scholarly journals Current Dependent Dispersal Characteristics of Japanese Glass Eel around Taiwan

2022 ◽  
Vol 10 (1) ◽  
pp. 98
Author(s):  
Kuan-Mei Hsiung ◽  
Yen-Ting Lin ◽  
Yu-San Han
Keyword(s):  
Time Series ◽  
Mainland China ◽  
North Equatorial Current ◽  
Coastal Currents ◽  
The North ◽  
Southern Taiwan ◽  
Glass Eels ◽  
Central Taiwan ◽  
The Taiwan Strait ◽  
Dispersal Characteristics

Japanese eel larvae are passively transported to the East Asian Continental Shelf by the North Equatorial Current, Kuroshio and Kuroshio intrusion currents, and coastal currents. Previous studies have investigated the dispersal characteristics and pathways of Japanese glass eels. However, there are still limitations in these studies. According to long-term (2010–2020) catch data from the Fisheries Agency in Taiwan, the distribution and time series of glass eels recruitment to Taiwan are closely related to the surrounding ocean currents. Recruitment begins in eastern Taiwan via the mainstream Kuroshio and in southern Taiwan via the Taiwan Strait Warm Current. In central Taiwan, recruitment occurs from southern Taiwan, as well as from mainland China via the southern branch of the China Coast Current (CCC). The latest recruitment occurred in northern Taiwan and mainly comprised glass eels from mainland China via the northern branch of the CCC. A stronger monsoon during the La Niña phase could affect the recruitment time series in northern and eastern Taiwan. This study suggests that the recruitment directionality of glass eels is an indicator of the flow field of ocean/coastal currents and elucidates the dispersal characteristics of glass eels in the waters around Taiwan.

Eels at the Edge: Science, Status, and Conservation Concerns

2009 ◽  
Keyword(s):  
East Asia ◽  
Early Life History ◽  
Kuroshio Current ◽  
Japanese Eel ◽  
North Equatorial Current ◽  
Mariana Islands ◽  
The North ◽  
Management Plans ◽  
Equatorial Current ◽  
Glass Eels

Abstract.—The Japanese eel, Anguilla japonica, is an important food fish in East Asia, and catches of glass eels and of eels in freshwater appear to have declined dramatically in recent decades, causing increasing concern for the health of wild stocks. During that time, research efforts to understand its biology have progressed considerably. The spawning area was successfully outlined to the west of the Mariana Islands in 1991, and other research suggests that their recruitment success may be related to El Niño events, which appear to affect the transfer of leptocephali from the north equatorial current into the Kuroshio Current. Otolith microstructure and microchemistry studies have revealed various aspects of their early life history that relate to their oceanic larval migration. The discovery of sea eels that live in marine habitats without entering freshwater may change the common understanding of freshwater eel ecology and affect management plans. Most genetic studies suggest that the Japanese eel is composed of a single panmictic population throughout East Asia. Therefore, international management is needed among the countries of China, Taiwan, Korea, and Japan, where glass eels recruit from a common stock and are used extensively for aquaculture.

scholarly journals Spatial and seasonal variations of aerosols over China from two decades of multi-satellite observations – Part 2: AOD time series for 1995–2017 combined from ATSR ADV and MODIS C6.1 and AOD tendency estimations

2018 ◽  
Vol 18 (22) ◽  
pp. 16631-16652 ◽  
Author(s):  
Larisa Sogacheva ◽  
Edith Rodriguez ◽  
Pekka Kolmonen ◽  
Timo H. Virtanen ◽  
Giulia Saponaro ◽  
...  
Keyword(s):  
Time Series ◽  
Mainland China ◽  
The North ◽  
Positive Tendency ◽  
Long Time ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Terra Modis ◽  
The Pearl River ◽  
Se China

