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Length-Based Stock Assessment of Scomberoides commersonnianus (Talang queenfish) from Gwadar Coast, Balochistan, Pakistan
No full textThis study represents the first comprehensive assessment of Scomberoides commersonnianus stock status along the Gwadar coast using a length-based stock assessment approach. The analysis was conducted using the TropFishR package to estimate key growth and mortality parameters, exploitation rates, and biological reference points through yield-per-recruit modeling. The length–weight relationship revealed an isometric growth pattern for Scomberoides commersonnianus (b = 3.0; R² = 0.96). Growth parameter estimates yielded an asymptotic length (L∞) of 104.31 cm and a growth coefficient (K) of 0.35 year⁻¹. Mortality assessments indicated a total mortality rate (Z) of 1.56 year⁻¹, natural mortality (M) of 0.41 year⁻¹, and fishing mortality (F) of 1.15 year⁻¹, resulting in an exploitation rate (E) of 0.73 well above sustainable levels and indicative of excessive fishing pressure. These results highlight that Scomberoides commersonnianus along the Gwadar coast is experiencing unsustainable exploitation. Management actions are required to reduce fishing pressure by approximately 36.5% to facilitate stock recovery and ensure the long-term sustainability of this valuable coastal fishery.11Nsciescopu
Effect of the harmful microalga Heterosigma akashiwo on aggregation and sinking of microplastics
No full textThe exponential increase in plastic production, coupled with the growing influx of microplastics (MPs) into the ocean, raises questions about the environmental impact and ultimate destination of these MPs. Aggregation processes of microalgae have significant effects on the vertical distribution of MPs in the marine environment. This study explored how the harmful microalga Heterosigma akashiwo affects the aggregation and sinking characteristics of four types of MPs: low and high-density polyethylene (PE) spheres, and small and large polypropylene (PP) fragments. The aggregation of MPs was primarily driven by extracellular polymeric substances (EPS) rather than direct attachment to the cells, contributing to their sinking. The sinking of low-density PE spheres followed a logistic function, saturating at 28% with a half-saturation time of 9 days. In contrast, small PP fragments sank minimally (under 2%) and large PP fragments showed almost no sinking, indicating the varying impacts of MP density and size. The sinking velocity of the MP aggregates was significantly lower for low-density PE spheres (0.63 mm·s⁻¹) than for high-density PE spheres (0.81 mm·s⁻¹), despite no significant differences in aggregate size or MP particle number. This result may suggest that low-density MPs could potentially affect marine carbon cycle. Furthermore, no clear evidence was found for the resuspension of the settled aggregates due to bacterial decomposition under dark and cold conditions. As the first experimental study to explore the aggregation, sinking, and resuspension of different MPs in the presence of H. akashiwo, these findings, when integrated with field observations and modeling studies, provide valuable insights for predicting MP distribution in marine environments.1
Seawater Acidification-Responsive Genes in Female Gametes of Undaria pinnatifida
No full textThe brown alga Undaria pinnatifida is an important marine food source in Northeast Asian countries, including China, Japan, and Korea. However, its natural populations are increasingly affected by global climate change. Among the various environmental stressors, ocean acidification and warming are major concerns for marine ecosystems. In this study, we investigated the transcriptional response of U. pinnatifida female gametes to acidified seawater conditions using RNA sequencing and Gene Ontology (GO) analyses. Female gametes were exposed to acidified conditions (pH 7.8) for 1 and 3 days. After 1 day of exposure, enriched GO terms included chromatin organization (GO:0006325), chlorophyll biosynthetic process (GO:0015995), photosynthesis (GO:0015979), cell plate formation involved in plant-type cell wall biogenesis (GO:0009920), glucose homeostasis (GO:0042593), galactose metabolic process (GO:0006012), rRNA processing (GO:0006364), fatty acid metabolic process (GO:0006631), regulation of transcription by RNA polymerase II (GO:0006357), and cellular response to DNA damage stimulus (GO:0006974). In contrast, after 3 days of exposure, different GO terms were affected, including regulation of plasma membrane sterol distribution (GO:0097036), chloroplast fission (GO:0010020), proteolysis (GO:0006508), protein targeting to chloroplast (GO:0045036), DNA repair (GO:0006281), protein metabolic process (GO:0019538), RNA processing (GO:0006396), and chromatin organization (GO:0006325). These findings suggest that ocean acidification alters key metabolic and regulatory pathways in the female gametes of U. pinnatifida, providing insight into the molecular mechanisms underlying its stress response to changing seawater chemistry.1
Cultivation strategies for scallop species in response to elevated sea temperature changes in south korea
No full textGlobal climate change has led to increasingly frequent and intense episodes of elevated sea surface tem- peratures. These temperature shifts are known to cause significant physiological stress in marine organisms, particularly through oxidative stress. Scallops, one of the most important aquaculture bivalves globally, are es- pecially popular in East Asia, where species such as Chlamys farreri (Zhikong scallop) and Argopecten irradians (bay scallop) are widely farmed due to their favorable taste and high nutritional value. As global demand for seafood continues to rise, scallop aquaculture is also expanding. However, mass mortality events of bivalves during summer have become increasingly common in regions like South Korea, primarily due to abrupt and extreme changes in sea temperature.
