Waters Off Research Articles

Regional range extension of two xanthid crab species (Decapoda, Brachyura) to the mid-Sanriku Coast, the coldest waters off Honshu, Japan

Abstract This paper reports the first occurrences of two brachyuran crab species of the family Xanthidae MacLeay, 1838, viz., Actaea semblatae Guinot, 1976 and Gaillardiellus orientalis (Odhner, 1925), from the mid-Sanriku Coast, along the Pacific coast of northeastern Japan. While these records do not represent the northern limit of distribution of these species, they do show a range extension into the coldest waters of Honshu, the main island of Japan, probably due to global warming and changes in flow patterns of the local sea currents.

A Study on the Rational Decision-Making Process of Vessel Organization—Focusing on Cases of Vessel Accidents

Vessel organizations are exposed to the risk of accidents due to the limited experience and intuition of the top decision makers in the organization in the special environment of the sea. This study aims to provide a direction for sustainable and rational decision-making in vessel organization through decision making process theory and case studies of actual vessel accidents. The results obtained from the actual case studies show that all three vessel accidents were caused by the arbitrary decision of the decision maker based on the Garbage Can model. This can be attributed to the closed nature of the vessel’s organization, which requires a decision-making process that is a hybrid of the Carnegie Decision model and Management Science model. Implications include the introduction of a ‘My Ship’ system, the de-subjectivization of top decision makers, situational awareness, and the need to provide top decision makers with the context and information relevant to their decisions. Limitations of this study include the fact that the case study was conducted only on Korean-flagged vessels and the study was limited to vessel accidents that occurred in the waters off Korea, China, and Japan, which limits the generalizability of the findings. In order to overcome these limitations, it would be interesting to conduct a follow-up study to include vessel accidents of different nationalities or to further investigate the characteristics of the decision-making process in vessel accidents by country.

Distribution and Some Aspects of Biology of Lycodes brunneofasciatus (Zoarcidae) in the Sea of Okhotsk Waters off Kamchatka in Autumn 2012 and Summer 2016

Distribution and Some Aspects of Biology of Lycodes brunneofasciatus (Zoarcidae) in the Sea of Okhotsk Waters off Kamchatka in Autumn 2012 and Summer 2016

Shylock in Fuquieo: Shakespeare’s The Merchant of Venice and the Trial of a Portuguese Stranger by China’s Courts in Richard Hakluyt’s Principal Navigations

In 1548, the Portuguese merchant Galeotto Perera was captured along with his shipmates in the waters off China’s southeastern coast. In his account of his time as a prisoner in Fuquieo (in contemporary Fujian province), Perera details his trial before the city’s magistrates in a Chinese court of law, writing of his amazement when he and his fellow Portuguese merchants were acquitted of the charges brought against them by two of the city’s most prominent men. Perera’s prison account reached an Elizabethan readership via Richard Hakluyt’s Principal Navigations (1589), a sprawling compendium of European travel writing translated into English. In this essay, I maintain that the outcome of Shylock’s trial in Shakespeare’s comedy entails a reversal of Perera’s legal fortunes in China. In light of Perera’s assertion that the Chinese legal process “cannot be falsified, as it happeneth sometimes with vs,” I argue that The Merchant of Venice asks why these European failures of justice, mercy, and truth sometimes happen in Europe’s courts and in negotiations with non-Christian peoples. I aim to demonstrate that the comedy’s treatment of economic and religious exchange with strangers is inflected by Perera’s account of his encounters with the Chinese during his time in Fuquieo—as well as by other travel writings collected by Hakluyt that describe legal, financial, and inheritance quandaries that European traders faced during their travels to places like China, Java, and modern-day Myanmar.

The Ecological Niches and Interspecific Associations of the Dominant Fishes in the Xiamen Seas, China

Fish are vital in enhancing the stability of marine ecosystems. Therefore, understanding the ecological niches and interspecific correlation characteristics of their dominant species provides a good scientific basis for the protection and management of marine biodiversity. In this study, on the basis of survey data from trawls conducted in the waters off Xiamen in the spring (April) and autumn (November) of 2021, the ecotopes and interspecies connectivity of the dominant fish species were investigated using the relative importance index (IRI), χ2 tests, the association coefficient (AC), and Pearson and Spearman analyses. According to the IRI, there were 23 fish species with higher values, including 15 species in spring and 15 species in autumn. The 15 dominant fish species could be subdivided into wide-, medium-, and narrow-ecotope species, of which there were 2 and 3 wide-ecotope types in spring and autumn. The niche overlap indices exhibited a range of 0.000–0.809 in the spring and 0.000–0.915 in the autumn, showing small differences between the two seasons. The interspecific correlations between the dominant fishes in Xiamen’s waters in spring and autumn were weak, and both showed non-significant positive correlations, indicating that the correlations between the dominant fishes in this sea area are relatively independent. The findings of this investigation provide a fundamental database and theoretical framework for researching the adaptive mechanisms of marine fish in the Xiamen Seas.

