zilli(Blackwell Wissenschafts-Verlag, 1994) Oladosu G. A.; Ayinla, A,; Ajiboye, M. O.The presence of a rusty-yellow discolouration of the skin of the two tilapia species being cultured at the African Regional Aquaculture Centre (ARAC) was studied using clinical and epizootiological methods. The condition affected the tilapia species only. Ante-mortem and post-mortem examination revealed that the discolouration was restricted to the surface of the cutaneous tissue; affecting the underside of the exposed part of the scales, the fins, and the skin flap covering the scale pockets, mostly in adult fish. Microbiological and histopathological studies, as well as experimental infection trials demonstrated that a rosette-shaped, filamentous gram-positive bacterium, was the aetiologic agent. This organism was characterised as an Actinomyces species based on standard microbiological techniques. Correlation between physico-chemical parameters of the pond water and the prevalence of the skin discolouration, suggested a possible relationship to low dissolved oxygen. The prevalence of the skin discolouration was observed to increase over the 4-month culture period, being somewhat greater in a non-integrated than in an integrated culture system at harvest. Efforts to control the condition with available chemotherapeutics (mostly disinfectants and antibiotics) were ineffective although the organ- ism was observed to be sensitive to terramycin.Item Design and construction of a shrimp hatchery for the breeding of the black tiger shrimp Peneaus monodon(Fisheries Society of Nigeria, 2009) Ayinla O. A.; Anyanwu P. E.; Atakpu J. A.; Ebonwu B. I.; Hamzat M. B.; Ihimekpen F. A.; Oladosu G. A.; Adeleke T. A.; Matanmi M. A.; Afolabi E. S.; Oguntade O. R.; Ayaobu-Cookey I. K.; Asikhia G. I.; Oseni A.; Olaluwoye L. B.; Ajijo M. R.A shrimp hatchery for the breeding of the black tiger shrimp, Penaeus monodon was constructed the Nigeria Institute for Oceanography and Marine Research in 2008 by the reconstruction of an existing old shrimp hatchery. The new shrimp hatchery comprises of the following: water treatment, water storage, broodstock maturation, spawning/incubation, nursery and micro-algae units. The design included the construction of a concrete sump for the collection and treatment of wastewater before disposal, in addition to an acration unit equipped with root blower for adequate supply of dissolved oxygen. The reconstructed NIOMR shrimp hatchery has been successfully used for the production of post larvae, which are presently being reared to adult shrimp in concrete tanks. The successful completion of the shrimp hatchery and breeding of P. monodon has confirmed that the species can be spawned and reared to adult size in Nigeria for local and export markets.