Java Sea Research Articles

Simulated seasonal oceanographic changes and their implication for the small pelagic fisheries in the Java Sea, Indonesia

Small pelagic fisheries in the Java Sea (JS) contributes to about 26.6% of the total marine fisheries resources, where their spatial-temporal variation is controlled by seasonal oceanographic changes. This study aims to investigate a relationship between seasonal reversal circulation and number of light-fishing vessels (VBD) dispersion that capture small pelagic fishes, using multi-datasets from a regional ocean circulation model, satellite-derived datasets, and pelagic fish landing datasets between 2010 and 2020. The model demonstrates that main axis of eastward (westward) monsoon current that brings warmer and fresher (cooler and saltier) water, confines much closer along the northern Java (southern Kalimantan) during the northwest (southeast) monsoon period. These changes are followed unprecedentedly by southward (northward) shift of VBD and high abundance of euryhaline (stenohaline) fish species. This new evidence implies that reversal monsoon current and surface component of Makassar Throughflow play a significant role on delineating potential small pelagic fishing ground and fish productions.

Fossil Java Sea corals record Laurentide ice sheet disappearance

Abstract The Laurentide ice sheet was the largest late Pleistocene ice mass and the largest contributor to Holocene pre-industrial sea-level rise. While glaciological dates suggest final ice sheet melting between 8 and 6 ka, inversion of sea-level data indicates deglaciation at ca. 7 ka. Here, we present new chronostratigraphic constraints on Laurentide ice sheet disappearance based on Holocene relative sea-level observations from the tectonically stable north coast of Java, Indonesia. Age-elevation data from the flat upper surfaces of 13 fossil intertidal corals (i.e., microatolls) indicate that the Java Sea experienced a relative sea level of 1.3 ± 0.7 m above present between 6.9 and 5.3 ka. To determine uncaptured relative sea-level trends within the observational uncertainties of this apparently constant highstand, we analyzed the internal structure of three sliced microatolls from the same site to produce a high-resolution data set. These data were used to statistically model relative sea-level rates and trends. Employing the data with the model provided evidence for a short-lived rise of relative sea level from 1.0 ± 0.3 m above present at 6.7 ± 0.1 ka to 1.9 ± 0.3 m above present at 6.4 ± 0.1 ka. The end of this rise likely represents the last input of meltwater from the vast Laurentide ice sheet, which, consequently, collapsed at least 400 yr later than assumed by some widely used models of glacial isostatic adjustment. Incorporating these new results into such predictive models will help to better understand the geographical variability of future sea-level rise as a result of global warming.

Sail technology on fishing vessel for blue swimming crab catching application - A review

The increase in fuel prices will gradually have an impact on the capture fisheries sub-sector, especially the fishermen. Sail technology is an alternative that can be used to save fuel oil, although it is realized that this technology cannot completely replace the diesel motor that is commonly used in fishing operations. This study will explain the application opportunities of sail technology on fishing vessels for blue swimming crab (Portunus pelagicus) in the deep waters of the Java Sea. This fishing ground is more than 12 nautical miles from the coast. Using sail technology on fishing vessels is very dependent on the characteristics of wind speed and direction. This discussion explores the relationship between the west and east monsoons in the Java Sea with the direction of fishing trip. Technological difficulties and current challenge in sail technology on fishing vessel for blue swimming crab are identified. The possible ideas for future research in this field are also discussed.

