Strait Waters Research Articles

Evaluation of ecological health of Hainan Island inshore waters in the South China Sea based on preliminary fish biotic integrity index (Actinopterygii and Elasmobranchii)

The well-being of marine ecosystems significantly influences biodiversity and ecological equilibrium amidst pressing challenges such as overfishing, water pollution, and climate change. Drawing upon data from two fishery stock surveys conducted in the inshore waters of Hainan Island in 2022, this study undertook a comprehensive evaluation of the marine ecosystem’s health status in the region. Employing the Fish Index of Biological Integrity (F-IBI) analysis method, coupled with an examination of the structural and functional aspects of the fish community, our research sheds light on the prevailing conditions. Our study revealed a spatial dichotomy within the fish communities of the study area and delineated them into two distinct groups: the northwestern and southeastern ones, with evident disparities in community structure between the two. By employing indicator screening and calculation, we segmented the fish health index in the inshore waters of Hainan Island into five tiers. Despite discernible anthropogenic influences, the ecological health of these waters remained generally robust. Notably, the mean F-IBI of fall (56.30) significantly exceeded that of spring (48.16) (P < 0.01). Furthermore, regarding spatial distribution, the ecological well-being of the southeastern waters surpassed that of the northwestern and Qionghzhou Strait waters. This study represents a pioneer endeavor to apply ecological health assessment methodologies towards informing resource management and conservation strategies for the inshore fisheries of Hainan Island. By furnishing a scientific foundation, our research contributes to the pursuit of sustainable marine ecological development within this locale.

Pemanfaatan Sumber Daya Alam Pasir Laut sebagai Komoditas Tambang Masyarakat di Perairan Kabupaten Karimun, Kepulauan Riau

Potential mining commodities in Karimun Regency, Riau Islands Province, include: tin, granite, land sand and sea sand. Areas in Karimun Regency that have the potential for sea sand are Babi Island Waters, Meral District, Karimun Regency and Tulang Village Waters, Selat Gelam District, Karimun Regency. This study was carried out to measure the optimal level of utilization of natural sea sand resources that can guarantee its sustainability. This is done by measuring the level of availability of sea sand; and measuring available sea sand reserves, the level of utilization that does not erode reserves, as well as estimated supply projections for future needs. The method used is the observation method, by collecting field data. Data were analyzed descriptively, with bathymetry measurements, spatial analysis using Geographic Information Systems (GIS), and literature study. The resources of the Community Mining Area with sea sand as a commodity in area A of Babi Island waters are 1,174,626.58 m3 and the resources of the Community Mining Area in area B of Gelam Strait waters are 502,088.58 m3

Spatial and Temporal Effect of Environmental Factors on the Length-Weight Relationship of the Bali Sardinella (Sardinella lemuru Bleeker, 1853) in Bali Strait Water

Spatial and Temporal Effect of Environmental Factors on the Length-Weight Relationship of the Bali Sardinella (Sardinella lemuru Bleeker, 1853) in Bali Strait Water

Spatial Distribution of Nutrient in The Waters of Haruku Strait, Central Maluku Regency, Maluku Province

Strait waters are influenced by tides, water masses and surrounding land. This study aims to analyze the spatial distribution of nutrients in the waters of the Haruku Strait, Central Maluku Regency, Maluku Province. The research method used is the survey method by taking water samples. Water samples were taken from 17 observation stations spread across the Haruku Strait at depths of 1 meter, 25 meters and 50 meters using the Niskin Bottle Water Sampler. Nitrate concentration analysis using the OPTIZEN Alfa equipment (Spectrophotometer UV-Vis) and the Brucine Sulfate method (SNI: 06-2480-1991) and phosphate concentration analysis using the Ammonium Molybdate method (APHA 10th ed. 5400-PD, 1998). The time of observation took place on July 23, 2022. The results showed that the average concentration of nitrate at a depth of 1 m was 1.146 ± 0.647 mg/L, a depth of 25 m was 1.148 ± 0.709 mg/L and a depth of 50 m was 1.136 ± 0.701 mg/L while the average concentration of phosphate at a depth of 1m was 0.051 ± 0.028 mg/L, a depth of 25 m was 0.053 ± 0.029 mg/L and at a depth of 50 m was 0.049 ± 0.020 mg/L. The waters of the Banda Sea, the Seram Strait and contributions from the rivers on the coast of Ambon Island play a role in the distribution of nutrients in the waters of the Haruku Strait.

