The size frequency distribution for age structure and length weight relationship of three species of the genus Acetes from the coastal waters of Malacca, Peninsular Malaysia are reported. The length frequency distribution for A. indicus suggested that the population consisted of two dominant age groups with mean at 20.80 (± 2.42) mm and 29.85 (± 2.79) mm of total length, respectively. The population of A. japonicus consisted of maximum two age groups, with means of 15.18 (± 0.90) mm and 21.56 (± 1.03) mm of total length. The population of A. intermedius also consisted of maximum two age groups, with means of 19.18 (± 2.45) mm and 26.92 (± 2.82) mm of total length. The positive allometric nature of growth for A. indicus was observed in the coastal waters of Malacca. But isometric nature of growth was found in combined sexes of A. japonicus. The positive allometric nature of growth was observed in female and both sexes of A. intermedius. There were significant difference between males and females size-frequency distribution of A. indicus (Kolmogorov-Smirnov test: dmax= 0.42, P < 0.001), A. japonicus (Kolmogorov-Smirnov test: dmax = 0.39, P < 0.001) and A. intermedius (Kolmogorov-Smirnov test: dmax = 0.40, P < 0.001). The significant differences were observed between mean total length of female and male of A. indicus, A. japonicus and A. intermedius (t-test, P < 0.001).
The effect of gonadotropin releasing hormone analogue (GnRHa) on plasma sex steroid hormones of river catfish Hemibagrus nemurus was studied. Enzyme linked immunosorbent assay (ELISA) was used to measure the hormones. The fish were treated with saline (control) and GnRHa at various doses of 5 μg/kg, 20 μg/kg and 50 μg/kg body weight (BW) of fish. Blood samples were collected at 0, 6, 12 and 24 h post hormone administration. The results showed that GnRHa elevated the plasma sex steroid hormones even at a low dose of 5 μg/kg. Significant increase (p< 0.05) in plasma sex steroid levels were observed with 20 μg/kg and 50 μg/kg BW GnRHa treatments and a dose of 5 μg/kg BW GnRHa produced a slow response to steroidogenesis. Treatment with 50 μg/kg BW GnRHa produced the best result. The highest level of testosterone, 11-ketotestosterone and 17β-estradiol were observed at 24 h for all treatments. The results indicated that GnRHa increased steroid production in the plasma of H. nemurus. Therefore, it can be used as an inducing agent for the control of reproduction in H. nemurus.
This study examined the genetic characteristics of twenty-six microsatellite primers developed from three cyprinid fishes (Cyprinus carpio Linnaeus, Barbus barbus Linnaeus and Barbonymus gonionotus Bleeker) in two indigenous mahseer. The Tor douronensis Valenciennes were randomly collected from two locations in Sarawak (N=52), while Tor tambroides Bleeker were obtained from Peninsular Malaysia (N=56). A total of ten and twelve primers were successfully amplified producing four and five polymorphic loci in T. douronensis and T. tambroides, respectively. The number of alleles per locus ranging from 2 to 5 in T. douronensis and 2 to 7 in T. tambroides. A significant deviation from Hardy-Weinberg equilibrium (HWE) was observed at three loci (Barb37, Barb59 and Barb62) in one or more populations in T. tambroides while two loci (Barb37 and Barb62) were deviated in T. douronensis population of Batang Ai. Population structure analysis showed low level of inter-population genetic differentiation in both mahseer. Overall, the identified microsatellite loci should be useful in analysing T. douronensis and T. tambroides natural populations.