Nitrate and phosphate profiles in the Banda Sea during the northwest monsoon

The Banda Sea (BS) is subjected to monsoonal winds that affected upwelled rich nutrient waters and primary production. However, nutrient characteristic in the region is less constrained. Here, we examine nitrate and phosphate profiles in the Banda Sea from data collected during the northwest monsoon. Waters along the surface density (σθ ) < 22 were dominated by less saline originating from western Indonesia (i. e., Java Sea), accompanied by Indonesian throughflow water Banda (23.0-25.0σθ ) and Banda water (26.5-27.0σθ ), respectively. Surface water was accompanied by low nitrite+nitrate () and phosphate (), meanwhile, the average and concentrations in the upper 500 m were slightly higher in the western part than those in the eastern part suggesting additional sources from upwelled waters. Furthermore, the average nitrite+nitrate to phosphate ratio (N:P ratio) was 11.2:1, indicating nitrogen is a limiting factor for the growth of primary producers, and other sources may play a more dominant role. Two distinct layers in the euphotic zone within different sources and mechanisms namely the nutrient-depleted layer and nutrient-repleted layer were observed. Overall, the result of this study can only be seen as a starting point toward a comprehensive and holistic understanding of the nutrient biogeochemistry of the Indonesia Seas.

Water Security In Tunda Island, Banten Indonesia: Potency &amp; Threat

Water availability and management for water security on small islands are critical. The purpose of this research is to uncover the water resources issue at a small island community level as well as discourse on the potential threats and sustainable management for water security. Tunda Island, located in the Java Sea, is one of 81 small islands in Banten Province, Indonesia. Data were collected through focus group discussions, open interviews with key persons, direct field observations, and secondary data gathering. Moreover, we analyzed time series climate data, particularly rainfall and population growth projections, based on data from official Indonesian government sites. The monthly mean precipitation is ranging from a low of 48 mm/month in August to a high of 292 mm/month in January. A “surplus of water” occurs from November to May, while months with a “deficit of water” occur from June to October. The majority of the community is unaware of the water security issue due to a lack of information and knowledge in the community. Some threats to the sustainability of water resources would be caused by two factors, both anthropogenical and natural: rising water demand, diminishing groundwater reserves due to population growth and tourism activities on the island, drought, sea level rise, and seawater intrusion as climate-related impacts due to increasing population growth and tourism activities on the island and drought, sea level rise and seawater intrusion as climate-related impacts. Developing community knowledge and awareness of water security is the main issue that should be handled first, coinciding with sustainable management practices that consider water use efficiency, the use of alternative water sources (e.g., rainwater harvesting), and protecting and restoring coastal ecosystems, especially for the future tourist destination.

Revitalisasi Dinding Melalui Pembuatan Mural dengan Narasi Sejarah Jamblang, Cirebon

Jamblang Chinatown, Cirebon was once known as a trading city during the Dutch colonial period, as a place for buying and selling and stopping by traders from various regions through the river that flows nearby. The river is a means of transportation that brings ships from the interior of Cirebon to the Java Sea, and vice versa. However, the current situation is reversed because Jamblang is like a "dead city" that is almost forgotten. The government and the community have a dream to revive the Jamblang Chinatown area. Through this PKM activity, a team of lecturers and students of the Faculty of Fine Arts and Design at Maranatha Christian University seeks to revive Jamblang Chinatown by making murals with the surrounding community, as well as providing education as well as performances for the surrounding community through PKM activities. The attraction of making murals containing the historical value of Jamblang. The approach taken is a participatory collaborative workshop with local residents, through mentoring and education. The result achieved is a mural with the theme Mural History Jamblang, which is located on a 90-degree wall and is located in front of Vihara Dharma Rhakita, Jamblang, Cirebon Regency. They participate in the process of making murals. Other residents are interested in knowing the meaning contained in the visualization of the mural. And many are just selfies with a mural as a background. This mural-making attraction is also quite successful as one of the activities that attract public attention during the 2022 Jamblang Festival.