Pelatihan Pengoperasian Alat Magnetometer untuk Identifikasi Ranjau dengan SATRAN ARMADA II TNI-AL di Selat Madura

Magnetometer Operation Training for Mine Identification with G-882 Magnetometer equipment and the use of the SonarWiz software application in the Madura Strait is a training initiative that aims to increase the knowledge, skills and capabilities of Mine Ship Unit (STRAN) personnel of the TNI-AL ARMADA II in operating the tool. magnetometer to detect and identify mines in the waters of the Madura Strait. In this training, participants will be given an in-depth understanding of the working principle of the magnetometer, correct operating techniques, and magnetic data analysis methods to identify anomalies that indicate the presence of mines. In addition, participants will also be trained in operating the G-882 Magnetometer and using the Sonar Wiz software application, this support system that strengthens mine detection and identification capabilities. The proposed solution is through intensive training which includes theory sessions, field practice, processing of magnetometer data and which bombs can be identified and simulation of real situations for the 0.5-5 (nT) classification including 16m depth bombs and 1-5 (nT) including bombs. with a depth of 30m. Participants will be actively involved in practicing the operation of the magnetometer device, data analysis, and interpretation of results to increase their understanding of the characteristics of mines in the Madura Strait waters. It is hoped that this training will produce positive outcomes, such as increasing the knowledge, skills and confidence of Mine Ship Unit (STRAN) II TNI-AL personnel in operating the magnetometer device for mine identification. In addition, it is hoped that there will also be close cooperation between Mine Ship Unit (STRAN) personnel from the Indonesian Navy and the people of the coastal areas in supporting the task of securing the waters of the Madura Strait.

Asymmetrical individual both left and right otoliths of Tuna Scombrini collected from the Java Sea

Otolith can be used as a natural marker of fish stock or anomalies between individuals within fish stock. This research aims to study the relationships between fish length and otolith length and confirm differences in otolith shape between species in the Scombrini tribe and Carangidae family (Decapterus ruselli). Sample used in our analysis were collected around July - September 2023 from three different location, Rastrelliger brachysoma (Lekok waters, Pasuruan), Scomber australasicus (Bali Strait waters) and Decapterus ruselli (Sendang Biru, South Malang). Total 96 specimens were identified based on morphological character as Rastrelliger brachysoma, Scomber australasicus and Decapterus ruselli. Each of following samples were cut horizontally at the frontal head to open the skull and remove sagitta otolith below the hindbrain using dissecting set, then cleaned and stored dry in microtube 1,5 ml separately for left and right to further documented using Celestron Digital Microscope Pro Gray USB 44308. Otolith morphometric data collected includes maximum length using TpsDig and weight using analytical balance. The relationship between Forked Length (FL) and otolith length, length-weight relationship of otolith was determined using simple linear regression on software Statistical Product and Service Solutions (SPSS). Paired sample t-test was applied to determine asymmetrical size of left and right otoliths. In this study, it was found that the shape of the otoliths between species has differences in the rostrum, antirostrum, ventral and dorsal parts. FL-otolith length relationship of S. australasicus, R. brachysoma and D. ruselli are Y=0,725+0,164X, r2= 0,519; Y=0,191+0,230X, r2= 0,911; Y=3,156+0,075X, r2=0,071 respectively. The LW sagitta relationship shows that there is a very strong relationship (P<0,05) between L and W of otoliths. The results of the Paired Sample T-test showed that there was no significant difference in the size of the left and right otoliths (Sig>0.05). Otolith shape is influenced by fish behaviour, diet and environment and it may be used as additional information to distinguish between tribe or even species. Otherwise, its asymmetric relationship and LW relationship may be potential new methods for stock discrimination and have other implications such as stock assessment, understanding natural asymmetry, and its potential applications in fisheries management and conservation.