Otolith elemental composition indicates differences in the habitat use for larvae and early juveniles of Japanese jack mackerel (Trachurus japonicus) in the waters around Japan

AbstractTrace element analysis of otoliths from core to edge was used to reveal differences in habitats of larvae and early juveniles of Japanese jack mackerel (Trachurus japonicus) caught in the East China Sea (ECS), Pacific Ocean, and Sea of Japan. Multi‐element signatures (Sr:Ca, Mg:Ca, Na:Ca, K:Ca, and Ba:Ca) were analyzed with multivariate statistics to determine whether these element signatures provide insight into regional population structure. The median values of elements: Ca ratios in otolith core region differed significantly among areas, with most elements between the ECS and the Pacific Ocean or Sea of Japan showing significant differences. The Sr:Ca ratios exhibited a V‐shaped trend from the otolith core to the edge, which was likely related to the vertical habitat layer shift of larvae and early juveniles of T. japonicus. Canonical analysis of principal coordinates using the element: Ca ratios and the hatching day were re‐classified according to the sampling area with higher accuracy in the ECS (88–95%) and the Sea of Japan (76–83%) compared to the Pacific Ocean (69–72%). These results indicate that the proportion of eggs, larvae, and early juveniles transported by the Kuroshio Current from the southern ECS—the main spawning ground—to the Pacific Ocean or the Sea of Japan is low and that juveniles distributed in the coastal waters off southwestern Japan may have originated from local spawners. These results suggest that determining the elemental composition of larvae and juveniles of T. japonicus is effective in determining the habitat differences of this species in the three regions. These findings will help to understand population structure and recruitment process of this species around Japan.

Generation and complexity analysis of ship encounter scenarios using AIS data for collision avoidance algorithm testing

Collision avoidance algorithms are critical for enhancing ship navigation safety. To ensure the reliability of these algorithms, comprehensive testing is imperative prior to their deployment. A pivotal aspect of such testing is the strategic formulation of testing scenarios, which plays a vital role in securing the trust of testing phase results. This study proposes a systematic method for generating ship encounter scenarios and analyzing their complexity using Automatic Identification System (AIS) data, to support the implementation of collision avoidance algorithm testing. Firstly, real-world ship encounter scenarios are extracted from AIS data by considering the spatial and temporal dependencies among ships. Subsequently, a complexity evaluation model based on encounter topology evolution is designed to assess the complexity of these scenarios. Finally, detailed strategies for using these scenarios in collision avoidance algorithm testing are explored based on the complexity evaluation results. Real AIS data from the waters off Ningbo-Zhoushan Port is collected to validate the performance of the proposed method. Research findings indicate that the proposed method successfully separates numerous ship encounter scenarios from historical AIS data and comprehensively evaluates their complexity. Based on this foundation, valuable guidance is provided for the application of extracted scenarios in collision avoidance algorithm testing.

Spatial Patterns and Evolution Features of Marine Cold Spells in the Arabian Sea during the Past Three Decades

Marine Cold Spell (MCS) events are cold sea states with potentially devastating impacts on marine environments and ecosystems. In this study, we analyzed different MCS types with various severe categories in the Arabian Sea during 1994–2023. We found that all four types of MCS events shared a similar spatial pattern in terms of frequency, mean duration, mean intensity, and total days, but the frequency of 1-MCS events had a sharply decreasing trend compared with any other type of MCS events, indicating that ocean warming mainly led to the significant disappearance of short-period MCS events. Moreover, the MCS events in offshore Somalia had the highest occurring frequency, longest duration, largest intensity, and maximal total days, and were significantly different from those in other regions of the Arabian Sea. This is originated from that the cold–warm changes of the Somali current make larger fluctuations in the sea surface temperatures of the waters off Somalia, enhancing the occurring probability of MCS events, especially during the summers.

