Judul: The Stock Status of Scalloped Spiny Lobster (Panulirus homarus) in Palabuhanratu Waters Using the Spawning Potential Ratio method
Abstrak: Nelayan Palabuhanratu banyak menangkap lobster terutama lobster pasir (Panulirus homarus). Pendataan yang kurang terkait stok lobster bisa berdampak pada keberlanjutan lobster di perairan Palabuhanratu. Penggunaan metode spawning potential ratio (SPR) bisa menjadi solusi dalam menentukan harvest strategy lobster. Penelitian ini bertujuan untuk mengidentifikasi unit penangkapan lobster, mengidentifikasi komposisi hasil tangkapan lobster, menghitung parameter biologi lobster, dan menentukan status pemanfaatan lobster. Pendekatan length base spawning potential ratio (LB-SPR) digunakan untuk pengolahan data. Analisis deskriptif dan kualitatif digunakan dalam menganalisis data yang didapatkan. Hasil penelitian menunjukkan bahwa kapal yang digunakan untuk menangkap lobster berukuran 2-3 GT dan 5 GT. Alat tangkap berupa gillnet dan trammel net. Lobster yang tertangkap ada 4 jenis yaitu lobster pasir, lobster mutiara, lobster bambu dan lobster batu. Hasil penelitian didapatkan panjang asimptotik (L∞) lobster pasir jantan dan betina sebesar 110,5 mm dan 106,67 mm. Koefisien pertumbuhan (K) untuk lobster jantan dan betina sebesar 0,34/tahun dan 0,44/tahun. Nilai laju eksploitasi (E) lobster pasir jantan dan betina sebesar 0,74 dan 0,80 dengan rata-rata panjang lobster matang gonad (Lm) sebesar 58,21. Nilai spawning potential ratio (SPR) lobster pasir diperoleh sebesar 12,63% dimana hasil tersebut kurang dari 20% yang artinya status pemanfaatan lobster di perairan Palabuhanratu sudah terjadi tangkap lebih (overfishing), In Palabuhanratu, fishers catch a lot of lobsters, particularly the scalloped spiny lobster (Panulirus homarus). The sustainability of lobsters in Palabuhanratu waters may be impacted by inadequate data collection on lobster stocks. Using the spawning potential ratio (SPR) approach will contribute to Harvest Strategy for Lobster Fishery in that area. The objectives of this study are to identify lobster fishing units, characterize lobster captures, compute biological parameters for lobsters, and assess the utilization of lobsters. Data processing uses the length-based spawning potential ratio (LB-SPR) method. The data were analyzed using descriptive and qualitative methods. The findings revealed that the size of the lobster-catching vessels was 2-3 GT and 5 GT. Gillnets and trammel nets are two types of fishing gear. Four different kinds of lobsters were caught: scalloped spiny lobsters, ornate spiny lobsters, bamboo lobsters, and pronghorn spiny lobsters. The findings revealed that the asymptotic lengths (L) of male and female scalloped spiny lobsters were 110.5 mm and 106.67 mm, respectively. Male and female lobsters’ growth coefficients (K) are 0.34 and 0.44 per year. An average scalloped spiny lobster's gonadal mature length (Lm) was 58.21 inches, and its exploitation rate values (E) were 0.74 and 0.80 for males and females, respectively. The scalloped spiny lobster's spawning potential ratio (SPR) value was 12.63%, which is below the 20% threshold, indicating overfishing of the species in the waters around Palabuhanratu.
Keyword: harvest strategy, lobster pasir, Palabuhanratu, spawning potential ratio (SPR), status pemanfaatan

Judul: Dinamika Populasi Lobster Pasir (Panulirus homarus) Dan Lobster Batu (Panulirus penicillatus) Di Perairan Selatan Jawa Barat
Abstrak: Lobster merupakan komoditas penting baik impor maupun ekspor. Permintaan pasar yang tinggi menyebabkan laju penangkapan tinggi sehingga mempengaruhi penurunan populasi. Penelitian ini bertujuan mengkaji status populasi lobster di perairan Selatan Jawa Barat berdasarkan pendugaan parameter dinamika populasi. Pengambilan sampel menggunakan metode penarikan contoh acak sederhana selama bulan Februari hingga Juni 2023. Ukuran panjang karapas lobster berkisar 30-182 mm dengan pola pertumbuhan allometrik negatif. Rekruitmen terjadi sepanjang tahun dengan satu puncak. Ukuran pertama kali tertangkap (Lc50) lobster pasir jantan pada panjang karapas 46,36 mm dan betina pada 49,65 mm, lobster batu jantan pada panjang karapas 50,69 mm dan betina pada 58,82 mm. Ukuran pertama kali mengerami telur (Lr50) lobster pasir betina pada panjang karapas 69,95 mm dan lobster batu betina pada 79,94 mm. Laju eksploitasi lobster betina termasuk kategori optimum dan jantan termasuk kategori overexploited. Rasio potensi pemijahan (SPR) lobster pasir dan batu betina berturut-turut sebesar 12% dan 4% yang mengindikasikan bahwa sumberdaya lobster telah mengalami overfishing., Lobster is an important commodity for both import and export. High market demand causes high capture rates that affect population decline. This study aims to assess the status of the lobster population in the southern waters of West Java based on the estimation of population dynamics parameters. Sampling used a simple random sampling method from February to June 2023. Lobster carapace length ranged from 30-182 mm with a negative allometric growth pattern. Recruitment occurred throughout the year with one peak. First caught size (Lc50) of male sand lobster at 46.36 mm carapace length and female at 49.65 mm, male rock lobster at 50.69 mm carapace length and female at 58.82 mm. The size of the first incubating egg (Lr50) of female sand lobster at 69.95 mm carapace length and female rock lobster at 79.94 mm. The exploitation rate of female lobsters is in the optimum category and males are in the overexploited category. The spawning potential ratios (SPR) of female sand and rock lobsters were 12% and 4%, respectively, indicating that the lobster resource has been overfishing.
Keyword: population dynamics, pronghorn spiny lobster, scalloped spiny lobster, Southern waters of West Java, sustainable

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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