The Urgency of Handling Illegal, Unreported and Unregulated Fishing in the Indonesian Border Region Perspective: Marine Security in the Makassar Strait

ASEAN Outlook on Indo-Pacific (AOIP) plays a role in maintaining peace, security, stability and prosperity in the Asia Pacific and Indian Ocean (Indo-Pacific) region. However, due to common and competing interests, there are still conflicts in the region's implementation. Maritime security cooperation, which includes addressing illegal, unreported, and unregulated (IUU) fishing, is one of the most important issues in the ASEAN region. The research intends to examine law enforcement against IUU violations in the ASEAN region, as well as the consequences of IUU violations by ASEAN countries on waters in the Makassar Strait. This is a qualitative study that employs a normative-empirical approach. The first problem is analyzed using the normative aspect, which is based on international and national law on ASEAN agreements on IUU, law enforcement, and other issues. While the empirical aspect is used to analyze the second problem through in-depth interviews about Makassar Strait water supervision and law enforcement. Based on the research findings, IUU law enforcement in the ASEAN Region must be carried out firmly to parties that threaten security and stability in the ASEAN Region, as outlined in each agreement participant's national law. Meanwhile, the legal consequences of IUU violations in the ASEAN Region have an impact on the security and stability of the waters of the Makassar Strait.

Analysis of Currents in Open Water Southwest of Lae Lae Island

Ocean currents are one of the movements of horizontal or vertical mass movement of seawater that takes place continuously. The purpose of this study is to determine current conditions in open water close to narrow strait waters, as well as canal estuaries. Current data is the result of measurements that have been carried out using ADCP (Acoustic Doppler Current Profiler) mini type ADP-SONTEK equipment on May 16, 2018, while tidal data refers to the recording results of the Makassar BIG tidal station. The results showed that the total surface current speed ranged from 0.017 – 0.375 m/sec with a dominant direction to the west or to open water both at high tide and at low tide. While the result of separation, the speed of tidal currents ranges from 0.032 – 0.343 m / sec.

MODELING THE DYNAMICS OF DISSOLVED OXYGEN CONCENTRATION IN WATERS OF THE ANIVA BAY (THE SEA OF OKHOTSK)

To determine the risks for mariculture farms, the intra-annual change of dissolved О2 concentration was simulated for five zones in the Aniva Bay using the CNPSi model. Zone 1 differed sharply from other zones as the most shallow and freshened. Zone 2 is characterized by a pronounced water exchange with Zone 3 and Zone 4: during spring two layers were formed and stood out in these zones, in the summer the water column was homogeneous. Zone 3 has free water exchange with the open waters of the La Perouse Strait. An outstanding feature of Zone 4, in the deep-water part of the bay, was a distinctive subsidence of waters in the centre of the anticyclonic circulation and the maximum thermocline depth (up to 60-70 m). Zone 5 extends along the western coast of the Tonino-Aniva Peninsula and is characterized by the constant upwelling of waters during the icefree period, which is clearly expressed by lower water temperatures. The calculation showed that in the areas suitable for mariculture farms coastal waters were provided with oxygen throughout the year. Anaerobic conditions developed in spring only in the deepest parts of the bay. An additional source of oxygen in the Aniva Bay is natural thickets of macrophytes, among which the Japanese saccharin (Saccharina japonica) dominates in terms of biomass and area. Annually, Japanese saccharin itself absorbed at least 1200 tons of C in its biomass and supplied at least 3100 tons of О2. Unlike the artificially grown biomass, the biomass of all macrophytes would remain in the system and be destroyed during the life cycle, and the oxygen would be consumed for oxidation. The carbon accumulated in the biomass would again return to the rapid cycle, with the exception of the amount transported to the deep central part of the bay, where it would slowly decompose under nearly anaerobic conditions. It would be possible to place additional algae plantations in the bay, which could absorb up to 49 500 tons of C annually, while supplying up to 132 000 tons of О2. The obtained model estimates could be a starting point for determining the “baseline” of the content of dissolved oxygen and compiling balance equations for gas flows in the ocean-atmosphere system in the Aniva Bay before the development of seaweed plantations, which simultaneously act as carbon farms.