The Effect of Wind Speed and Sea Surface Temperature on Chlorophyll –A Concentration in Sea Water Off the Libyan Coast

The effect of winds and sea surface temperature on the concentration of chlorophyll-a, which is the primary source for phytoplankton to produce carbon through photosynthesis, is one of the climatic changes formed in the atmosphere and oceans that are the focus of current global studies. The study found a strong correlation between the concentration of chlorophyll-a and wind speed. The concentration of chlorophyll-a rises with increasing wind speed and reaches 0.85. Conversely, the relationship between sea surface temperatures and chlorophyll-a concentration is inverse, meaning that the higher the sea surface temperatures, the lower the concentration of chlorophyll-a. The inverse relationship approaches -0.798 in seawater. The intensity of chlorophyll-a concentration at sea and its relationship with wind speed and sea surface temperature explain why the percentage of the effect of variable wind speed and sea surface temperature on the concentration of chlorophyll-a is affected by (73.6%, 63.8%) on the concentration of chlorophyll-a, respectively.

Status of the transfer state of 137Cs in zooplankton and surface water fish off Fukushima during 2018–2021

Radiocaesium introduced to coastal waters by the accident at the Fukushima Dai-ichi Nuclear Power Station (F1NPS) elevated the radioactivity level in biota. The radionuclide level in zooplankton, concentration of 137Cs radioactivity in surface water fish decreased rapidly, which was the primary food source for planktivorous fish, was recognized as not to be depurated at the same level prior to the accident. To evaluate the possible cause of this phenomenon, zooplankton and surface water fish were collected off Fukushima during 2018–2021, and the presence of radioactive particles was also examined. The concentrations of stable Cs and 137Cs radioactivity were analysed along with aluminium which was an indicator element of Cs that originated from suspended particles which were attached to or ingested by zooplankton. As a result, radioactive particles were often found in coastal zooplankton samples, and stable Cs and 137Cs of this inorganic fraction were identified. After removal of this excess radioactivity, the 137Cs radioactivity in whole-body tissue of zooplankton was derived. However, the level in the soft part of zooplankton during 2018–2020 was still greater than the levels which existed before 2010. Since habitat seawater was understood to not be a substantial source of 137Cs, then 137Cs transfer along the food chain, possibly from phytoplankton or detritus of enhanced radioactivity were suggested as important sources of 137Cs. In addition, enhanced 137Cs radioactivity in zooplankton was considered consequently elevate radioactivity levels in surface-dwelling water fish off Fukushima. Although the radioactivity level was not radiologically significant in relation to seafood safety limit, enhanced 137Cs radioactivity levels in biota was demonstrated in southern waters off Fukushima. In contrast, derived 137Cs/133Cs atom ratios of fish and seawater south of 37°E and west from 142°E indicated that radiocaesium transfer between fish and the environment was in an equilibrium state, showing the environment beyond these geographical coordinates had returned to the pre-accident state.

Taxonomy and fatty acid profile of Picochlorum geojense sp. nov. (Chlorophyta, Trebouxiophyceae) from Korean coastal waters

ABSTRACT The microalgal genus known as Picochlorum, belonging to the green algae family Trebouxiophyceae, is recognized for its rapid growth and high lipid productivity. A Picochlorum strain (GJ210610) was recently established from the waters off Geoje, South Sea of Korea. Picochlorum sp. GJ210610 was a single, green ellipsoidal cell with an average size ranging from 1 to 2 µm. Its reproduction occurred through autosporulation. A phylogenetic tree based on nuclear small-subunit rDNA sequences revealed that this strain formed a unique branch, distinct from other Picochlorum species. Furthermore, the secondary structure of the ITS2 sequences was revealed for the first time within Picochlorum. The newly discovered Picochlorum sp. grew between 15°C and 25°C, with survival ceasing at 30°C. The maximum specific growth rate was measured at 0.91 d−1 at 25°C. The fatty acids of Picochlorum sp. GJ210610 were palmitic acid, oleic acid, linoleic acid, and alpha-linolenic acid. Based on morphological and phylogenetic analyses, we propose Picochlorum geojense sp. nov. (GJ210610) as a new species. The results of the present study may enhance our knowledge of the taxonomy and ecological characteristics of Picochlorum.

