Search

Tor tambroides is an important and highly valued freshwater fish. In Malaysia, wild populations of this species has undergone declines in range and abundance due to degradation of their natural habitat. Due to economic important and concerns about their conservation, a culture artificial propagation programme was established to produced seed-stock for aquaculture and conservation purposes. The effectiveness of selected synthetic and non-synthetic commercial hormones was tested on filial 1 generation (F1) of Tor tambroides (Bleeker 1854) females in captivity. A total of 144 matured females were given intramuscular implantation of slow release hormone, Ovaplant (38.6-53.6 μg kg-1 b.wt.), for 5-6 weeks prior to induction. Selected commercial hormones were compared for the induction. The effect of these hormones on breeding performance and larval quality of F1 Tor tambroides were evaluated. The results showed that Ovatide (0.5 mL kg-1 BW) was the most reliable hormone in inducing ovulation of F1 T. tambroides females overshadowed the other tested hormones. Ovaprim (0.5 mL kg-1 b.wt.) was the next best tested hormone followed by a synthetic analogue of salmon gonadotropin releasing hormone (sGnRHa/OvaRH) (10 μg kg-1 b.wt.). No ovulation occurred in the groups treated with Luteinizing Hormone Releasing Hormone Analogue (LHRHa) (10 μg kg-1 b.wt.), Human Chorionic Gonadotropin (HCG) (1000 μg kg-1 b.wt.) and Carp Pituitary Extract (CPE) (10 mg kg-1 b.wt.). Ovatide was further chosen to test its effectiveness at various dosage levels in inducing ovulation of T. tambroides. Thus, concentration of 0.5 mL kg-1 b.wt. of Ovatide was found to be the optimum dosage for inducing ovulation of F1 T. tambroides in captivity.

The present study was carried out to investigate the embryonic and larval development of the endangered Temoleh, Probarbus jullieni in lab-rearing condition. The matured egg and sperm were collected by stripping the bloodstock of Temoleh fish after injecting with ovaprim hormone extract. The samples were collected from hatching tank at every 10 min interval for the first hour, 20 min for the second hour, 30 min for the third hour and then hourly interval up to hatching. After hatching, larvae were observed daily until the complete disappearance of the yolk sacs. The fertilized eggs were spherical, demersal, adhesive and brownish-yellow in colour with a mean diameter of 2316 μm. First cleavage occurred within 10 min post-fertilization at temperature ranged from 26.0 to 28.0°C. Hatching started 22 h post-fertilization and completed within 25 h at the same temperature. The yolk sac was completely absorbed 61 h after hatching. At the same time, the larvae started to swim actively and feed exogenously. This marks the first description on the early life history of P. jullieni. The present study will provide some valuable information on the ontogeny, breeding biology and early larval rearing protocol of P. jullieni which will ultimately be helpful towards the establishment of large scale seed production technique for conservation and aquaculture production.

The presence of Asian catfish, Clarias batrachus in Malaysia is at a deteriorating state. It is hardly a cultured species since the supply of seed is unavailable. This species is found in lowland streams, swamp and rice fields. Therefore, they are greatly exposed to factors such as intermittent periods of drought, devastation of the natural habitat and agro-chemicals. Presently, fish farmers are more into the culture of Clarias gariepinus. This threatened the mere existence of this indigenous C. batrachus. Hardiness, good growth, efficient food conversion and excellent nutritional profile guarantee C. batrachus as a suitable aquaculture candidate. Some conservation efforts were looked into in order to prevent the extinction of this potentially important catfish.

Induced ovulation of captive Malaysian mahseer (Tor tambroides) often encounters low reproductive performances. The present study was conducted to gain insight to problems associated with poor breeding performance of Malaysian mahseer in captivity. In this study, sex steroid hormone levels and ovulation performance in filial 1 (F1) generation of Malaysian mahseer (Tor tambroides) were investigated. Fishes were injected with ovatide, combination of Salmon Gonadotropin Releasing Hormone Analogue (sGnRHa), DOM, sGnRHa+DOM and 0.9% NaCl. A total of 30 matured females T. tambroides with weight ranged from 2.01-3.80 kg were used in this study. The females were given ovaplant (39.5-37.3 μg kg-1) pretreatment for 6 weeks prior to hormones injection. Females were given a single intramuscular injection of ovatide (0.5 mL kg-1 b.wt.), sGnRHa (10 μg kg-1 b.wt.), DOM (5 mg kg-1 b.wt.), sGnRHa+DOM (10 μg kg-1 b.wt.+5 mg kg-1 b.wt.) or 0.9% NaCl. Blood samples were collected at 0, 6, 12 and 24 h (s) after injection. The effect of these treatments on sex steroids level (Testosterone (T) and 17β-Estradiol (E2) and ovulation performance of F1 Tor tambroides were evaluated. Result showed that higher ovulatory response was observed in the group treated with positive control ovatide (0.5 mL kg-1 b.wt.). Interestingly, it was observed that sGnRHa and Domperidone (DOM) produce highest egg and larval qualities compared to ovatide and sGnRHa alone. No ovulation occurred in the group treated with DOM alone. Sex steroids plasma concentration of T and E2 increased significantly in association with ovulation. The levels fluctuated and reached a peak at 12 h, then dropped dramatically at 24 Post Injection (PI). In contrast the non-ovulated groups, the sex steroids hormone concentration showed little increment after injection and rose at 12 h PI, then slowly dropped at 24 h pi. These results provide evidence for a strong dopamine inhibition on GtH secretion in captive mahseer.

The aim of this study was to characterize embryonic and larval developmental stages of the river catfish, Hemibagrus nemurus. Fertilized eggs were spherical, adhesive and demersal with a mean egg diameter of 1.5±0.3 mm. Seven embryonic periods were characterized for timing and features: zygote, cleavage, blastula, gastrula, segmentation, pharyngula and hatching. Mean hatch was 23±1 h post fertilization at 27°C. The newly hatched larvae measured 3.0±0.2 mm in total length. Morphogenesis was completed in a day. The yolk sac was completely absorbed in three days. H. nemurus has a short embryonic developmental period in comparison with other catfish species. The information obtained from this study will be useful for egg incubation and larval rearing during the culture of H. nemurus.