Влияние опасных гидрометеорологических явлений на эксплуатацию транспортного перехода через Керченский пролив

The article considers the natural and climatic conditions of the Kerch Strait, the Taman Peninsula and the Kerch Peninsula through which passes the transport crossing that connects the Republic of Crimea with the Russian mainland. The paper reflects the main features of the formation of dangerous hydrometeorological phenomena in the Kerch Strait. Hydrometeorological conditions of formation of ice and wind-wave regimes and other dangerous hydrological and hydrometeorological phenomena in the Kerch Strait are highlighted based on the coastal and expedition observations, measurements of currents at automatic buoy stations, numerical modeling of water dynamics in the Kerch Strait for different types of atmospheric effects on the grid with high spatial resolution. The research shows that in the coastal zone and on the Kerch Strait water area periodically there are dangerous hydrometeorological phenomena, such as ice blockages on the bridge piers, strong storm or hurricane wind, heavy precipitation, fogs, which significantly worsen the visibility and complicate marine cargo transportation in the Strait, thunderstorms and tornados. The data presented in this work may be the basis for the assessment of the current state of the environment within the environmental support of the projects, as well as the subsequent ice and hydrometeorological monitoring in the area of the Crimean bridge.

Identifikasi Biologi Gurita dan Nilai Indeks Untuk Pengelolaan Perikanan di Kawasan Selat Alas Nusa Tenggara Barat

Octopus is an important economic fishery commodity that has a high price and is a source of foreign exchange for the country, especially for fishermen in the West Nusa Tenggara region. The utilization status of the octopus fishery is not known yet and managed well for its purposes. This research aims to determine existing conditions, growth patterns, body shape, age group and condition factors, as well as to determine the index value and desired status of the biological dimensions of octopus fisheries management. The method used in this research is descriptive, where data is obtained from samples obtained from nature. The research results showed that the growth pattern of octopus caught in the waters of Alas Strait and landed on Ketapang beach, East Lombok Regency was negative allometric with a b value of 1.4516. Meanwhile, the octopus's body shape is in the less flat category with a condition factor (K) value of 1.91, with a length range between 25 cm - 60 cm. The status of stopping octopus management from the biological dimension obtained a value of 58.53% with quite sustainable status.

Water sources of the Lombok, Ombai and Timor outflows of the Indonesian throughflow

The Lombok Strait (LS), Ombai Strait (OS), and Timor Passage (TP) are three major outlets of the Indonesian Throughflow to the Indian Ocean. Here, sources and pathways of the LS, OS, and TP outflows are explored by a Lagrangian particle tracking analysis based on a ~3 km regional ocean model simulation. The Makassar Strait transport contributes to ~80%, ~75%, and ~45% of the LS, OS, and TP outflows, respectively. However, ~41% and ~19% of the TP and OS outflows stem from the Lifamatola Passage, which largely feeds the upper and intermediate layers of the outflows. The role of Karimata Strait is quite limited and restricted to the upper layer. It takes 1-2 years and 2-6 years for the Makassar Strait water to reach the OS and TP, respectively, whereas the Lifamatola Passage water passes through the OS (2-6 years) and TP (3-9 years) on a prolonged transit time. In the Banda Sea, the western boundary current is the main pathway toward the OS, while the waters to the TP tend to take a basin interior route.

Some biological aspects of indian mackerel (Rastelliger kanagurta Cuvier, 1817) in Bali Strait waters

Indian mackerel (Rastrelliger kanagurta Cuvier, 1817) is a small pelagic fish species which is the main catch commodity in purse seine and jukung fleets in the Bali Strait waters. Sustainable management is urgently needed for indian mackerel populations in Bali Strait waters to remain sustainable fishery. The availability of basic information such as biological aspects is very important as a fundamental resource in the management of indian mackerel in Bali Strait waters. The aims of this study were to reveal several biological aspects of mackerel such as growth patterns, condition factors, sex ratio, and size at first maturity of indian mackerel in Bali Strait waters. Sampling was carried out in May-September 2018. Samples of fish were taken from purse seine and jukung fleets using trawl nets and gill nets. Fish sample was measured, weighed and dissected to observe the sex and the gonadal maturity stage. The total number of indian mackerel samples was 167 individuals. Mackerel in the Bali Strait waters has a positive allometric growth pattern with fish in good condition. The sex ratio was in an unbalanced condition with the number of male fish being more than the female fish. The size at first maturity was 19.34 cm for male fish and 19.76 cm for female fish.

