Judul: EFFECT OF SEDIMENTATION RATES AND CARNIVOROUS FISHES ON FOOD & HABITAT PREFERENCES OF CORALLIVOROUS FISH (CHAETODON OCTOFASCIATUS) IN THE SERIBU ISLANDS
Abstrak: Sedimentation rates are a major stress factor for coral reefs. It also impacts the feeding behavior and habitat of corallivorous fishes. The presence of carnivorous fishes may also influence the feeding behavior of corallivorous fishes. This study aimed to assess the relationship between Chaetodon octofasciatus and hard coral (HC) cover. In addition, sedimentation rates and predator abundance were assessed as potential influence. Data were collected at 4 different sites in the Seribu Islands north of Jakarta/Indonesia, including the abundance of Chaetodontidae and carnivorous fishes, Chaetodon octofasciatus behavior, coral reef cover, and sedimentation rates. The abundance of fishes was assessed using 50-m length belt transects deployed at 3-m depth. Coral reef cover was assessed using the Point Intercept Transect (PIT) method with 100 points for each transect. Data on fish behavior was recorded using the Focal Animal method to assess feeding rates and prey selectivity. 10 sediment traps were mounted at each site and collected after 30 days of deployment to obtain sediment samples, which were analyzed for sediment dry weight, ash-free dry weight, and organic content in the laboratory. The study results showed that the condition of coral reefs at Panjang, Belanda, and Pelangi is currently fair in terms of hard coral cover (HC<50%), while Kelapa had poor reef conditions (HC<25%). The abundance of C. octofasciatus had a high relationship with HC cover and showed a weak relationship with predators. Sedimentation rates had the strongest relationship with the feeding rates of C. octofasciatus compared with predators and HC cover.
Keyword: Chaetodon octofasciatus, Terumbu karang, Sedimentasi, Kepulauan Seribu, Laju pemangsaan, Ikan terumbu, Ikan predator, Ikan Kupu-kupu, Butterflyfish, Coral reef, Sedimentation, Reef fishes, Predator fishes, Feeding rates

Judul: Bioecological Study of Eightband butterflyfish (Chaetodon octofasciatus, Bloch 1787) to Detect Condition of Coral Reef Ecosystem in East Petondan Island, Seribu Islands, Jakarta
Abstrak: Monitoring the changes of coral reefs is an important task considering many of the world’s coral reefs have been destroyed or severely degraded. There are reliable ways to indirectly assess the changes of a coral reef and monitor it through time: certain members of an easily identifiable conspicuous family of fish, Chaetodontidae, have been considered to be reliable indicators of reef health. Data of Chaetodon octofasciatus are based on field observation using SCUBA set on the reef slope (3 and 10 meter) and food and feeding habit analysis conduct in the laboratory. The percent coverage of living corals was estimated on the reef slope (3 and 10 meter) at all sites. A 50 m line transect were laid at each site and depth. By using belt transect the abundance of C. octofasciatus and the occurrence of each coral genus were counted and recorded in data sheets. Feeding rates were calculated by observing randomly selected species at study area. Ivlev’s electivity index was used to measure feeding selectivity, comparing the utilization of food with respect to its availability. The feeding bites to be larger in rich reef corals with high percentage of live coral. The feeding rates in south, west and north site which have high percentage of live coral is highest comparing to east site which have low percentage of live coral. Based on food and feeding analysis, the fish stomach contain 94,1% coral nematocysts and 0,59% periphytic algae, which indicated C. octofasciatus as an obligate coralivores.
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Judul: The Exploration of Discrete Logarithm over Finite Field GF(3m)
Abstrak: The security of many public~key algorithms is based on the problem of finding discrete logarithms. The generalized discrete logarithm problem is the following: given a finite cyclic group G of order n, a generator a of G, and an element fl E G, find the integer x, 0 ~ x ~ n - 1, such that 0: = fl. Algorithm for discrete logarithm problem focused on Menezes et al. (1997) that consist of exhaustive search algorithm, the baby-step giant-step algorithm, Pollard's rho algorithm, Pohlig-Hellman algorithm, and index-calculus algorithm. These algorithms are explorated to be used in discrete logarithm problem over finite field GF(3m ). The exploration also produces some algorithms, i.e. naif negative algorithm, baby-step mother-step algorithm, baby-step mother free-step algorithm, and baby-step free-step algorithm. All algorithms implemented using Maple 11. The Pohlig-Hellman and baby-step giant-step algorithms are efficient enough to be used in discrete logarithm problem over finite field GF(3m ) for m < 20.
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