Judul: Ecobiology of “Sepetang” (Pharella acutidensBroderip & Sowerby, 1828) clamin mangrove ecosystem Dumai Coastal Riau
Abstrak: The“Sepetang” (P. acutidens) clam population in Dumai mangrove ecosystem seemed to decrease due to the increase of mangrove degradation and clam exploitation. The aims of the study were todetermine the population and reproductive biology character of the“sepetang” (P. acutidens)clam and their relationship with biophysical and chemical characteristic of mangrove ecosystem.The study was carried out from November 2010 to October 2011 inDumai mangrove ecosystem. Population biology aspects such as patterns of the population growth, mortality and recruitment of the clam P. acutidens were determined.Reproductive biology aspects such as sex ratio, gonadal development,gonadosomatic index, fecundity and oocytes diameter were also studied.The “sepetang” clam habitat characteristic was evaluated based on biophysical and chemical parameters of mangrove environment at each station using principal component analysis. Descriptive analysis was used to evaluate relationship between “sepetang” biological character and mangrove ecosystem environment characteristics. Correspondence analysis was used to analyze spatial distribution of “sepetang” clam in relation with biological character. The results showed that the study area was classified into four groups of stations. First, consists of station SM1 and SM2 was characterized by high concentration of nitrate and phosphate, organic sediment, silt fraction, X. granatum andR. apiculata mangrove species density. Seconds, consists of station P1, P2 and P3 characterized by high salinity, sand and clay fraction, and H. littoralis mangrove species density. Third, consist of station SM3 characterized by high pH of water and sediment and plankton density. Fourth, consists of stasion SD1, SD2 and SD3 characterized by high density of B. gymnorrhiza and A. alba. The growth pattern of P. acutidens was negative allometric with asymptotic length (L ) was 92.71 mm. The annual growth coefficient (K) and total mortality were 0.59 and 1.87 per year, respectively. The recruitment occurred every month.Sex of the sepetang clam can be determined at the size more than 35 mm. The male to female ratio was 1 : 1.12 and no specimen hermaphroditism was observed. Histological analysis indicated that P. acutidenswas partially spawned. The fecundity increase with an increase of shell length and correlated significantly with shell length. The sepetang clam probably spawn continuously throughout the year with a peak spawning season between May-June. The results showed that high gonadosomatic index and fecundity of “sepetang” clam in station SM1, SM2 and SM3. The stations were characteristized by high organic sediment, silt fraction, andR. apiculata density.
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Judul: Bioecological of Mud Crabs (Scyllaspp.) in mangrove ekosistem of Subang Regency, West Java
Abstrak: The aim of the research was to collect data and information concerning population structure, reproduction performance, reproduction potency, evaluation of eyestalk ablation and distribution of mud crabs based on the characteristics of their environment habitat. The research was carried out since January 2005 to August 2006. Observation on the morphology and anatomy used descriptive method. The ecological aspect was done in situ using line plot transect method. In the meantime, the aspect of biological reproduction was carried out through a controlled seed experiment in pond and laboratory with treatment of eyestalk ablation. Exploration of eyestalk tissue of mud crabs was performed with the method of histochemistry to assure the success of ablation. The result showed that not only the morphology of different mud crab species but also the morphology and anatomy of crabs with different sexes. The mud crabs from different research stations indicated differences in terms of the population rate. The width of the carapace and minimum and maximum weight of mud crabs caught were different from one species to another.
Keyword: pupulation structure, reproduction performance, reproduction potency, distribution of mud crabs, West Java

Judul: Construction of Strongly Optimal Binary Linear Code with Minimum Distance 9 and 11
Abstrak: A binary linear code of length n over q F is a subspace of n q F . A code has three parameters that attached to it, namely length, dimension, and minimum distance. A code with length n, dimension k and minimum distance d is often called [n, k, d ]-code. Usually, when two parameters are given, then we want to find a code that has the best value for the last parameter. Based on Gilbert- Varshamov bound, if a [n, k, d ]-code exists and can not be expanded, we call it a strongly optimal code. In this paper, we construct strongly optimal code with minimum distance 9 and 11. In constructing the code, we created a theorem and algorithm based on Gilbert-Varshamov bound before we implement the algorithm to MAPLE programming language. Because of computational limitations, the program can only construct up to k = 10 for d = 9 and k = 12 for d = 11.
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