ROB ANALYSIS ON THE COAST OF SEMARANG CITY (CENTRAL JAVA, INDONESIA) ON MAY 23, 2022 BASED ON TIDAL DATA AND INUNDATION DISTRIBUTION

The coast of Semarang City every year always faces flood and tidal problems. Flooding is generally caused by the ongoing rainy season, while tidal flows are caused by rising Java sea levels before the interseason change. This study aims to find the relationship between the tidal incident on May 23, 2022 on the coast of Semarang City with the tidal pattern at the Port of Semarang, and find out the distribution of tidal flows based on the height of inundation in the coastal area of Semarang City. The material used is daily tide data on May 23, 2022, monthly tide data April-May 2022. Data on the distribution of high inundation was obtained based on field surveys and interviews. The results showed that the peak of java sea level elevation occurred on May 23, 2022 with an altitude at the tide staff of 210 cm. Rob occurs almost evenly along the north coast of Semarang City with different heights. The largest tidal height occurred in the Semarang Port Area, which reached a puddle height of 100 cm. There are supposes that the amount of inundation at the site is related to the land subsidence at the site that continues to occur.

Anisakid nematodes from the largehead hairtail fish (Trichiurus lepturus) from the northern coast of Java, Indonesia

Abstract. Setyobudi E, Murwantoko, Utami AMR, Syarifah RF. 2023. Anisakid nematodes from the largehead hairtail fish (Trichiurus lepturus) from the northern coast of Java, Indonesia. Biodiversitas 24: 1560-1568. Hairtail fish has been frequently reported to be infected by anisakid nematodes. This study aims to determine the presence of anisakid nematodes on the large-head hairtail fish (Trichiurus lepturus) from the northern coast of the Java Sea, Indonesia. In total, 306 hairtail fish were collected from the northern coast of Java. Each fish sample was measured its length and weighed, then dissected to examine the presence of anisakid nematode. The anisakid larva examination was conducted in the body cavity, internal organs, digestive tract, and muscles. The anisakid nematodes found were then separated and grouped based on morphological appearance, namely body color and size. Selected samples from each anisakid group and sampling location were extracted and identified molecularly by the direct sequencing method. The findings showed that the larvae of anisakid nematodes infect the T. lepturus with different prevalence and average intensity at each location (P: 38.0-100%, MI: 3.33-42.88 larvae/ind.). Mostly anisakid larvae were found in the body cavity and were not found in the muscle. Most of the T. lepturus from the northern coasts of Cirebon and Pati were infected with anisakid at low intensity (?5 larvae/individual). The high intensity of anisakid larval infection was shown by the hairtail originating from Rembang and Tuban (&gt;20 larvae/ind.). Molecular identification showed that three anisakids were isolated from hairtails from the northern coast of Java, namely Anisakis typica, Hysterothylacium amoyense, and Raphidascaris lophii. Information on anisakid species and their distribution is important as a reference for fish handling and processing, the assessment of the human health risk, and the development of these nematodes as biological tags.

John B. Hattendorf and Pelham Boyer (eds), HM 28: To the Java Sea: Selections from the Diary, Reports, and Letters of Henry E. Eccles, 1940-1942 by Alan M. Anderson

John B. Hattendorf and Pelham Boyer (eds), HM 28: To the Java Sea: Selections from the Diary, Reports, and Letters of Henry E. Eccles, 1940-1942 by Alan M. Anderson

Long-Term Trend and Variability of Volume Transport and Advective Heat Flux through the Boundaries of the Java Sea Based on a Global Ocean Circulation Model (1950–2013)

The variability and trend of volume and advective heat flux, in addition to the net inflow and outflow of advective heat flux in the Java Sea for 64 years (1950–2013), along with its relationship with the monsoon, ENSO (El Niño Southern Oscillation), and IOD (Indian Ocean Dipole), have all been studied. A simulation of the 3D hydrodynamic HYCOM (HYbrid Coordinate Ocean Model) with a 1/8° grid resolution was performed in this study. Judging from the simulated results, the seasonal variability, which has a period of 12 months, has a very significant impact on contributing to the variability and trend of volume and advective heat flux, as well as the net inflow and outflow of advective heat flux in the Java Sea for 64 years. This is followed by interannual variability, which has a time range of 1.5–6.5 years, and interdecadal variability, with a period of 21.3–32 years. The interannual variability in the Java Sea is strongly caused by ENSO and IOD. El Niño and a positive IOD caused a weakening of southward transport through Karimata and the Bangka Strait. On the contrary, southward transport strengthened during La Niña and the negative IOD. Furthermore, La Niña and a positive IOD both strengthen (weaken) the transport westward (eastward) in the Sunda Strait (Eastern Java). On the other hand, El Niño and a negative IOD weaken (strengthen) the westward (eastward) transport in the Sunda Strait (Eastern Java). According to the findings, the IOD effect is stronger than the ENSO effect in the Java Sea. The inflow and outflow of volume transport in the Java Sea are in balance, but not the advective heat flux. The advective heat transported through Karimata and Bangka Strait to the Java Sea is up to 0.216 PW, while the total advective heat flux through the outflow straits (Sunda Strait and Eastern Java) is 0.220 PW. Thus, the net advective heat flux out of the Java Sea is 0.004 PW, allegedly obtained from an atmosphere–sea interaction in which the sea received heat from the atmosphere.

