الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 282 |  |  |
| | | from | 282 | | |
Abstract
This study has been carried out on various phases of induced spawning of Clarias gariepinus broodspawners, fertilization of eggs, egg incubation, hatching and early rearing of the larvae for schedulling and standardizing the process of fingerlings large scale mass production. The number of females used in this study was 135. They were pretreated under the same environmental and pond mangement conditions in order to minimize the individual variation. They were categorized into three different size groups A, B and C (45 individuals each), with average individual body weight of 311.6 ± 10.3, 460.5 ± 11.8 and 611.2 ± 8 grams, respectively. Each size group was sorted randomly into nine simillar subgroups (5 femals each ). Females of the subgroups Ai.3, B1_3 and C 1.3 were injected with HCG. Individuals of the subgroups A4-6, B4-6 and C4-6 were iniected with CLPs. However fish of the subgroups A7_9, B7.9 and C7_9 were injected with CPs. Individuals of the subgroups 1, 4 and 7 from each siz group were then kept separately in aquaria filled with water at a temperature level of 22 °C . However, fish of the subroups 2, 5 and 8 of the three siz groups were placed separately in aquaria at water temerature of 25 °C. The water temperature for the 3rd, 6th and 9th subgroups of the same size groups were maintained at 30 °C. The potency of the three types of spawning inducing agents HC9, CLPs and CPs at the three different temperature levels 22, 25 and 30 °C were assessed among individuals of the three different size groups. The dose’s of the ovulation inducers were 4000 IU, 4mg and 4mg/ kg for HCG, CLPs and CPs, respectively given in two successive times (1/10, 9/10) with 8 hrs. time interval. The time of the first injectien was fixed on 4 p m The interaction effect of the three factors; type of inducer, temperature level and size of the female spawner, on the latency time, quantity and quality of eggs produced was evaluated. The results were as follows :- Ovulation was successfully induced in mature C. gariepinus females with the three ovulation inducers used nevertheles, hypophysation was more successfull when CLPs was used rather than HCG and CPs. this may be attributed to the direct gonadotropic action of the homoplastic pituitaries on oocyte maturation. Therefore, the present result suggests that in Clarias culture, CLPs could better be used specially since the males are sacrificed to obtain milt and fresh pituitaries could be collected from them. The optimal latency time at which the highest percentage of viable eggs could be stripped was 18-19, 16.45-18.0 and 15.0 - 16.30 (hrs. min.) at 22, 25 and 30 °C respectively, using HCG. When CLPs was used, the optimal latency time was approximately 15.0 to 16.30, 14.0 to 16.30 and 13.10 to 15.20 (hrs. min.) at the same temperatures, respectively. While by using CPs stripping was carried out following an optimal latent period of 16.20 to 17.40 (hrs. min.) at 22 °C, 16.0 to 17.0 (hrs. min.) at 25 °C and 14.30 to 15.45 (hrs. min.) at 30 °C. The optimal latency time appeared to be influenced by both temperature (inverse relation) and the type of injected agent, the latency time was shorter and the percentage of viable aggs was higher in case of injection with CLPs than that with HCG or CPs . A specified ovulation stimulating agent has a specified optimal latency time interval at different temperatures within which the treated females could be stripped . The egg production results showed a highly significant interaction effect of temperature, type of injection and female body weight on the total weight of stripped egges. ( r2 = 0.71 p <0.001). Duncan’s grouping of the individual treatment difference between the mean egg production at the three temperature levels. Also the mean of the total egg weight at the three injection levels did not differ significantly. However, there was significant difference among treatment when females of different size group were used. According to the analysis, the highest value of egg weight was produced when females of the largest size (size grop C) was injected with CLPs at water temperature of 30 °C. While the lowest value of egg production was deposited by females of the smallest siz ( size gropup A) when HCG was administered at 25 °C.