Judul: Pendugaan Kelimpahan Ikan di Perairan Utara Jawa Tengah dengan Metode Akustik dan Swept Area: Sebuah Pendekatan Geostatistika
Abstrak: This research was intended to apply geostatistical approach on fish abundance estimation in the north of Central Java waters. Analysis of trawl and acoustic data structure was performed using geostatistical analysis, estimation results of the experimental semi-variogram were then used to infer the characteristics of fish abundance in the north of Java waters. Swept area data obtained using bottom trawl while acoustic data obtained using SIMRAD EK60 with operating frequency at 120 KHz. Data processing includes the standardization of catch, integration of acoustic data extraction, transformation of geographic position in to UTM (Universal Transverse Mercator) format, variogram fitting model, abundance estimation using the model, and fish distribution mapping by kriging. Results of structural analysis and models fitting using geostatistical analysis showed that the most suitable model with all data used were spherical model (spherical) with different parameters and R2 values from different models, models with the highest R2 value 0.940 was obtained from 2005 acoustic data, while the model with lowest R2 value 0.559 was obtained on 2006 swept area data set. The models were then used to estimate the value of fish abundance and to obtain information on the points with no abundance of information through kriging process. Validity of a model in estimating and interpolation can be known through calculation of R2 values from crossvalidation process between the estimated value with the actual value, the higher the value of R2 from cross-validation process the better the model is doing prediction. From the calculations of cross-validation, R2 values obtained varied for each data set. The highest cross-validation R2 values obtained from 2005 acoustic data set that is equal to 0.911, while the lowest R2 value 0.316 was found in 2006 swept area data set. Differences in the estimated level of validity from each set data can be used in consideration in the implementation of data collection on fisheries surveys, especially to get a better result. Next step of the geostatistical application is estimating and mapping of fishery resources based on a model that has been obtained, so it can provide a snapshot of fish abundance and distribution condition in the north of Java waters. From geostatistical analysis abundance estimation results in this study can be seen that the abundance of pelagic fish resources in 2005 has a higher value compared with the year 2006, this indicates a decline in the abundance of pelagic fish resources, while from the prediction of the abundance of demersal fish resources showed a higher abundance for year 2006. Abundance difference between the prediction made in 2005 and 2006 can also due to seasonal differences caused by different time-survey. Fish distribution patterns obtained from the mapping can be used as information about the specific fish behavior to environmental conditions. Estimation of abundance using geostatistical analysis can provide estimates of abundance of fish resources with smaller coefficient of variation and standard deviation than ordinary arithmetic calculations. This indicates the abundance estimation using geostatistical analysis that use the spatial structure into account in the analysis is a better estimator than the ordinary arithmetic calculation (non-geospatial). To improve the accuracy
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Judul: Pendugaan kelimpahan dan distribusi ikan-ikan pelagis kecil dengan sistem Akustik Beam Ganda di Perairan pantai Jepara, Jawa Tengah
Abstrak: Penelitian ini adalah untuk menduga kelimpahan sediaan pelagis kecil di perairan Utara Jepara dan menduga distribusi vertikal dan horisontal ikan. Setelah melakukan berbagai kegiatan mulai dari persiapan, pengambilan data lapang sampai dengan pemrosesan hasil serta pelaporan didapatkan banyak hasil. Nilai in situ Target Strength (TS) ikan menyebar normal dari -54 dB sampai 32 dB dengan nilai rata-rata -47.62 dB. Setelah dikonversi dengan rumus Foote (1987): TS 20 log (L) 68 - diperoleh panjang ikan L = 10.44 cm. Dari data hasil tangkapan mid water trawl didapat nilai rata-rata panjang ikan 16 cm dan didominasi ikan Selar (famili Carangidae). Selisih panjang ikan ini dapat disebabkan data verifikasi yang diperoleh dari mid water trawl kurang mewakili keberadaan ikan-ikan pelagis secara keseluruhan di lokasi penelitian. Sampling verifikasi di perairan Utara Jepara hanya dilakukan satu kali yaitu pada posisi 05° 49' 53" LS dan 110° 56' 72" BT, sehingga data yang diperoleh masih lemah dan belum dapat membuktikan kebenaran metode akustik.
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Judul: Prenilasi Senyawa β-Diketon sebagai Prekursor 3-Prenilflavon
Abstrak: One group of flavonoids that has not been commonly synthesized is 3- prenylflavone. The main objective of this experiment was to synthesize precursor of 3-prenylflavone. Firstly, β-diketone was synthesized via 4 steps from phenol as starting compound with total yield of 24%. Prenylation of β-diketone with prenyl bromide and K2CO3 base produced 4 fractions which were separated by using preparative thin layer chromatography (PTLC) with n-hexane:EtOAc (8:2) as the eluent. Fraction with Rf = 0.80 was further separated by using preparative PTLC with n-hexane:EtOAc (99:1) as the eluent. Two fractions were obtained with Rf = 0.38 and 0.42. The first fraction has been characterized as diprenylated β-diketone with 49% yield. Application of protecting group on the phenolic OH group in β- diketone are needed to obtain monoprenylated β-diketone which can be further cyclized into 3-prenylflavone
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