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 study was conducted at Merambong Shoal (01°19.979’N, 103°35.965’E) in the Sungai Pulai estuary, Johor Straits, Malaysia from January to December 2005. Standing biomass of male and female Strombus canarium sub populations was calculated monthly based on the abundance value of each cohort and on the length-weight relationship. Secondary production was estimated using increment summation method, upon recognition of cohorts following the size-frequency distribution analysis using Bhattacharya and Hasselblad’s NORMSEP methods. Monthly variations in standing biomass
(B) and production (P) showed higher values during the wet season compared to dry season, which indicate seasonal variations. Total production (P) was estimated at 0.14 gAFDWm-2yr-1 and 0.45 gAFDWm-2yr-1, while the annual mean population biomass was estimated at 0.13 gAFDWm-2 and 0.26 gAFDWm-2, for males and females, respectively. The P/ ratio was therefore calculated at 1.08 yr-1 for male and 1.73 yr-1 for female, which was within the values reported for other gastropod species. Estimates using empirical methods commonly used in secondary production studies found
that none could be applied to the species. Considering the large amount of time, effort and resources involved in the conventional production estimation method, more studies are needed to establish a reliable production estimates for S. canarium, and possibly other gastropod species within the tropical region.
A total of 230 individuals of Strombus were sampled at various locations along the Johor Straits, Malaysia. There were four species of Strombus present in the study areas i.e. Strombus canarium Linnaeus, 1758; Strombus urceus Linnaeus, 1758; Strombus marginatus subspecies succinctus Linnaeus, 1767; Strombus marginatus subspecies robustus Sowerby, 1874; and Strombus vittatus subspecies vittatus Linnaeus, 1758. Strombus canarium was the most common, widely distributed and most abundant, followed by S. urceus, while the others were only rarely found. Among the species Strombus marginatus and Strombus vittatus were two new distribution records for the Johor Straits. Since all Strombus were traditionally harvested and consumed by the locals since long ago, further studies are needed particularly regarding the population dynamics and fishery of the harvested species.
Samples of Pinna bicolor Gmelin and Pinna deltodes Menke were collected from the seagrass bed of Sungai Pulai, covering Merambong shoal, Tanjung Adang shoal and Merambong Island off south western coast of Johor, Malaysia for morphological study from August 2005 to June 2006. It was observed that P. deltodes is associated with hard substratum and P. bicolor is associated with soft substratum in the study area. Physically there was no difference between P. bicolor and P. deltodes. The species were identified on the basis of nine internal and external characteristics of the valves. The two species were found to be morphologically different on the basis of width of sulcus, distance between posterior adductor muscle to posterior dorsal nacreous layer, dorsal posterior margin length and shell width.
The abundance of marine benthic organisms often exhibits distinct distributional patterns, which is generally governed by many physical and biological factors specific to the habitat. In this study, the spatial and temporal variations in abundance of the dog conch, Strombus canarium Linnaeus 1758, a commercially important marine gastropod, was investigated. Assessment of conch abundance at Merambong seagrass bed, Malaysia, was conducted using a transect belt method. Sampling stations were randomly selected and environmental parameters associated with the habitat were recorded. The species showed distinct spatial distributional pattern. Conch densities were significantly higher in sheltered areas, mainly in mixed seagrass bed dominated by Halophila spp. and with high sediment organic content. The densities were relatively very low in areas dominated by the tape seagrass, Enhalus acoroides. The species studied also showed distinct temporal variation in abundance. The abundance value was seasonally varied with highest density recorded during the wet monsoon season (p<0.05). The densities were otherwise very low during the dry season, except for a slight peak in July. Since the conch is a very important fishery species within the Johor Straits and regulations on their harvesting is still lacking, this information would be very important for their sustainable management.