Judul: Asosiasi ikan dengan padang lamun di perairan karang lebar, kepulauan seribu, Jakarta
Abstrak: Seagrass is a complex aquatic ecosystem in trophics area with high productivity and biodiversity. This ecosystem play role of physics, chemistry, and biology. Biologically, seagrass used as spawning, feeding, and nursery ground for aquatic biota, especially fish. Seagrass is part of the coastal region where there are many human activities, such as coastal development, overfishing, boat traffic, and sand mining. One of the seagrass areas with high human activity around is Karang Lebar shallow waters, Kepulauan Seribu, Jakarta. Types of data taken in this research is primary data, including environmental parameters, condition of seagrass and fishes that live in it. Fishes caught by gill net with mesh size from 0.5 – 3 cm. Sampling conducted in day and night, started from March until May 2011 with the arrest period twice a month. Observations were made at three stations of seagrass beds with different covering conditions (healthy, less healthy, and poor). Sorensen similarity index, constancy index, and fidelity index were used to determine the relationship of fish associated with seagrasses. In addition, it also used statistical tests such as Pearson correlation, biplot analysis, and Two Way ANOVA as a tool to test the truth of descriptive analysis results based on the facts as represented by data. Three seagrass species found in the observation area include Thalassia hemprichii, Cymodocea rotundata, and Halophila ovalis. The highest cover obtained from Cymodocea rotundata. Value of total cover ranged between 26.5 % - 82.13 %. The highest INP of the species obtained from Cymodocea rotundata, indicate that these organisms have a great influence to the ecosystem. Fish were caught consist of 37 species and 22 genera. Total abundance was found in all three observation stations for 2287 individuals (healthy seagrass), 547 individuals (less healthy seagrass), and 889 individuals (poor seagrass). Pre-adult fish dominate at each station. While the most commonly species found are Hypoatherina temmincki, Gerres oyena, and Scolopsis lineatus. The catch composition on day and night differ in terms of abundance, type and size of the species. Adult fish were more common at night, although abundance in day were more than in the night. Based on size and species composition, healthy seagrass and less healthy seagrass functioning as nursery ground and feeding ground, while poor seagrass tend to play a role as feeding ground, especially for carnivorous fish. Change of the diversity and dominance value in the day and night allegedly due to the activity or movement of fish, which is not a permanent resident in seagrass. Referring Tomascik et al. (1997), permanent resident fish found in the observation area is Apogon margaritiphorus. Based on Sorensen similarity index, the fishes were divided into six groups of species. Constancy index ranging from 0-1, while fidelity index ranges from 0-3. Group of species 1 has a high preference on healthy and poor seagrasses, and low preference in unhealthy seagrasses. Healthy seagrass also preferred by group 6, which include Apogon kallopterus, Apogon margaritiphorus, Hemirhapus far, Chrysiptera hemicyanea, and Syngnathoides biaculeatus. Groups of species that have a high preference towards less healthy habitat is group 4, with Stethojulis balteata, and Chaetodon
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Judul: Sumberdaya Ikan Karang pada Berbagai Kondisi Kerapatan Lamun di Perairan Pulau Pasi Kabupaten Kepulauan Selayar Provinsi Sulawesi Selatan
Abstrak: Seagrasses are marine angiosperms, distributed in both tropical and temperate coastal waters creating one of the most productive aquatic ecosystems on earth. Due to the high primary production and a complex habitat structure, meadows formed by seagrasses support a variety of benthic, demersal and pelagic organisms. Many fish species are attracted to seagrass habitats for foraging and shelter, especially during their juvenile life stages. Thus, seagrass meadows are valuable resources for fisheries at both local and regional scales. The study presented the community structure, size distribution, species composition and spatial distribution of reef fish in seagrass habitats at Pasi Island waters. Sampling of fish was conducted in daylight and night using a small trawl. The total abundance and biomass of the reef fish in this research was 431 individual (13129 gram). Out of 55 different reef fish species from 24 families were recorded during the study, only one species accounted for more than 25% of the total abundance and biomass is Siganus canaliculatus. The study showed that the diversity and dominant indices of fish were generally significantly higher at station V with sand and reef fraction substrate dominated by Thalassodendron ciliatum and Cymodocea serrulata. Seagrass species with high density and percent cover value as Syringodium isoetifolium, Cymodocea serrulata and Thalassodendron ciliatum has a high fish diversity value. Seagrass species that has large and long leaves such as Thalassia hemprichii and Enhalus acoroides favored by reef fish planteater (herbivore) i.e. Siganus canaliculatus (Siganidae), Apogon melas (Apogonidae) and Scarus forsteni (Scaridae).
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Judul: Konstruksi aritmetika kurva eliptik F(2m) supersingular dan non-supersingular untuk skema kunci publik ElGamal
Abstrak: Algoritme ElGamal adalah salah satu algoritme kunci publik dengan aritmetik modular p yang mempunyai struktur grip siklik Z(p). Tingkat keanaman algoritme ini terletak pada pemecahan masalah logaritme diskret dari Z(p). Akan tetapi, tingkat keamanan tadi tahun ke tahun semakin menurun yang disebabkan kemampuan pemecahan algoritme diskret semakin meningkat. Untuk memenuhi tingkat keamanan yang memadai dibutuhkan p yang cukup besar yang menyebabkan proses enkripsi dan dekripsi menjadi lambat.
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