Shadow zone mapping using parabolic equation method in the Bali Strait Waters

Shadow Zone is an area where sound waves cannot penetrate a water column due to deflection. This study aims to map the shadow zone based on oceanographic parameters in the Bali Strait. The data used are temperature, salinity, and depth for 31 days in the East Season (July) in the Bali Strait at two stations from the results of numerical modeling downloaded from the website https://marine.copernicus.eu/. Shadow zone simulation uses the parabolic equation method with certain parameter limits. The vertical temperature profile shows that the deeper the water is, the lower the temperature, whereas salinity is the opposite. The sound velocity is affected by the parameters of temperature and salinity. At the location of the 25 m transducers, the undetected medium beam is narrower than the location of the 110 m transducers so that the shadow zone with a 110 m transducer position has a broader area. The Shadow zone area in the northern Bali Strait is effectively detected using a frequency of 100 Hz. In comparison, in the southern part of the Bali Strait, it is effectively seen at a frequency of 38 Hz, with the respective transducer positions used at a depth of 25 and 110 m.

Selektivitas Pancing Terhadap Hasil Tangkapan Ikan Selar (Selar crumenopthalmus) di Perairan Selat Seram

Gear selectivity is an important part of controlling the size of fish that are suitable for catching so that fish resources are maintained. The size of the hook is one of the factors that affect the selectivity of the fishing line. The purpose of this study is to analyze the selectivity of fishing lines on the results of catching Selar crumenopthalmus. Fish sampling was carried out by following a series of fishing operations by fishermen using hook sizes no. 17 and 18. The Holt method was used to analyze and calculate the selectivity of hook size operated by fishermen on the total length of the fish line. Size distribution of the total length of hook no. 17 in the middle-class size 16.5 cm – 22.5 cm and hook no. 18 in the middle-size class 16.5 cm – 20.5 cm. The distribution of length sizes on both hooks tends to be normally distributed and the proportion of large lengths is higher on hook no. 17. The 50% and optimal (100%) chance of being caught for hook size no. 17 is 18.3 and 20.1 cm, respectively. while the size of hook no. 18 is 167 cm and 18 cm. It is recommended to use hook size for trevally resources in the Seram Strait waters is hook no. 17.

Fishery-based adaption to climate change: the case of migratory species flathead grey mullet (Mugil cephalus L.) in Taiwan Strait, Northwestern Pacific.

The flathead gray mullet (Mugil cephalus L.) is a cosmopolitan fish that lives in warm and temperate zones over 42°N-42°S. It is a key fish species for industrial fishing off coastal Taiwan. Gray mullets enter the coastal waters of the southeastern Taiwan Strait (22°N-25°N) to spawn in winter and feed in the coastal and tidal waters of China (25°N-30°N). From 1986 to 2010, the annual catch of gray mullet decreased substantially and remained low. Although the Pacific Decadal Oscillation and El Niño-Southern Oscillation are recognized to affect gray mullet migration, the increase in sea surface temperature may be the main cause of the aforementioned decrease. We explored how weather changes affect fishing conditions and patterns at the gray mullet fishing grounds in Taiwan's coastal areas. Because of the decrease in gray mullet catches, the most common method for catching gray mullet in Taiwan's coastal areas between 1990 and 2010 was the use of drift or trawl nets instead of two-boat purse-seiner fleets. Since 2012, purse-seiner fleets have become the most common method for catching gray mullet. This trend indicates that the local fishing industry is adapting to changing environmental conditions.

Features of pink salmon Oncorhynchus gorbuscha (Salmonidae) fishery on the Sakhalin coast of the Tatar strait

Pink salmon is a traditional object of fishing in Sakhalin coastal waters of the Tatar strait, where it was caught for a long time off the southern part of the coast. In the last 20 years, there has been a shift in timing of pink salmon approach to the area of trap-nets a later date, as well as the main fishing sites shifting from the southern to the central areas of the coast. During these years, water cooling has observed in May, which could cause a delay in fish migration to the Tatar Strait. Also, in June and July in the northern regions, due to rapid warming, the water temperature became the same as in the southern regions of the strait. It’s known that such thermal regime changes largely determined by the intensity of penetration of the Tsushima current waters into the Tatar Strait, which apparently caused the shift of pink salmon accumulations in the strait to the north.

