Judul: Diel Variation of Fish Community  Associated with Seagrass Beds in Panggang Island, Kepulauan Seribu National  Park
Abstrak: Lamun merupakan salah satu ekosistem utama yang memiliki peran penting di wilayah pesisir yang berfungsi sebagai habitat dan daerah asuhan ikan. Penelitian ini bertujuan untuk mengungkap variasi komunitas ikan yang berasosiasi dengan padang lamun di Pulau Panggang bagian timur pada waktu siang dan malam hari. Pengambilan ikan dilakukan selama bulan Februari hingga Agustus 2018 menggunakan pukat tarik (seine net). Sampel ikan diidentifikasi dan diukur panjang serta bobotnya di laboratorium. Ikan yang terkumpul selama penelitian sebanyak 9.026 ekor yang terdiri atas 82 spesies, 63 genera, 35 famili, dan 15 ordo. Atherinomorus duodecimalis, Cheilodipterus quinquelineatus, dan Gerres oyena ditemukan dengan kelimpahan besar selama penelitian pada waktu siang dan malam. A. duodecimalis dan G. oyena banyak ditemukan dalam stadia yuwana. Terdapat perbedaan struktur komunitas ikan pada siang dan malam hari. Biomassa ikan pada siang hari didominasi oleh famili Labridae (24%), sedangkan biomassa ikan malam hari didominasi oleh famili Apogonidae (31%). Perubahan biomassa ikan menunjukkan adanya migrasi harian ikan untuk mencari makan. Komposisi ikan pada waktu siang dan malam didominasi oleh yuwana sebesar 73% dan 65%. Temuan ini menunjukkan bahwa padang lamun di Pulau Panggang berperan sebagai daerah asuhan yuwana ikan dan tempat mencari makan bagi ikan-ikan dewasa., Seagrass is one of the main ecosystems which has an important role in the coastal area as a habitat and nursery area for fishes. This study aimed to compare the fish communities associated with seagrass beds in the eastern part of Panggang Island during the day and night time. The fish collection was carried out from February to August 2018 using a seine net. Fish samples were identified and their body length and body weight were measured in the laboratory. A total of 9,026 individuals were collected, consisting of 82 species, 63 genera, 35 families, and 15 orders. Atherinomorus duodecimalis, Cheilodipterus quinquelineatus, and Gerres oyena were found in great abundance during the day and night time. A. duodecimalis and G. oyena mostly found in the juveniles stage. There was a significant difference in the structure of the fish community between day and night. Labridae was the most abundant in biomass in the day (24%), while Apogonidae was the most abundant at night (31%). Changes in fish biomass indicate that daily fish migration for feeding is occurring. During the day and night time, the composition of fish was dominated by juveniles with 73% and 65% of total catches, respectively. These findings indicate that seagrass beds in Panggang Island play an important role as nursery ground for fish juveniles and feeding ground for adult fishes.
Keyword: daerah asuhan, daerah mencari makan, komunitas ikan, lamun, variasi harian

Judul: Food and Trophic Guild of Fish Assemblages in the  Seagrass Ecosystem of Panggang Island, Kepulauan Seribu
Abstrak: Pulau Panggang dengan jumlah penduduk terbanyak di Taman Nasional Kepulauan Seribu memiliki ekosistem lamun. Ekosistem lamun berperan penting bagi kehidupan ikan yaitu sebagai daerah asuhan dan tempat mencari makan kumpulan ikan. Penelitian ini bertujuan untuk menentukan peran fungsional komunitas ikan yang berasosiasi dengan padang lamun secara temporal (siang dan malam) di perairan Pulau Panggang, Kepulauan Seribu. Pengambilan sampel ikan dengan pukat tarik dilakukan pada siang dan malam hari selama lima bulan yaitu April, Mei, Juli, Agustus, dan September 2018. Analisis data yang digunakan meliputi indeks bagian terbesar, tingkat trofik, dan strategi pola makan ikan. Sebanyak 74 spesies ikan dari 55 genera dan 30 famili ditemukan selama penelitian. Sebagian besar ikan yang tertangkap berada pada stadia yuwana dengan status kepenghunian pengunjung sesekali. Makanan dominan yang dikonsumsi ikan yang berasosiasi dengan padang lamun pada siang dan malam hari berturut-turut adalah krustasea dan zooplankton. Peran fungsional kumpulan ikan di padang lamun Pulau Panggang pada siang dan malam hari terdiri atas tujuh serikat trofik yaitu detritivora, fitoplanktivora, algivora, zooplanktivora, zoobentivora, krustasivora, dan piscivora dengan nilai tingkat trofik berkisar antara 2,00 sampai dengan 4,50. Secara keseluruhan, ikan yang berasosiasi dengan lamun melakukan strategi pola makan generalis-spesialis. Studi ini menegaskan bahwa sebagian besar spesies ikan laut menggunakan padang lamun di perairan Pulau Panggang sebagai daerah asuhan dan mencari makan., Panggang Island with the largest population in the Kepulauan Seribu Nasional Park has a seagrass ecosystem. Seagrass ecosystem plays an important role as a nursery and feeding grounds for fish assemblages. The purpose of the study was to determine the functional part of the seagrass-associated fish community temporally (day and night) in the waters of Panggang Island, Kepulauan Seribu. Fish sampling with seine net was conducted day and night for five months, namely April, May, July, August, and September 2018. Data analysis includes an index of preponderance, trophic level, and fish diet strategy. A total of 74 fish species from 55 genera and 30 families was collected. Most of them were fish juveniles with the residential status as occasional visitors. The dominant food items consumed by seagrass-associated fish during day and night were crustaceans and zooplankton, respectively. The functional role of fish assemblages during the day and night consists of seven trophic guilds: detritivores, phytoplanktivores, algivores, zooplanktivores zoobentivores, crustacivores, and piscivores with trophic level values ranging from 2.00 to 4.50. Overall, seagrass-associated fish performed a generalist-specialist feeding strategy. This study confirms that most marine fish species use the seagrass beds on Panggang Island as nurseries and feeding grounds.
Keyword: fish assemblages, juvenile, Panggang Island, seagrass bed, trophic guild

Judul: Real Option Valuation Using Binomial Decision Trees.
Abstrak: A firm that decides to invest has a choice to invest in real assets. A method which is usually used in valuation of the project is discounted cash flow (DCF) method. But, this method can’t be used in projects that account for value of managerial flexibility, such as decision to suspend operations temporarily. Therefore, this kind of project needs to be assessed using real option. Real option valuation can be done in some ways, including the use of path-dependent simulation, as well as closed-form models like Black-Scholes model, partial differential equation, and binomial or multinomial approaches. In this paper, real option valuation using binomial decisions id discussed. Determination of the project value can be done in three steps. First, calculate the expected present value of the project. Next, calculate volatility of the project using Monte Carlo simulation. Last, construct a binomial tree to model the dynamics of the project value using the parameters of the stochastic process, and then add some decision nodes to model the project’s real options.
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