Abstract. Understanding long-term variations in aerosol loading is essential for evaluating the health and climate effects of airborne particulates as well as the effectiveness of pollution control policies. The expected satellite lifetime is about 10 to 15 years. Therefore, to study the variations of atmospheric constituents over longer periods information from different satellites must be utilized. Here we introduce a method to construct a combined annual and seasonal long time series of AOD at 550 nm using the Along-Track Scanning Radiometers (ATSR: ATSR-2 and AATSR combined) and the MODerate resolution Imaging Spectroradiometer on Terra (MODIS/Terra), which together cover the 1995–2017 period. The long-term (1995–2017) combined AOD time series are presented for all of mainland China, for southeastern (SE) China and for 10 selected regions in China. Linear regression was applied to the combined AOD time series constructed for individual L3 (1∘ × 1∘) pixels to estimate the AOD tendencies for two periods: 1995–2006 (P1) and 2011–2017 (P2), with respect to the changes in the emission reduction policies in China. During P1, the annually averaged AOD increased by 0.006 (or 2 % of the AOD averaged over the corresponding period) per year across all of mainland China, reflecting increasing emissions due to rapid economic development. In SE China, the annual AOD positive tendency in 1995–2006 was 0.014 (3 %) per year, reaching maxima (0.020, or 4 %, per year) in Shanghai and the Pearl River Delta regions. After 2011, during P2, AOD tendencies reversed across most of China with the annually averaged AOD decreasing by −0.015 (−6 %) per year in response to the effective reduction of the anthropogenic emissions of primary aerosols, SO2 and NOx. The strongest AOD decreases were observed in the Chengdu (−0.045, or −8 %, per year) and Zhengzhou (−0.046, or −9 %, per year) areas, while over the North China Plain and coastal areas the AOD decrease was lower than −0.03 (approximately −6 %) per year. In the less populated areas the AOD decrease was small. The AOD tendency varied by both season and region. The increase in the annually averaged AOD during P1 was mainly due to an increase in summer and autumn in SE China (0.020, or 4 %, and 0.016, or 4 %, per year, respectively), while during winter and spring the AOD actually decreased over most of China. The AOD negative tendencies during the 2011–2017 period were larger in summer than in other seasons over the whole of China (ca. −0.021, or −7 %, per year) and over SE China (ca. −0.048, or −9 %, per year). The long-term AOD variations presented here show a gradual decrease in the AOD after 2011 with an average reduction of 30 %–50 % between 2011 and 2017. The effect is more visible in the highly populated and industrialized regions in SE China, as expected.

The Simulation of Drifting Dead Pigs in the Sea

2020 ◽  
Author(s):  
Yong-Jun Lin ◽  
Chih-Chung Wen ◽  
Kai-Yuan Ke ◽  
Yih-Chi Tan
Keyword(s):  
River Estuary ◽  
African Swine Fever ◽  
Ocean Currents ◽  
Western China ◽  
Jiulong River Estuary ◽  
The North ◽  
Tracking Model ◽  
Central Taiwan ◽  
The Taiwan Strait ◽  
Sea Area

<p>In 2017, dead pigs infected with African swine fever were found on the beach of Tianpu, Kinmen, an offshore island of Taiwan. After the event, the Kinmen government carried out a thorough pig farm quarantine. However, none infected pig was found in any of the pig farms. This study aims to identify where the dead infected pig came from. Affected by ocean currents, marine drifts can often reach hundreds or thousands of kilometers away from their origins. During the winter, ocean currents across the north of the Taiwan Strait from west to east may transport the pigs from the coast of Fujian and Zhejiang, China, to the coast of north-central Taiwan. Another possible driven force is the near-shore current of western China. In order to analyze the possible drifting path of pigs, the hydrodynamic model and the particle tracking model were applied. Pigs were simulated as mass particles. The simulation domain includes sea area nearby Kinmen and China where pigs may originate. Considering the effect of the currents and wind from 2018/12/26 to 2019/1/3, three possible drift scenarios were set for analysis, including (S1): originated from Weitou Bay; (S2): originated from Jiulong River estuary; (S3) originated from the coast of Quanzhou. The results showed that the most possible scenario is S3.</p>

scholarly journals Effects and Correction of Atmospheric Pressure Loading Deformation on GNSS Reference Stations in Mainland China

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Caiya Yue ◽  
Yamin Dang ◽  
Changhui Xu ◽  
Shouzhou Gu ◽  
Huayang Dai
Keyword(s):  
Time Series ◽  
Atmospheric Pressure ◽  
Northeast China ◽  
North China ◽  
Mainland China ◽  
Central China ◽  
Eastern Area ◽  
The North ◽  
North Eastern ◽  
Pressure Changes

Atmospheric pressure loading (APL) deformation is one component of nontectonic deformation for Global Navigation Satellite System (GNSS) time series and is a kind of deformation response caused by a redistribution of atmospheric pressure. In this paper, we present an atmospheric data processing strategy to compute the APL based on a spherical harmonic expansion of the global atmosphere pressure changes. We also provide a sample model to describe the relativity between the global atmosphere pressure changes and APL vertical deformation. The results show that the variation of air mass has a major impact on the north-eastern area of East China, the eastern area of North China, and Northeast China, and the vertical crustal displacement caused by the atmosphere changes in these regions can reach about 20 mm. The correction of APL for vertical time series of GNSS reference stations in different regions indicates that the arid area of the Northwest China, Northeast China, Central China, and North China are greatly affected by APL. While for the station located in Sichuan-Yunnan region, the amplitude and period change are small after correction of APL for vertical time series of GNSS reference stations, which reveals that the area is seriously affected by tectonic movement and water migration loading. The correlation between atmospheric pressure changes and crustal deformation is analyzed, which shows that APL has a serious impact on the north-eastern area of North China, the Northeast China, and the eastern area of Central China when the variations in atmospheric pressure in mainland China are the same. The research results of this paper will provide some reference value for the study of crustal structural deformation and the establishment of geodetic datum.