Assessing vessel transportation delays affected by tropical cyclones using AIS data and a bayesian network: A case study of veronica in northwestern Australia

Tropical cyclones frequently disrupt maritime transportation systems, impacting the normal operation of vessels and causing transportation delays. Analyzing the occurrence and degree of vessel transportation delays under disaster conditions is one of the critical aspects of maritime transportation management. This article, based on Automatic Identification System (AIS) data, examined the real behavioral trajectories of vessels and delay characteristics during tropical cyclones. Taking the example of Tropical Cyclone Veronica, which occurred in the waters off northwestern Australia in 2019, we conducted a comprehensive analysis. This involved numerical simulations of the entire disaster process and the cleaning and matching of trajectory data for all affected vessels in the area. We delved deeply into the relationship between vessel behavior characteristics and tropical cyclones, identified factors contributing to delays, and, based on our findings, constructed a Bayesian network inference model for vessel transportation delays under disaster conditions. This model uses information such as tropical cyclone intensity, vessel basic attributes, behavior choices, and port disaster avoidance measures as its primary nodes. The research results indicate that vessel rerouting, vessel loss of control, and waiting for port entry are the three major sources of vessel delays during disasters. Key influencing factors contributing to these consequences include port closure measures, the duration of vessels being adversely affected by strong winds, vessel tendencies toward loss of control, and risk preferences. To control the extent of vessel delays more effectively, it is crucial to prioritize these sensitive factors and strengthen monitoring and management efforts. This model is driven by real data, providing an objective reflection of real-world scenarios, and its effectiveness has been validated through sensitivity analysis. The research perspective and algorithmic framework presented in this paper offer a novel paradigm and fresh perspective for the study of maritime transportation disasters. The research findings have significant implications for bolstering the resilience of maritime transportation networks, enhancing our comprehension and anticipation of delays, and ensuring the continuity, security, and efficiency of the global supply chain for goods.

Site Selection for Offshore Wind Power Farms with Natural Disaster Risk Assessment: A Case Study of the Waters off Taiwan’s West Coast

This research examines the risk of natural disasters for offshore wind turbines together with their potential wind energy capacity to help the site selection of offshore wind power farms. Through evaluations of expert questionnaires, we use the fuzzy analytic hierarchy process to weight how natural disasters damage the sub-assemblies of an offshore wind turbine, then obtain the natural disaster risk assessment model, and finally utilize ArcGIS Pro 3.2 to map the potential wind farm sites for the waters off Taiwan’s west coast. We identify that typhoons are the most threatening type of disaster to generators, rotor blades, and rotor hubs; earthquakes are the most threatening to towers; and lightning is the most threatening to transformers. For the whole wind turbine, wind is ironically the most threatening natural disaster, followed by lightning, sea waves, and then earthquakes. Lastly, we examine the results by overlapping the offshore wind farms developed and planned in Taiwan, which coincide with locations in relatively low risk and high wind speed areas.

Distribution and Some Aspects of Biology of Lycodes brunneofasciatus (Zoarcidae) in the Sea of Okhotsk Waters off Kamchatka in Autumn 2012 and Summer 2016

Distribution and Some Aspects of Biology of Lycodes brunneofasciatus (Zoarcidae) in the Sea of Okhotsk Waters off Kamchatka in Autumn 2012 and Summer 2016

Landings of Sphyrna zygaena (Linnaeus, 1758) in northern Peru indicate a lack of adult specimens

A commercial fishery for the smooth hammerhead shark (Sphyrna zygaena) exists in the waters off northern Peru. Although international and domestic norms regulate this species, adult specimens are becoming rare. Monthly visits to four ports in the La Libertad region were made to measure S. zygaena landings and understand the present state of the fishery. We found that 92% of the specimens landed were juveniles or younger and that 10% of the original biomass remains in the fishery. This highlights that stricter regulations such as protecting breeding areas, establishing a legal catch length, and limiting the catch volume and fishing season are urgently needed to maintain a sustainable fishery.

Seasonal Variability of Sea Surface Chlorophyll-a at West Borneo Island

The optimization of marine fisheries activities can be achieved through an understanding of the timing of fishing, access to good information, and knowledge of oceanographic conditions. These conditions often lead to significant nutrient enrichment in the surface layer of the ocean, which in turn increases the sea surface chlorophyll-a (SSC). In the context of the west Borneo Island region, seasonal variability in SSC plays a crucial role in determining potential fishing grounds. The objectives of this study are examining the seasonal variability of SSC, identifying upwelling and downwelling processes through analysis of sea surface wind (SSW), and determining the climatological distribution of Sea Surface Temperature (SST) and sea surface height (SSH) within the water off Labuan Island, Malaysian Borneo, and the Karimata Strait, West Kalimantan, Indonesia. Remote sensing data spanning from 2007 to 2021 were analyzed, encompassing SSC, SST, SSH anomalies, SSW, wind stress curl, and Ekman pumping. Additionally, rainfall and river discharge were examined as supplementary indicators of these oceanographic processes. The findings indicate that SSW plays a pivotal role in driving upwelling and downwelling processes, which in turn influence SSC variability. In Labuan waters, upwelling occurs primarily from November to February, while downwelling predominates from June to September. In contrast, in the Karimata Strait, upwelling is identified from July to September, with downwelling prevalent between March and May. Upwelling events in both regions are characterized by increasing SSC, accompanied by decreasing SST and SSH, while the opposite trends are observed during downwelling events. The peak of rainfall and river discharge in December is noted to potentially enhance SSC variability in the Karimata Strait compared to Labuan Island waters.