Marine flatworm Acanthozoon sp.-associated bacteria with antibiotic property from the Java Sea

Neglected invertebrates, marine flatworms, have attracted global research interest due to their biological and chemical potential properties. The marine flatworms (Turbellaria), Phylum Platyhelminthes, belong to the Polycladida group. There are about 3000 species of free-living flatworms that make a living by hunting and eating other animals. A marine flatworm Acanthozoon sp. was used in this study due to its abundant presence in the site location. Staphylococcus epidermidis is an opportunistic pathogenic bacterium that was previously considered a harmless skin disease bacterium. This species is now considered to be in the first rank among the causative agents of nosocomial infection, specifically in the form of infections of the urinary tract, respiratory tract, and surgical site wounds. The aims of this study were to explore the biological diversity of marine flatworm-associated bacteria with antipathogenic properties and to detect the presence of polyketide synthase (PKS) and nonribosomal peptide synthetase NRPS gene clusters through a molecular approach. Recent studies have shown that S. epidermidis undergoes functional changes in the pro-inflammatory peptide family so that it has functions in immune evasion and biofilm development. Therefore, the search for new antimicrobial compounds is urgently needed due to the limited choice of antibiotic use. In the preliminary screening by overlay test, 7 out of 17 (41.2%) isolates showed antibacterial activities. These isolates were reselected and their activity confirmed by using plug agar and disk-diffusion methods. The FA02, FA03, FA05, FA07, FA13, FA16, and FA17 isolates demonstrated their inhibitory activities consistently against the causative agent of nosocomial infection S. epidermidis. Based on the morphological and 16S rRNA partial sequencing analysis, these isolates were closely related to the genus Virgibacillus, Brevibacterium, Alcanivorax, and Vibrio. None of these seven antibacterial strains possesses PKS-I and PKS-II, except NRPS genes for Virgibacillus salarius strain FA02, V. salarius strain FA16, and V. salarius strain FA17. The results of this study showed that bacteria associated with marine flatworms have future potential as a source of promising natural products for the development of antibiotics.

The fate of mangrove ecosystem sustainability on the shrimp cultivation area in Tulang Bawang District, Lampung, Indonesia

The exploitation of mangrove forests for economic purposes is rampant in tropical countries nowadays, particularly for shrimp farming, such as in the Lampung green belt in the front of the Java Sea. So, ensuring the sustainability of existing mangroves is the need of the hour. In view of above, this study aims to analyze the sustainability index of mangrove ecosystem management and the sustainability status of the mangrove ecosystem from the ecological, economic, social, and institutional dimensions using the Multidimensional Scaling (MDS) method through the Rapid Appraisal for Fisheries (RAPFISH) approach in East Rawajitu Sub-district, Tulang Bawang District, Lampung Province, Indonesia. The analysis revealed that mangrove ecosystem management’s sustainability index was categorized as ‘less sustainable’ (index 43.01 out of 100). Meanwhile, the social dimension (51.65) was categorized as ‘quite sustainable’, and other dimensions (ecological, economic, and institutional) were ‘less sustainable.’ Therefore, it is proposed that further development of the social dimension is a strategic way to develop the other three sustainability dimensions to achieve ecosystem sustainability as a whole in the study area. Alternative strategies that can be applied for sustainable management of mangrove ecosystems in East Rawajitu Sub-district, Tulang Bawang District are increasing coordination between stakeholders, creating formal regulations, increasing the productivity and creativity of Ikatan Istri-istri Petambak Dipasena (ISTANA), formulating an integrated mangrove ecosystem management plan program, undertaking rehabilitation efforts, increasing the role of mangrove groups, and increase the attention of researchers.