Diet analyses of the pelagic thresher shark, Alopias pelagicus (Lamniformes: Alopiidae), from the Lombok Strait waters, Indonesia

Abstract. Alghozali FA, Salsabila R, Gustianto MWD, Putri HMIH, Himawan MR, Yuneni RR, Hatmoro CK, Rezkiani M. 2023. Diet analyses of the pelagic thresher shark, Alopias pelagicus (Lamniformes: Alopiidae), from the Lombok Strait waters, Indonesia. Biodiversitas 24: 3708-3714. The pelagic thresher shark, Alopias pelagicus, is an endangered shark species estimated to be declining in the Pacific and Indian Oceans because of overexploitation, including from target fisheries and bycatch. Despite its importance in providing better information for species management, the ecological aspects of this species are still rarely studied. This study aims to provide information on the feeding ecology of the pelagic thresher sharks from the Lombok Strait. Stomach samples from 178 specimens were sampled from 2020-2021, and 149 stomachs that contained food contents were analyzed for species diet characterization. Prey Species Accumulation Curve slope values are &lt;0.1 and the percentage of prey coverage for all sharks combined is 92.1%, suggesting reliable inventory in the number of prey represented. The resulting diet indexes suggest that A. pelagicus in Lombok Strait waters is a specialist predator (Ba=0.3) with few prey variations (H=2.21) and no competition between sexes and maturity stages of the species (C=0.64 and 0.81, respectively). The top three prey species found for A. pelagicus in the study area are the Auxis thazard (85.8 %IRI), Sthenoteuthis oualaniensis (8.5 %IRI), and Dasyscopelus spinosus (1.11 %IRI). A better understanding of the overlap of A. pelagicus and its diet, which includes economic fish commodities, will inform authorities to develop better fisheries and conservation management for the species in Indonesia.

Analysis of fresh seawater fish production value for 2016 – 2020 in Bima District

Fisheries are among the leading resources in the Bima District area. This is because of aquaculture and capture fisheries. This condition is caused by the Bima district area being surrounded by the Indian Ocean, Flores Sea, and Sape Strait waters. Therefore, this study aimed to determine the production value of fresh seawater fish in the Bima district area and the SLS value. Observations were made by analyzing data on wet sea fish production value in each sub-district during 2016 – 2020. Data were obtained from the Bima Regency Maritime Affairs and Fisheries Service. From the observation results, it was found that the water fish production value was obtained in the Sape Sub District at 231957.21 tons and the lowest was in the Parado Sub-District which was 55694.1 tons. Meanwhile, if the sales value of fresh seawater fish, only Sape Sub-District has a sales value of IDR 1,033,373,551,615 and at the same time is the highest value compared to other sub-districts with sales values below IDR 200,000,000.

The Catch of Little Tuna (Euthynnus sp.) in Relation to Thermal Front in the Makassar Strait

The Makassar Strait waters area is a potential area for the utilization of marine fishery resources in Indonesia especially for large pelagic fisheries because it is one of the migration trajectories of little tuna (Euthynnus sp.). In order to optimally utilize tuna resources, remote sensing technology based on oceanographic satellite imagery can be relied upon to facilitate identification, prediction, and spatial and temporal mapping of potential fishing areas. This study aims to study the phenomenon of oceanography (thermal front) as an indicator of potential for little tuna fishing areas in the Makassar Strait. Primary data was obtained through in-situ data collection (direct observation in the field by following fishing operations using the purse seine, while secondary data consisting of oceanographic data such as sea surface temperature and sea surface chlorophyll-a concentrations sourced from satellite imagery data (Aqua satellite with MODIS sensor). The distribution of the thermal front was analyzed using ArcGIS 10.4 software to determine the relationship between little tuna fishing productivity and the oceanographic phenomenon. Based on the analysis results, total of 61 positions for little tuna fishing using a purse seine, five (5) fishing positions were in the thermal front area, where the catch of little tuna is higher than the average catch outside the area. These results indicate that the thermal front can be used as an indicator of potential for little tuna fishing areas in the Makassar Strait.