Judul: Status Stock of Moonfish, Mene maculata (Bloch & Schneider, 1801), Based on Spawning Potential Ratio in Palabuhanratu Bay
Abstrak: Ikan semar (Mene maculata) merupakan salah satu tangkapan utama nelayan di Teluk Palabuhanratu dan memiliki nilai ekonomis yang tinggi. Penelitian ini bertujuan untuk menentukan status stok ikan semar di Teluk Palabuhanratu sebagai dasar pengelolaan perikanan yang berkelanjutan. Pengambilan data dilakukan pada bulan September 2021 hingga Februari 2022 dengan ukuran contoh ikan sebanyak 522 ekor. Jumlah ikan semar jantan lebih dominan dibandingkan ikan semar betina. Analisis pertumbuhan dengan metode ELEFAN menghasilkan panjang asimtotik (L∞) dan koefisien pertumbuhan (K) ikan semar jantan memiliki perbedaan dengan ikan semar betina. Analisis mortalitas menduga laju eksploitasi ikan jantan sebesar 0,73 dan betina sebesar 0,62 yang berarti ikan semar mengalami eksploitasi lebih. Analisis rasio potensi pemijahan berdasarkan ukuran panjang (LB-SPR) menunjukkan ikan semar jantan dan betina memiliki nilai SPR di bawah 40% sehingga diduga mengalami tangkap lebih rekrutmen., Moonfish (Mene maculata) is one of the main catches of fishermen in Palabuhanratu Bay and has important economic value. This research aims to determine the status of the moonfish stock in Palabuhanratu Bay as a basis for sustainable fisheries management. Data collected from September 2021 to February 2022 with a sample size of 522 fish. The number of male moonfish exceeded that of females. Growth analysis using the ELEFAN method resulted in different asymptotic length (L∞) and growth coefficient (K) values for male and female moonfish. Mortality analysis estimated that the exploitation rate for male moonfish is 0,73 and female moonfish is 0,62, which means they may be experiencing overfished. The analysis of length based - spawning potential ratio (LB-SPR) indicates that both male and female moonfish have SPR values below 40%, suggesting that they may be experiencing recruitment overfishing.
Keyword: exploitation rate, moonfish, Palabuhanratu Bay, stock status, sustainable fisheries

Judul: Reproductive Biology of Moonfish (Mene maculalata Bloch & Schneider, 1801) in Palabuhanratu during West Monsoon
Abstrak: Ikan semar (Mene maculata) merupakan ikan demersal dengan nilai ekologis dan ekonomis yang penting. Tingginya pemanfaatan ikan semar sebagai ikan konsumsi berpotensi mengganggu pola reproduksi, rekrutmen dan ketersediaan stok sumberdaya ikan semar, yang mana informasi biologi reproduksi minim pada musim barat. Oleh karena itu, penelitian ini bertujuan untuk menganalisis biologi reproduksi ikan semar di Teluk Palabuhanratu. Periode penelitian berlangsung pada bulan September 2021 hingga Februari 2022 (mewakili musim barat), dengan ikan contoh sebanyak 522 ekor. Pengambilan ikan contoh menggunakan metode penarikan contoh acak sederhana. Hasil menunjukkan bahwa nisbah kelamin sebesar 1:0,76 yang didominasi oleh ikan jantan. Ikan semar memiliki pola pertumbuhan allometrik negatif. Puncak musim pemijahan selama periode penelitian berada di bulan September dan Oktober. Potensi reproduksi berkisar 11.988 hingga 21.164 butir telur. Pola pemijahan ikan semar terindikasi total spawner yaitu pemijahan yang terjadi secara sekaligus. Hasil analisis menggunakan metode Spearman-Karber menunjukkan bahwa ukuran pertama kali ikan semar betina matang gonad (Lm) lebih dahulu dibanding ikan semar jantan., Moonfish (Mene maculata) is a demersal fish with important ecological and economic values. The high utilization of semar fish as consumption fish has the potential to disrupt reproductive patterns, recruitment and the availability of moonfish resource stocks, where an information on reproductive biology is minimal during the west monsoon. This study aims to analyze the reproductive biology of moonfish in Palabuhanratu Bay. This research was conducted from September 2021 to February 2022 (representing the west moonson), with a sample of 522 fish. Sampling of fish using simple random sampling method. The results show that the sex ratio is 1:0.76 which is dominated by male fish. Moonfish has a negative allometric growth pattern. Spawning season during the study period was in September and October. The reproductive potential ranges from 11.988 to 21.164 eggs. Moonfish spawning patterns indicated total spawners, namely spawning that occurred all at once. The results of the analysis using the Spearman-Karber method showed that femmale’s moonfish reaches the size at first sexual maturity (Lm) is earlier than males.
Keyword: Moonfish, Palabuhanratu bay, Reproductive biology

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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