Amplitude modulations of seasonal variability in the Karimata Strait throughflow

The Karimata Strait (KS) throughflow between the South China Sea (SCS) and Java Sea plays an essential role in heat and freshwater budget in the SCS and dual roles in strengthening/reducing the primary Indonesian throughflow (ITF) in the Makassar Strait. A sustained long-term monitoring of the ITF is logistically challenging and expensive; therefore, proxies are needed. Here, we use a combination of in situ measurement of the KS throughflow and satellite-derived sea surface height (SSH) and sea surface wind (SSW) to determine the interannual and decadal modulations in seasonal amplitude of the KS throughflow associated with El Niño-Southern Oscillation (ENSO), Indian Ocean dipole (IOD), Pacific Decadal Oscillation (PDO). Linear regression, correlation, harmonic and power spectrum analyses are used. The results manifest that there are significant interannual to decadal modulations in the seasonal amplitude of the KS throughflow. The modulations of the seasonal amplitude in the volume and heat transports range 1.36-1.92 Sv (1 Sv = 106 m3 s-1) and 126.41-173.36 TW (1 TW = 1012 W), respectively, with a significant cycle of ~9 years. From 1994 to 2020, the seasonal amplitude of volume transport through the KS shows an increasing trend of 37.75 ± 15.69 mSv decade-1 (1 mSv = 103 m3 s-1). The seasonal amplitude of the heat transport also increases, at a rate of 4.78 ± 1.52 TW decade-1. The KS volume transport is positively correlated with PDO and ENSO indices (r2 = 0.69 and r2 = 0.58), with a lag of 12 and 10 months, respectively. The results of composite analysis suggest that the interannual variability of the KS transport is related to the interannual anomalies of the SSH gradient and the local SSW fields in boreal winter.

Challenging the Freedom of the Ocean: The U.S. Freedom of Navigation Program in Indonesian Archipelagic Waters

INTRODUCTION. In 2017, the US Department of Defense issued its Annual Freedom of Navigation Report. This is the first report released by the US government under the Trump administration. The report listed the geographic location of the US Freedom of Navigation (“FON”) Program all over the world. This document briefly describes an excessive maritime claims by coastal states’ activities in each case. Besides the South China Sea, the main US concern in Asia is Southeast Asia, which became one of the playing fields for the US FON Program, in particular the Java Sea in Indonesian archipelagic waters. MATERIALS AND METHODS. This article examines the US DoD’s Annual Freedom of Navigation Report for Fiscal Year 2016 and the provisions of Indo­nesian national legislation. Further, the author analyses the applicable rules of international law, such as the relevant provisions of the UN Convention on the Law of the Sea (“UNCLOS”). In this research, the author relies on the existing doctrine on the legal issues underlying the topic of the article. The methodological basis consists of general scientific and special research methods, including analysis, synthesis, and systematization, as well as formal-legal, formal-logical and critical-legal methods.RESEARCH RESULTS. This article argues that the US FON Program in Indonesia is not about the partial submission of archipelagic sea lane passage but rather the controversy created by Indonesian national legislation. In particular, when Indonesia’s government requires prenotification and prohibits aircraft to come across the route normally used for international navigation. Therefore, this paper seeks to evaluate what are the different views between Indonesia and the US in terms of the regulatory framework in the Java Sea and what could be done in addressing these issues.DISCUSSION AND CONCLUSIONS. The root of the disagreement between the US and Indonesia is in diverging interpretations of Article 53(1) of the UNCLOS; more specifically, whether this Article creates an obligation for archipelagic States to establish archipelagic sea lanes passages. In the author’s opinion, this disagreement should be resolved through bilateral negotiations aimed at elaborating a common understanding. Furthermore, the exercise of freedom of navigation should not infringe upon the coastal State’s rights, including its sovereignty.