scholarly journals North Equatorial Current and Kuroshio Velocity Variations Affect Body Length and Distribution of the Japanese eel Anguilla japonica in Taiwan and Japan

2021 ◽  
Author(s):  
Yi-Chun Kuo ◽  
Kuan-Mei Hsiung ◽  
Yen-Ting Lin ◽  
Yu-Heng Tseng ◽  
Yu-San Han
Keyword(s):  
Drift Time ◽  
Distribution Patterns ◽  
Japanese Eel ◽  
North Equatorial Current ◽  
Larval Duration ◽  
The North ◽  
Equatorial Current ◽  
Glass Eels ◽  
Velocity Changes ◽  
Early Recruitment

Abstract The larval stage of Japanese eel travels a substantial distance over a long duration through the North Equatorial Current (NEC) and the Kuroshio, and the spawning behavior of mature eels leads to monthly arrival waves in eastern Taiwan between November and February. The total length (TL) of the glass eel relates to its larval duration and age; therefore, the TL can indicate the larval duration. The monthly mean TLs of eels along eastern Taiwan from 2010–2021 were used to estimate the batch age, and the recruitment patterns and relative abundances were compared. The TLs of glass eels followed a normal distribution, and the estimated ages were highly correlated with their mean TLs. Early recruit TLs were significantly greater than those of late recruits. The mean tracer drift time was longer in early recruitment months (November–December) than in later dates (February–March). The recruitment lag was approximately 1–1.5 months, with relative recruitment higher in the early recruitment months than in later months. Cohorts followed the main streams of the NEC and Kuroshio, and the monthly velocity changes of these currents could affect the TLs as well as the distribution patterns of Japanese glass eels in Taiwan and Japan.

New determinations of tides on the north-western Ross Ice Shelf

2020 ◽  
pp. 1-14
Author(s):  
Richard D. Ray ◽  
Kristine M. Larson ◽  
Bruce J. Haines
Keyword(s):  
Time Series ◽  
Tide Gauge ◽  
High Rate ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
The North ◽  
Global Positioning ◽  
North Western

Abstract New determinations of ocean tides are extracted from high-rate Global Positioning System (GPS) solutions at nine stations sitting on the Ross Ice Shelf. Five are multi-year time series. Three older time series are only 2–3 weeks long. These are not ideal, but they are still useful because they provide the only in situ tide observations in that sector of the ice shelf. The long tide-gauge observations from Scott Base and Cape Roberts are also reanalysed. They allow determination of some previously neglected tidal phenomena in this region, such as third-degree tides, and they provide context for analysis of the shorter datasets. The semidiurnal tides are small at all sites, yet M2 undergoes a clear seasonal cycle, which was first noted by Sir George Darwin while studying measurements from the Discovery expedition. Darwin saw a much larger modulation than we observe, and we consider possible explanations - instrumental or climatic - for this difference.

scholarly journals Time-Delay Identification Using Multiscale Ordinal Quantifiers

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 969
Author(s):  
Miguel C. Soriano ◽  
Luciano Zunino
Keyword(s):  
Time Series ◽  
Time Delay ◽  
Real World ◽  
Propagation Speed ◽  
Real World Data ◽  
External Observer ◽  
The North ◽  
Weather Phenomenon ◽  
The North Atlantic Oscillation ◽  
Finite Propagation Speed

Time-delayed interactions naturally appear in a multitude of real-world systems due to the finite propagation speed of physical quantities. Often, the time scales of the interactions are unknown to an external observer and need to be inferred from time series of observed data. We explore, in this work, the properties of several ordinal-based quantifiers for the identification of time-delays from time series. To that end, we generate artificial time series of stochastic and deterministic time-delay models. We find that the presence of a nonlinearity in the generating model has consequences for the distribution of ordinal patterns and, consequently, on the delay-identification qualities of the quantifiers. Here, we put forward a novel ordinal-based quantifier that is particularly sensitive to nonlinearities in the generating model and compare it with previously-defined quantifiers. We conclude from our analysis on artificially generated data that the proper identification of the presence of a time-delay and its precise value from time series benefits from the complementary use of ordinal-based quantifiers and the standard autocorrelation function. We further validate these tools with a practical example on real-world data originating from the North Atlantic Oscillation weather phenomenon.

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