Judul: Characteristics of Lobster Fishing Ground Based on Biological and Technological Aspects in Palabuhanratu Bay
Abstrak: Penurunan produktivitas tangkapan dan pengurangan ukuran panjang (size) lobter yang ditangkap nelayan di Palabuhanratu dewasa ini kemungkinan disebabkan oleh perubahan lingkungan perairan dan tekanan teknologi penangkapan ikan yang cenderung memanfaatkan lobster secara besar-besaran. Namun informasi tersebut masih terbatas akibat aktivitas riset yang belum dilakukan. Terbatasnya informasi tentang daerah penangkapan. Tujuan penelitian ini yaitu menentukan karakteristik daerah penangkapan lobster berdasarkan aspek biologi dan teknologi serta memetakan daerah penangkapan lobster potensial. Data yang dikumpulkan antara lain produksi unit penangkapan jaring insang dasar, trammel net, dan pancing selama penelitian, ukuran panjang karapas dan berat lobster, jenis dan metode pengoperasian alat tangkap, spot penangkapan, kondisi armada. Data jenis, metode pengoperasian alat tangkap, dan kondisi spot penangkapan diperoleh melalui wawancara teknik purposive sampling. Hasil penelitian menunjukkan nelayan di Teluk Palabuhanratu mengoperasikan alat tangkap jaring insang dasar, trammel net dan pancing untuk menangkap lobster. Hasil tangkapan lobster yang sesuai dengan ukuran layak tangkap adalah lobster pasir sebanyak 80,4%; lobster mutiara sebanyak 60%; dan lobster bambu sebanyak 68,4%. Evaluasi daerah penangkapan lobster berdasarkan aspek teknologi terhadap alat tangkap dan metode penangkapan adalah pancing, sedangkan terkait armada penangkapan trammel net lebih baik. Daerah penangkapan lobster terdiri dari 6 zona penangkapan. Zona penangkapan lobster potensial yaitu zona Cimaja., The decline in catch productivity and reduction in the length (size) of lobster caught by fishermen in Palabuhanratu today is probably due to changes in the aquatic environment and pressure from fishing technology which tends to use lobsters on a large scale. However, this information is still limited due to research activities that have yet to be carried out—limited information about fishing areas. This study aimed to determine the characteristics of lobster fishing grounds based on biological and technological aspects and map potential areas. The data collected included the production of fishing units for gillnets, trammel nets, and hand line during the study, the size of the carapace length and weight of the lobsters, the type and method of operating the fishing gear, the fishing spot, and the condition of the fleet. Data on species, operating method of fishing gear, and fishing spot conditions were obtained through purposive sampling technique interviews. The results showed that fishermen in Palabuhanratu Bay operate gillnets, trammel nets, and hand lines to catch lobsters. The catch of lobsters according to the proper size for catching were sand lobsters, as much as 80.4%, pearl lobsters, as much as 60%, and bamboo lobsters, as much as 68.4%. Evaluation of lobster fishing areas based on technological aspects of fishing gear and fishing methods is hand lines, while the trammel net fishing fleet is better than other gear. The lobster fishing area consists of 6 fishing zones. The potential lobster-catching zone is the Cimaja zone.
Keyword: catch size, fishing ground, lobster, Palabuhanratu

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: 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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