Judul: Distribusi dan Kelimpahan Larva Ikan di Perairan Laguna Pulau Pari dan Sekitarnya
Abstrak: Research on Fish larvae abundance and distribution has been conducted in Pulau Pari’s lagoon waters started from June to November 2011. The 5 sampling stations are Pulau Tikus (1), Pulau Burung (2), Pulau Kongsi (3), Tubir (4) dan LIPI (5). The result found there are 22844 fish larvaes consists of 67 families and 107 genera. The top 5 families with highest composition are Aulostomidae with 13.14%, followed by Blenniidae (9.98%), Pomacentridae (9.28%), Engraulidae (6.46%) and Pinguipedidae (5.02%). While the top 5 genera are Aulostomus chinensis of Aulostomidae (13.14%), followed by Stanulus of Blenniidae (5.95%), Stolephorus of Engraulidae (5.68%), Parapercis of Pinguipedidae (5.02%) and Pomacentrus of Pomacentridae (4.58%) The abundance range from 8 – 2764 ind/m3. Spatially, the highest abundance of fish larvae are in station 2 followed by station 4 while the lowest is in station 5. Temporally, the highest abundance of fish larvae are in July at station 1,3 and 4 while at station 2 and 5 the highest was in June. The highest abundance genus is Aulostomus chinensis. Most of families caught are reef associated fishes. Most of the genera also caught in preflexion stadia especially in July and October. Analyzes on community indices showed that the highest diversity index’s values is on station 4 with 3.03 and the lowest is station 5 with 2.8. correlation analyzes between environmental factors showed that negative correlation between abundance and temperature; also between abundance and nitrat while positive correlation showed by abundance and pH, abundance and salinity; and between abundance and silicate.
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Judul: Trofodinamik Fitoplankton-Zooplankton sebagai Penentu Kelangsungan Hidup Larva Ikan di Laguna Pulau Pari Kepulauan Seribu
Abstrak: Fish larvae utilize planktonic organisms as a food. Their Feeding success is determined by the dynamic of biomass and structure composition of phytoplankton and zooplankton population. The work is aimed to investigate the dynamic of biomass and composition of planktonic organisms and their relationship to the environmental conditions and also to determine the growth and development of fish larvae. The measurement of physical, chemical and biological parameters was conducted periodically at 5 stations. Grazing experiments were conducted to predict the growth and grazing rate of planktonic organisms such as nanophytoplankton, microphytoplankton, microzooplancton, mesozooplankton and fish larvae in many combinations of organism. Results show that environment condition of Pulau Pari lagoon was good and could support the survival of marine biota. Phytoplankton biomass was largely composed by size fraction of < 20 μm in the amount of 82,10 – 93,40 % from total chlorophyll-a concentration. Phytoplakton size fraction of ≥ 20 μm, was dominated by Bacillariophyceae genus Skeletonema and Chaetoceros. Zooplankton biomass was largely composed by size fraction < 200 μm (microzooplankton) in the amount of 63,90 % from total zooplankton biomass. Zooplankton was dominated by Class Crustacea, sub Class Copepod for microzooplankton and sub Class Malacostraca for mesozooplankton. Fish larvae were dominated by family Pomacentridae, Aulostomidae, Blenniidae, Engraulidae dan Pinguipedidae. The fish larvae in pre flexion stage development consisted of 62,985 from total larval abundance. The peaks of fish larvae biomass occurred in July and October, might indicate the larval production seasons. The dynamic of fish larvae biomass in July was in a “match” condition with that of other planktonic organisms, resulting a growth and development especially Blenniidae. While in October was in a “mismatch” condition this is probably due to food limitation. All of the planktonic organisms were influenced by the environment condition although there was no significant correlation among them. Grazing experiment shows that nanophytoplankton was the main prey of microzooplankton while microphytoplankton is the main prey of mesozooplankton. Fish larvae graze all components of planktonic organisms however the most abundance prey found in the stomach of fish larvae was microzooplankton. Allover of this study suggest that to support the ecological function of Pulau Pari lagoon as a spawning and nursery grounds, environment management would be needed to conserve natural habitat in the lagoon by rehabilitation of coral reef and seagrass ecosystems.
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Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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