Seasonal variation of mixed layer depth and thermocline thickness from the ctd argo float data in the Southern Makassar Strait

The Makassar Strait (MS) is directly connected to the Sulawesi Sea in the north and the Java Sea and the Flores Sea in the south and is the main route of Indonesia Throughflow(ITF). Hence Stratification of water mass in the MS is influenced by the dynamics of these waters. This study aims to describe seasonal variations of the mixed layer depth and the thermocline thickness, identify ITF water masses, and the occurrence of coastal upwelling in the southern part of the MS. The results show that the North Pacific water origin of North Pacific Subtropical Water (NPSW) and North Pacific Intermediate Water (NPIW) are dominant, with a maximum salinity characteristic of 34.6-34.7 psu in the thermocline layer and a minimum salinity of 34.5 psu in the intermediate layer. However, near-surface fresh Java Seawater appears to be dominant during the northwest monsoon (NWM-DJF) period. Seasonal variation of the mixed layer depth is much deeper (93m) and vertical gradient of temperature and salinity are much stronger due to the presence of fresh Java Sea water advected by the eastward Java Monsoon Current. However, during the southeast monsoon (SEM-JJA) period the mixed layer depth is much shallower and the thermocline layer is much thicker (198 m), Associated with much stronger ITF and upwelled colder water from the upwelling area. The coastal upwelling event during the SEM period in the study are is characterized by an increase of isotherm of 25 °C, isohaline of 34.0 psu, and isopycnal of 22.0 kg/m3 from about 75 m depth to the sea surface layer.

Analysis of the level of environmental friendliness of fishing gear gill nets in Java Sea waters, Bangkalan Regency, East Java, Indonesia

Fish is one of the resources that can recover (renewable resources) but if the use and management are carried out irrationally in the long term these fish resources are feared to be extinct, therefore it is necessary to manage fish resources responsibly and sustainably. Gill nets or in the world of international fisheries better known as "gillnet" are fishing devices in the form of rectangular mesh sheets with the same size mesh and equipped with buoys, ballasts, upper ropes and with or without bottom ropes to block the swimming direction of fish, so that the target fish will be entangled in the net or bounced on body parts dragnet. The method used in this study is a descriptive method, namely direct observation in the field and interviews with fishermen and secondary data followed by determining the sample population and random sampling. The purpose of this study is to analyze variability, selectivity and determine the level of environmental friendliness of folding bubu type fishing gear in Java Sea Waters, Bangkalan Regency. The results of the study obtained variability and selectivity of gill net catches with the main catch (main catch) is crab (Portunus pelagicus) as much as 118 kg or 76.4% of the total catch and bycatch (by catch) is crab (Scylla sp.)as much as 7.8 kg or 5.1%, Gulama Fish (Johnius trachycephalus) as much as 10.5 kg or 6.8%, Tongue Fish (Cynoglossus arel) as much as 10 kg or 6.5% and Manyung Fish (Arius thalassinus) as much as 8 kg or 5.2% of the total catch while the catch is wasted (discard)) none. Thelevel of environmental friendliness of crab net type fishing gear obtained an assessment score of 26.8 which shows that this type of fishing gear is classified as Environmentally Friendly fishing gear.