To address this issue, it is crucial to investigate molecular-level responses to thermal stress and to explore practical mitigation strategies in aquaculture settings. In this study, we focus on C. farreri and A. irradians, two scallop species cultured along the southern coast of Korea. Our research includes laboratory-scale exper- iments to analyze antioxidant system responses to temperature fluctuations and field-scale studies to assess how vertical distribution within the water column affects scallop resilience to high-temperature stress.
Despite genetic similarities among scallop species, our findings aim to identify those with higher thermal tol- erance—especially those less sensitive to sudden summer temperature changes. Furthermore, we seek to de- termine optimal aquaculture environments using vertical water column stratification as a tool to mitigate heat stress. Ultimately, our work provides foundational insights for developing more sustainable and resilient scallop farming practices in the face of climate-driven ocean warming.1
The spatial-temporal variation and transport of artificial radionuclides (137Cs and 239,240Pu) around Korea Seas (East Sea, Yellow Sea, Southern coastal of Korea)
No full textWe analyzed spatiotemporal variation in the artificial radionuclides 137Cs and 239,240Pu in seawater around Korea Seas (East Sea, Yellow Sea and Southern coastal of Korea) from 2018 to 2024. The 137Cs activity in surface water of the East Sea range of 0.88 - 1.97 mBq kg-1 (average: 1.33 ± 0.29 mBq kg-1, n=21). Vertically, the highest activities of 137Cs were sub-to surface later (0 - 100 m) and decreased with depths. The 239,240Pu activities range of 1.70 - 5.18 μ㏃ kg-1 (average: 3.83 ± 1.43 μ㏃ kg-1, n=11) in the surface layer. 239,240Pu activities were lower in the surface layer and also decreased with depths. This trend appears to be result from the adsorption onto particle and resultant sedimentation of Pu in the water column. The surface layer 137Cs activities in the Yellow sea and Southern coastal of Korea ranged from 0.56 - 1.96 mBq kg-1 (average: 1.42 ± 0.39 mBq kg-1, n= 10), 0.92 to 2.43 mBq kg-1 (average: 1.65 ± 0.33 mBq kg-1, n=29), respectively. In these regions, the spatial and vertical distributions of 137Cs and 239,240Pu were almost consistent. However, a substantial increase in 137Cs was observed at some stations in the southernmost part of South Sea, which seems to be due to the fluvial input of surround region. Overall, the distribution of 137Cs and 239,240Pu seems to be primarily influenced by local boundary inputs, such as freshwater from river, atmospheric deposition, sediment resuspension, and others from the surrounding Far East Asian continents. We quantified the interlinked budget balance of 137Cs between the East Sea, Yellow Sea and Southern coastal of Korea. This study suggests that advection from the open ocean is the dominant source of 137Cs in the Korean Seas and the major sinks for 137Cs in these regions are natural decay and removal via sinking flux.1
Reconstruction modeling and validation of brown croaker(Miichthys miiuy) vocalizations using wavelet-based inversion and deep learning.
