Judul: Rabbitfish (Siganus sp.) Utilization Status in Karimunjawa Waters
Abstrak: Perairan Karimunjawa memiliki potensi perikanan tangkap yang tinggi, baik sumberdaya ikan pelagis maupun karang. Ikan baronang (Siganus sp.) merupakan ikan karang dengan nilai ekonomis penting. Tingginya permintaan konsumsi ikan baronang melatarbelakangi peningkatan operasi penangkapan ikan. Informasi biologi dan status pemanfaatan ikan baronang diperlukan untuk mendukung pengelolaan perikanan berkelanjutan. Tujuan penelitian untuk mendeskripsikan unit penangkapan dan status pemanfaatan sumberdaya ikan baronang serta membandingkan tren status pemanfaatan ikan baronang dalam rentang waktu 2014-2020. Penelitian ini menggunakan data monitoring dari Wildlife Conservation Society (WCS) berupa data panjang ikan baronang. Data yang digunakan sebanyak 2625 ekor ikan baronang dari dua spesies dominan yakni Siganus javus dan Siganus punctatus. Metode pendekatan LB-SPR (Length-based Spawning Potential Ratio) digunakan dalam penelitian ini. Hasil penelitian menunjukkan bahwa unit penangkapan dominan adalah panah dan bubu. Siganus punctatus memiliki nilai SL50 (29,08) < Lm (30) sedangkan Siganus javus memiliki nilai SL50 (27,13) > Lm (23). Siganus punctatus berada dalam status pemanfaatan fully moderately dengan nilai SPR sebesar 33% sedangkan spesies Siganus javus berada dalam status pemanfaatan over exploited dengan nilai SPR sebesar 12%. Oleh karena itu, pengendalian terhadap jumlah tangkapan dan ukuran tangkapan perlu diperhatikan, baik dalam musim penangkapan ataupun musim pemijahan, sehingga terciptanya pengelolaan perikanan baronang yang bertanggung jawab dan berkelanjutan., Karimunjawa waters have potentially captured fisheries resources, pelagic and coral fishes. Rabbitfish (Siganus sp.) is a reef fish with significant economic value. The high demand for the consumption of rabbitfish is the background to the increase in fishing operations. Information on the biology and utilization status of rabbitfish is needed to support sustainable fisheries management. The study aimed to describe the fishing units and utilization status of rabbitfish resources and to compare trends in rabbitfish utilization status in the 2014-2020 time frame. This study used monitoring data from the Wildlife Conservation Society (WCS) in the form of rabbitfish length data. The data used were 2625 rabbitfish from two dominant species, Siganus javus, and Siganus punctatus. The LB-SPR (Length-based Spawning Potential Ratio) approach method was used in this study. The results showed that the dominant fishing units were arrows and traps. Siganus punctatus has a value of SL50 (29.08) < Lm (30), while Siganus javus has a value of SL50 (27.13) > Lm (23). Siganus punctatus is in a moderately utilized status with an SPR value of 33%, while the Siganus javus species is in an over-exploited utilization status with an SPR value of 12%. Therefore, it is necessary to pay attention to controlling the number of catches and the size of the catch, both during the fishing and spawning seasons, to create responsible and sustainable management of the rabbitfish fisheries.
Keyword: length at first maturity, Karimunjawa waters, Siganus javus, Siganus  punctatus, length-based spawning potential ratio

Judul: Management of Rabbitfish (Siganus sp.) Fisheries  Resources in the Waters of Mamuju Bay, West Sulawesi
Abstrak: Tingginya intensitas penangkapan ikan baronang di perairan Mamuju dikhawatirkan dapat mengganggu kestabilan dan pertumbuhannya. Hasil analisis spasial interaksi karakteristik habitat membuktikan bahwa lokasi DPI nelayan baronang di perairan Teluk Mamuju merupakan area nursery ground yaitu tutupan karang dan lamun, terutama area pinggir perairan pada kedalaman 1-2 m. Sehingga dominan hasil tangkapan nelayan berukuran juvenil karena merupakan daerah asuhan ikan baronang berukuran muda. Hasil tangkapan ikan baronang yang ditemukan di perairan Teluk Mamuju ada 3 jenis yaitu ikan baronang lingkis (Siganus canaliculatus) dengan nilai Lm 181,3 mm, ikan baronang batik (Siganus vermiculatus) dengan nilai Lm 177,1 mm dan ikan baronang totol (Siganus guttatus) dengan nilai Lm 204,2 cm. Sebaran layak tangkap ikan baronang secara berurutan yaitu 23,49%, 28,09% dan 16,73%. Status pemanfaatan ikan baronang lingkis, batik dan totol secara berurutan memiliki nilai SPR sebesar 19%, 20% dan 9%. Namun, nilai estimasi SPR ini bersifat sementara dikarenakan kualitas data yang diperoleh sangat terbatas sehingga tidak mampu merepresentasikan secara valid stok populasi ikan baronang di lokasi studi sesuai parameter SPR., The high intensity of Siganids fishing in Mamuju waters potentially threatens the sustainability of its stock. The spatial analysis results of the interaction of habitat characteristics indicate that the location of Siganids fishing ground in Mamuju Bay waters is a nursery grounds, namely coral and seagrass beds, particularly an area of 1-2 m water depth. As a consequence, the catches were dominated by juvenile sized Siganids fish. There were three species of baronang fish found in Mamuju Bay waters, namely white-spotted spinefoot (Siganus canaliculatus) with a length at first maturity (Lm) value of 181.3 mm, vermiculated spinefoot (Siganus vermiculatus) with an Lm value of 177.1 mm, and orange-spotted spinefoot (Siganus guttatus) with an Lm value of 204.2 cm. The distribution of biological allowable catch size (> Lm size) of the fishes were 23.49%, 28.09%, and 16.73%, respectively. The stock status of S. canaliculatus, S. vermiculatus, and S. gutatus was unsustainable, as indicated by the Spawning potential ratio (SPR) values of 19%, 20%, and 9%, respectively. However, this SPR estimation value is still an initial indicator because the quantity of available data was limited. Thus, it could not represent the Siganids fish population in the study site according to the SPR parameter.
Keyword: Siganus, Rabbitfish, Fishing Gear, Length at First Maturity

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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