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 A comparative study of the reproductive capacity of the African catfish species, Heterobranchus bidorsalis GEOFFROY, Clarias gariepinus BURCHELL and their hybrid “Heteroclarias”(Nigerian Institute for Oceanography and Marine Research, 1993) Oladosu G.A.; Ayinla, A.; Adeyemo, A. A.; Yakubu, F. A.; Ajani, A. A.The female hybrid of Heterobranchus bidorsalis (male) and Clarias gariepinus (female) is not only reproductively viable, it also produces eggs of bigger size than the parent species. The quantity of eggs produced per kilogram body weight is however significantly higher (P < 0.05) and P<0. 01) in Clarias gariepinus. The latter fish species is therefore more fecund than the Heterobranhus bidorsalis and the "heteroclarias". This may be an advantage for the mass production of "heteroclarias" which is already popular with the local farmers for its fast growth, comparable to that of Heterobranchus spp. industry. The catfish species are very popular with fish farmers and consumers, and are therefore very important to the sustainability of the aquaculture industry in the country. However, in spite of the breakthrough reported for the artificial propagation of the African catfish species (Richter et al., 1982, Legendre 1986, Ayinla 1988 Legendre 1988, and Nwadukwe et al 1991), the supply of the seeds especially of Heterobranchus spp. is still a far cry from the demand. This study compares the reproductive capacity of three popular African catfish species that can be cross bred artificially, with the aim to enhance catfish fingerling supply, taking the farmers and consumers preference into consideration.Item Effect of organic fertilization on pond productivity and water quality of fish ponds at Aluu, Nigeria(Nigerian Institute for Oceanography and Marine Research, 1991) Onuoha G.C.; Chinda, A.; Oladosu, G. A.; Ayinla, O. A.The results of an investigation showed that the gross productivity of the integrated ponds gave higher values of 90.00 to 387.50 mgC/m3/hr than the non-integrated system with values ranging from 51.25 to 108.13 mg/m3/hr-1. There were significant differences (P 0.05, SP 0.01) between the integrated and non-integrated system with feeding in terms of primary productivity and chlorophill a phytoplankton density ranged from 10 to 2,000 cells/ml in the integrated treatment much higher than in the non-integrated system. The final individual weight, individual weight gain and recovery rate were best for Clarias gariepinus under Treatment I. Also, C. gariepinus yield in Treatment I was 47.7% of that in Treatment I, while yield between Treatment III was 15.6% and 32.7% of those of Treatments I and II respectively. There was no statistical difference (F≥ 0.010 and F≥0.05) in the mean growth rate and average yield of both fish species in all the treatments. However, there was significant difference in the mean daily growth rate between Treatments I and III only; in the mean yield between Treatments I and II, I and III and II and III respectively. The fish biomass harvested suggested a close relationship between phytoplankton bloom or natural productivity and fish growth. The physicochemical properties suggested that the water quality of the integrated pond system was adequate for greater natural production. Result showed that for most of the time, blooms of phytoplankton kept the water conditions close to that necessary for optimal growth.Item Performance of Clarias gariepinus in a polyculture with Oreochromis niloticus under the integrated broiler chicken/fish farming(Nigerian Institute for Oceanography and Marine Research, 1990) Oladosu G.A.; Ayinla, O. A.; Onuoha, G. C.; Needom, J. GA study of the performance of Clarias gariepinus (African Mudfish) in a polyculture with Oreochromis niloticus (Tilapia), integrated with broiler chicken production. was carried at the African Regional Aquaculture Centre, Nigeria. Three experimental treatments were utilized. Treatment I was a poly culture of C. gariepinus and O. niloticus integrated with broiler chicken production, with application of supple- mental feed to fish. Treatment II was a repeat of treatment I, except that no supple- mental feed was applied to fish, while treatment III was a polyculture of the two fish species per se with application of supplemental feed to fish. Results showed that the final individual weight, individual weight gain and recovery rate were best for C. gariepinus, under treatment I. Moreover, C. gariepinus yield in treatment II was 47.7% of that of treatment I, while yield in treatment III was 15.6% and 32.7% of those of treatments I and II respectively. Furthermore, the comparisons of the daily growth rate for each of the fish species under different treatments, were made. Statistical analysis showed that there is no difference (F7/0.10 and F7 0.05) in the mean growth rate and average yield of both fish species, in all the treatments. A further comparison of these parameters (mean daily growth rate and average yield) showed that there was significant difference in the mean daily growth rate between treatments I and III only, and in the mean yield between treatment I and II, I and !!! and II and III. Furthermore, the possible effect of some physicochemical parameters of the pond water, on the growth and survivability of the stocked fish species were discussed.Item Sex determination in Heterotis niloticus (Curvier 1829) based on morphometric features(UNAAB, 2007) Oladosu G.A.; Obi A.; Oladosu O. O.This study examined the morphometric and meristic characters of African Bony Tongue (Heterotis niloticus) in order to identify possible phenotypic sex markers in this potential aquaculture species. The ratios of extemal measurements of the dorsal length, the pre-dorsal length, the head length, the peduncle length, the anal length, the pectoral length, the pelvic length and the caudal length to the standard length was determined. The inter-orbital length of head length and the snout length of head length were also analyzed. The analyses were done in thirty (30) specimens of Heterotis niloticus. Only two of the morphological ratios namely peduncle length of the standard length and the inter- orbital length of the head length indicated significantly higher values (P<0.05) in the females. The ratio of peduncle length to the standard length in the female was 5.13 ± 0.56 and 4.89 ± 0.43 was re- corded in the male, while the ratio of inter-orbital length to head length in the female was 39.35 ± 2.16 and 37.54 +2.05 was recorded in the male. Sensory pits count on both the right and the left opercula plates were higher in the male than the female though, the difference was not significant enough for sensory pits count to form the basis for sexual dimorphism. The dimorphism so indicated in peduncle length and inter-orbital length is not readily observable by visual examination and may require simple measurements, which may not be easily carried out for routine sex determination on the field. However, it can be used to separate the broodstock population into different male and female holding facilities, while exteriorization of sexual products by catheterization or hand stripping can be used to confirm the sex of the selected broodstock and their readiness to spawn during the breeding season.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.