Renewed occurrence of schooling scalloped hammerhead (Sphyrna lewini) and of great hammerhead (S. mokarran) sharks in the Cayman Islands

The scalloped hammerhead shark (Sphyrna lewini), a critically endangered species with a decreasing global population, is characterised by its occurrence in large schools. Such schools are still observed today in the Pacific Ocean, but this is generally not the case in the Atlantic Ocean, and in the Cayman Islands not since the 1970s. Here we report a recent record of a school of S. lewini in deep water off Grand Cayman, and describe a recent, concomitant increase in numbers of the species, and its critically endangered congener, the great hammerhead (Sphyrna mokarran), around the Cayman Islands. Relative population trends and seasonal patterns were assessed using data from shallow and deep-water BRUVS, scientific longlining, citizen science projects including the Sharklogger Network and REEF, and social media reports. It appears that S. lewini may be slowly re-occupying the area, selecting and using deeper waters to school, while S. mokarran has also become less scarce than hitherto.

Ⅰ–2. Catch and biological characteristics of spear squid (<i>Heterololigo bleekeri</i>) in the coastal water off Miyagi Prefecture

Ⅰ–2. Catch and biological characteristics of spear squid (<i>Heterololigo bleekeri</i>) in the coastal water off Miyagi Prefecture

Photo-Identification and Skin Lesion Prevalence of Bottlenose Dolphins (Tursiops erebennus) in the Waters of New York and New Jersey

Cetaceans can serve as sentinel species in marine environments as long-lived, apex predators that can concentrate environmental contaminants with potential health consequences. Thus, monitoring the well-being of these species may provide an additional indicator of ecosystem health. In cetaceans, one method for assessing individual and population health is by examining skin conditions. For decades, skin lesions have been increasingly documented in coastal populations of bottlenose dolphins (Tursiops spp.) worldwide. Lesion presence can indicate diminished health and may reflect environmental stressors. Herein, we document the prevalence of epidermal lesions/marks in bottlenose dolphins from the waters off New York and New Jersey during their seasonal presence from spring to fall. Photographs of distinct individuals sighted from May to October 2017 to 2021 were compiled into a catalog, and skin lesions were categorized and counted. Annually, the lowest skin lesion prevalence was in 2021 (p = 0.31), and the highest was in 2017 (p = 0.81). By month, prevalence generally decreased from spring to fall. Overall lesion prevalence in this population was higher than reported estimates for other populations in the coastal waters of the United States. The five most common categories were cloudy white spots, dark spots, white amorphous lesions, tattoo lesions, and dark fringe lesions; and the three most common groups were potentially pathogenic lesions, hypopigmentation, and rake mark-associated potentially pathogenic lesions. Some of the observed lesions have been associated with viral infections that may be exacerbated by environmental stressors. This research establishes an important baseline for further studies into bottlenose dolphin population health in and around the New York–New Jersey Harbor Estuary, particularly given the continued expansion of anthropogenic activities, including those related to forthcoming offshore wind development.

An assessment of demersal fisheries by trawling in less than 50 m of water off Egypt’s Mediterranean coast

Trawl fishing is identified as one of the most significant factors that could affect the diversity of demersal fish groups but not for all depth strata. Since the increased exploitation of Non-Indigenous Species (NIS) has caused the trawl fishing grounds to shift towards shallower seas where their biomass density is maximum, this study aimed to assess demersal fisheries by bottom trawls in the Mediterranean water off Egypt at depths less than 50 m. In this study, data from eight bottom-trawl hauls were used to describe the diversity of the demersal fish catch. The hauls varied in their species composition and both in the number and the weight of individuals. The length frequency distribution of the most occurred species was studied. A total of 87 species were identified in the catch, out of which 32 were recognized as NIS. The percentages of most of the NIS decreased from the east to the west of the surveyed area. There are always changes in fish diversity because of increasing fishing efforts on demersal fish communities, but not for all depth strata, therefore, a monitoring program has to be designed for better assessment of fisheries resources in the Mediterranean water off Egypt.