Browsing by Author "Oladosu G.A."

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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.
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. G
A 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.
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.