No full textBiological vocalizations of fish serve as essential acoustic cues for underwater monitoring and ecological studies. However, limited high-qual-
ity recordings, especially for region-specific species like the brown croaker (Miichthys miiuy), hinder data-driven modeling in bioacoustics. This study introduces a wavelet-based synthesis framework using fk14 wavelets and Particle Swarm Optimization (PSO) to reconstruct brown croaker calls. A total of 522 single-pulse and 1157 pulse train signals were analyzed to extract key acoustic parameters such as sound pressure level (SPL0pk ) and inter-pulse interval (IPI). Sensitivity analysis using a normalized Bartlett processor identified wavelet delay and scale as the most influential parameters, guiding the generation of biologically valid signals with over 98% waveform similarity. The synthesized calls closely matched measured signals in both time and frequency domains. A ResNet-18 neural network trained on measured signals successfully distinguished between measured and modeled calls, demonstrating high classification performance and strong
similarity in latent feature space. These findings confirm the structural fidelity of the synthetic signals and demonstrate the potential of this method for data augmentation, passive acoustic monitoring, and the development of bio-inspired underwater communication systems. (Work supported by KRIT-CT-22-056.)1
Unmanned aerial vehicle for magnetic detection of metallic landmines in military applications
No full textLandmines significantly hinder the rapid movement of military forces and pose major obstacles during critical operations. Unmanned aerial vehicles (UAVs), commonly known as drones, offer several significant advantages for landmine detection. Most studies have tested drone-based systems at controlled sites and demonstrated their effectiveness in limited scenarios, with no examples of using these systems to detect landmines and relay the results to mine clearance machines (MCMs) for actual removal in real military operations. This study evaluated the use of UAVs equipped with magnetometers to detect metallic landmines in military applications. By conducting a series of controlled experiments, the research identified optimal flight conditions—2 m/s flight speed, 1 m survey interval, and 0.5 m sensor altitude—that balance accuracy and operational efficiency. The findings demonstrate that UAV-based magnetometer systems can significantly enhance mine clearance operations by providing near real-time data to MCMs. This approach offers a safer, faster, and more cost-effective alternative to traditional landmine detection methods by addressing the limitations of ground-based operations, such as high risk to human operators and inefficiency.11Nsciescopu
Crustal variations and tectonic implications across the South Yellow Sea based on active-source wide-angle seismic analyses
No full textThe South Yellow Sea and its environs are pivotal for unraveling the complexities of crustal dynamics and continental collision processes. A holistic assessment of deep structural variations from northern China to the Korean Peninsula is essential for a comprehensive and accurate determination of the tectonic affinity of the Korean Peninsula.Thus, we deployed a pioneering active-source seismic profile (Line2016) spanning the South Yellow Sea and the eastern onshore region of the Korean Peninsula, provides crucial insights into the collision dynamics between the Sino-Korean Block and the Yangtze Block. Our innovative approach, incorporating forward modeling, tomography, and finite-difference wavefield modeling, yielded a high-resolution crustal P-wave velocity model, addressing a significant knowledge gap in understanding the geological intricacies between northern China and the Korean Peninsula. The results confirmed and precisely located the West Marginal Fault of the Korean Peninsula, a significant crustalscale tectonic structure, likely representing the eastern boundary between the Yangtze Block and the Sino-Korean Block. The study advocates for classifying the Korean Peninsula as part of the Sino-Korean Block, presenting evidence for the one-part affinity hypothesis. This collision resulted in the creation of two distinct suture zones-an orogenic belt in the northern part and a significant strike-slip fault zone in the eastern part of the South Yellow Sea. The study emphasizes the pivotal role of block morphology in regulating plate convergence, providing valuable insights for understanding similar phenomena in other collision zones. (c) 2024 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.11Nsciescopu
Spatial and vertical distribution of per- and polyfluoroalkyl substances (PFASs) in the water columns of the regional seas of South Korea
No full textThis study focused on analyzing the spatial and vertical distributions of 28 per- and polyfluoroalkyl substances (PFASs), which comprised five precursors and three alternatives, in the water columns of the regional seas surrounding South Korea, such as the Yellow Sea (YS, Y1–Y10), East China Sea (ECS, EC1–EC6), South Sea (SS, S1–S5), and East Sea (ES, E1–E7). The concentrations of these PFASs detected in 204 seawater samples varied from below the limit of detection (<LOD) to 17 ng L−1 in the YS, 0.26–17 ng L−1 in the ECS, 0.08–3.4 ng L−1 in the SS, and <LOD to 1.4 ng L−1 in the ES, with perfluorooctanoic acid being identified as the most abundant compound. Principal component analysis grouped water masses and regions based on PFASs concentrations and compositions, enabling the identification of PFASs sources and their fate. PFASs are mainly derived from land and are transported via ocean currents, where their compositions tend to remain conservative. PFASs entering the YS are likely conveyed to the ES through ECS and SS, following the northward movement of the Taiwan Warm Current and Kuroshio Current. The ECS serves as a mixing zone for PFASs from various sources. This study provides valuable baseline data for understanding PFASs transport and the characteristics of water masses in the regional seas around South Korea. © 2024 Elsevier Ltd33Nscopu
Spatial-temporal big data analysis of ship avoidance patterns during typhoon approaches
No full textTyphoons pose a significant threat to maritime safety, affecting numerous ships and ports in South Korea annually. This study analyzes ship avoidance patterns during Typhoons SOULIK and KONG-REY using Automatic Identification System data. Through K-means clustering, anchorage and drifting patterns both inside and outside territorial waters are identified. A spatial-temporal analysis, utilizing minimum bounding geometry and centroid comparison, assesses the positions of ship clusters relative to the typhoon's path. The analysis recommends maintaining a minimum distance of 300 km from the typhoon's path for safe avoidance. Statistically significant differences in ship patterns under non-typhoon conditions were also identified using Kuiper's test. These findings emphasize the importance of data-driven decisions for enhancing maritime safety and developing typhoon avoidance strategies.11Nsciescopu