The Outstanding Value of a Cultural Heritage: The Old City of Semarang as the Center for Global Trade in Java, Indonesia in the 18th – 20th Centuries

Semarang Old City is located in Semarang City, Central Java, Indonesia. This article contains the discussion on the history of Semarang Old City as the center of global trade activities. This Old City was founded at the end of 17th century after an agreement was approved by the Mataram Kingdom and the Vereeniging van Oost-Indische Compagnië (VOC/The Dutch East Indie Company) in 1678, that led VOC to take control over the north coastal region of Java from the Prince of the Mataram Kingdom, Amangkurat II. Based on this agreement, VOC was given the right to choose the areas near the center of Semarang Regency and Semarang River as its residence in order to easily control the Javanese administration and the Java Sea trading activities. Later on, the colony of the VOC developed into a little city surrounded by a fortress in which the VOC leaders, its officers, and soldiers resided, and some city’s facilities were built such as municipality house (stadshuis), trading offices, shops, roads, soldier barracks, warehouses, schools, hospital, church, court, prison, and residential areas. In the Dutch Colonial era (18th – 20th centuries), this old city become the center of international trade activities in Central Java strengthened by the presence of Semarangs Handels Vereeniging (Association of Traders in Semarang) and Nederlandsche Handels Maatshappij (Dutch Trade Company), which managed the import-export trade.

A response to article “Java sea Spirulina platensis chemical analysis and its protective ability against H2O2-exposed umbilical cord mesenchymal stem cells according to CD73, CD90, and CD105, viability, and HIF-1 alpha docking” (Letter)

Journal of Applied Pharmaceutical Science (JAPS): A new open-Access international journal in the field of Pharmaceutical ScienceDr. Khalid Akhter Ansari

The ocean response to El Nino Southern Oscillation (ENSO) in the Bali Sea: a model study

The Bali Sea (BS) is connected to the Java Sea and Makassar Strait in the north and is one of the main outflow straits of the Indonesian Throughflow (ITF) in Lombok Strait (LS). Local ocean dynamics and their variability may be controlled significantly by the ITF. This study aims to investigate the interannual variation of circulation, mixed layer depth, and isotherm of 20°C, by performing a simulation of fine- a resolution 1/84° ocean circulation model of CROCO between 2010-2020 with a focus on El Nino 2015 (EN2015) and La Nina 2020 (LN2020) events. The model validation reproduces well the satellite-derived SST and SSH dataset with a correlation coefficient of >0.9. The model demonstrated an anti-clockwise circulation of the ITF in the BS, entering via the northern and exiting into the LS via the southern area. This circulation changes drastically during the ENSO event, where the ITF transport inflow is weaker and shallower during EN2015, compared to a much stronger and deeper ITF inflow during LN2020. Accordingly, shallower mixed layer depth and depth of isotherm of 20°C are found during EN2015, and vice versa. Coherence of these parameters with NINO3.4 is very significant (>-0.89) with a phase lag of 1.7 months.

Population Dynamic Parameters and Length Based Spawning Potential Ratio (LB-SPR) of Red Snapper (Lutjanus malabaricus) in The Eastern Java Sea

Decision in fisheries management must be made based on the best scientific evidence available. In the poor data fisheries, the fish length data can be useful to determine the status of fish population after its exploitation. The target species of the studied fisheries is the red snapper (Lutjanus malabaricus) in the eastern Java Sea. This study aims to analyze the stock status of red snapper in the eastern Java Sea using Length Based Spawning Potential Ratio (LB-SPR) method. Data collection was done from November 2020 until April 2021. This study separated the analysis of the population dynamic parameters between male and female fish. The growth parameters of male fish was Lt = 92.20 (1 – e−0.27(t-0.07)), with natural mortality (M) of 0.35, fishing mortality (F) of 0.63, and total mortality (Z) of 0.98 per-year. Whereas for female fish, Lt = 91.09 (1 – e−0.29(t-0.44)), with M of 0.38, F of 1.40, and Z of 1.78. The exploitation rate (E) for males was 0.64, and for the female was 0.79. The spawning potential ratio (SPR) was 17%, below the limit reference point of 30% SPR. The current utilization rate of the red snapper in the eastern Java Sea must be reduced to ensure its sustainability.