Judul: Spatio-Temporal Utilizations, Environmental Parameters and Diversity of Grouper in Saleh Bay
Abstrak: Saleh Bay is a fishing area for local people, especially fishermen in Sumbawa and its surroundings. One of the reef fish resource commodities caught is grouper. However, the productivity of reef fish and demersal fish in Saleh Bay has decreased, leading to an overfishing status. Fishermen catch fish on a large scale, juvenile-sized grouper are caught, and there are indications of catching fish using fishing gear that is not environmentally friendly, such as bombs and potassium. In addition, several locations in the waters of Saleh Bay have been designated as marine conservation areas, so monitoring the utilization of the grouper fish resources is necessary. Therefore, this study aims to identify grouper fishing units, grouper utilization status and grouper fishing intensity in each fishing area, analyze grouper diversity (Shannon-Wiener index, Simpson index, Margalef index, and Pielou index), and the condition of environmental and ecological parameters of grouper in Saleh Bay. This research was conducted in Saleh Bay, Sumbawa, West Nusa Tenggara, sample were taken from February to April 2021. Data on fish landings used included production, number of individuals, fishing gear, fishing effort, and coordinates of fishing areas. The environmental parameter data used is AQUA MODIS satellite image data, including sea surface temperature, chlorophyll-a, and currents. The analytical techniques in this study are descriptive analysis, catch per unit effort, spatial-temporal analysis, the diversity indices (Shannon-Wiener index, Simpson index, Margalef index, and Pielou index), and trophic level. The results show that the grouper fishing fleet in Saleh Bay is a small-scale fishery with fishing gearsuch as bottom longline, troll-line, hand-line, and speargun. The trend of grouper resource utilization tends to increase, and fishing efforts positively influence grouper production in Saleh Bay. Based on CPUE and Fishing Power Index values, the order of the most effective fishing gear used to catch grouper is bottom longline, troll-line, hand-line, and speargun. The grouper fishing ground carried out by fishermen is divided into several locations: Liang Island, Ngali Island, Dempu Island, Lipan Island, Raft Island, and Nusa Pudu Island. The highest fishing intensity occurred around Liang Island, Ngali Island, and Rakit Island. The high intensity of fishing was indicated by the number of fishing operations and the CPUE value in the fishing ground. In the long term, it can lead to the degradation of the grouper population. In addition, fishermen are still catching fish around Liang Island, Lipan Island, and Rakit Island, some of whose water areas have been designated conservation areas. So, increasing supervision in managing grouper fisheries in Saleh Bay is necessary. The environmental conditions of the waters consisting of currents, sea surface temperature, and chlorophyll-a indicate that from July to September, the waters of Saleh Bay experienced an increase in water fertility. The sea surface temperature from July to September ranges from 27.9℃ to 29.4℃. The chlorophyll-a concentration from July to September ranged from 0.13mg/m to 9.05 mg/m³. Fertile waters will be used by phytoplankton, phytoplankton is eaten by zooplankton, small fish eat zooplankton, and small fish eat by big fish to top predators to create a food chain in these waters. Groupers were top
Keyword: Catch per Unit Effort, Fishing Ground, Grouper, Spatial-temporal, Saleh Bay

Judul: Improving the Understanding of Small-scale Grouper and Snapper Fisheries in Saleh Bay-West Nusa Tenggara, Indonesia to Enhance Their Management
Abstrak: Groupers (Serranidae: Epinephelinae) are a crucial component of fisheries in coastal tropical and sub-tropical regions, providing essential protein and supporting livelihoods. While global landings of grouper have been steadily increasing, with China and Indonesia contributing over 60% of the total catch, challenges persist in managing their stocks, particularly in small-scale fisheries in developing nations. This study aimed to propose an effective management strategy for key grouper species in Saleh Bay, West Nusa Tenggara, Indonesia by addressing knowledge gaps and evaluating different management options. Specifically, this involved understanding the dynamics of these fisheries, including fishing methods and the composition of their landings, examining the life history and stock condition of a key but previously data-poor grouper species, i.e., brown-marbled grouper Epinephelus fuscoguttatus, and critically evaluating various management procedures using the Method Evaluation and Risk Assessment (MERA) tool. Findings reveal that 57.7% of the total catches of small-scale reef and demersal fisheries in Saleh Bay consisted of grouper and snapper (Lutjanidae). The fishery is complex, with eight fishing methods employed to catch 75 species. Four species, namely the leopard coral grouper (Plectropomus leopardus), orange-spotted grouper (Epinephelus coioides), spotted coral grouper (Plectropomus maculatus), and malabar blood snapper (Lutjanus malabaricus) were primarily targeted, using three main fishing methods, i.e., bottom longline, speargun, and handline, together accounting >90% of the total catch. The composition of catches using these methods changed significantly with fishing depth, season, and/or year. Fishing activities follow a temporal pattern influenced by monsoonal seasons, and fishers utilized specialized tactics to target high-value species for maximum profit. Preliminary biological studies and data from the fish landing monitoring program were used to re-evaluate the spawning potential ratio (SPR) of E. fuscoguttatus. This is one of 12 species targeted for management in Saleh Bay, and of concern as the SPR was previously estimated to range from only 0.05 to 0.07, well below the reference SPR limit of 0.20 and target of 0.30. A new estimate of L50 (length at which 50% of the population is mature) was derived which is ~100 mm smaller than the previous estimate. This new L50 estimate, when combined with the length-based SPR, yielded higher SPR estimates (0.11 to 0.25), although still below the target SPR. Finally, the study employs the MERA approach to assess management procedures for P. leopardus in Saleh Bay. Results indicated that the current size limit and spatial closure regulations may be ineffective due to low compliance and the limited extent of no-take zones within marine protected areas in Saleh Bay, which are smaller than the home range of this species. Recommendations for enhancing the sustainability of grouper and snapper fisheries in Saleh Bay include exploring total allowable catch controls, implementing seasonal closures to limit fishing effort, strengthening existing regulations, and conducting further studies on life-history aspects and stock assessment. In summary, this study underscores the significance of thoroughly understanding the dynamics of small-scale fisheries and the necessity for adaptive management strategies that align with specific local contexts. Sustained collaboration among researchers, fisheries managers, and stakeholders is crucial for tackling management challenges and enforcing effective management to ensure the
Keyword: small scale fishery, fishing dynamic, data limited fishery, method evaluation and risk assessment, management strategy evaluation, brown-marbled grouper, leopard coral grouper

Judul: Invers dari Matriks Tridiagonal Jacobi
Abstrak: Suatu matriks berukuran n×n dinamakan matriks tridiagonal jika untuk . Karya ilmiah ini memberikan algoritma yang mudah untuk menemukan invers ( dari matriks tridiagonal Jacobi yang simetrik dan nonsimetrik. Setiap elemen pada matriks tridiagonal ini adalah bilangan real. Terdapat 3 lema dan 2 teorema untuk menentukan . Lema pertama menunjukkan persamaan utama dalam membuktikan lema-lema dan teorema-teorema selanjutnya. Invers dari matriks yang simetrik dibuktikan oleh lema kedua yang menunjukkan elemen-elemen baris ke- dari . Selanjutnya, lema kedua dilengkapi dengan teorema pertama yang menunjukkan elemen-elemen dengan . Invers dari matriks yang nonsimetrik dibuktikan oleh lema ketiga yang menunjukkan elemen-elemen dengan dan elemen-elemen dengan dibuktikankan oleh teorema kedua.
Keyword: symmetric, nonsymmetric, matrix