Collection of spawning-condition eels of Ariosoma meeki in the Kuroshio Current in the East China Sea

2016 ◽  
Vol 96 (8) ◽  
pp. 1701-1707 ◽  
Author(s):  
Shun Watanabe ◽  
Seishi Hagihara ◽  
Michael J. Miller ◽  
Masamichi Machida ◽  
Kosei Komatsu ◽  
...  
Keyword(s):  
Continental Shelf ◽  
East China Sea ◽  
Seminal Fluid ◽  
Kuroshio Current ◽  
East China ◽  
The East China Sea ◽  
Reproductive Condition ◽  
China Sea ◽  
Gonad Somatic Index ◽  
The Kuroshio

When and where marine eels spawn is poorly known even though species such as those of the family Congridae, Muraenidae and Ophichthidae can be caught in continental shelf habitats. The congrid genus Ariosoma includes small continental shelf eel species whose life histories are not yet known. Mature male and female eels of Ariosoma meeki were observed and captured on 17 August 2009 at the surface at night in the western side of the Kuroshio Current in the East China Sea close to new moon, while they were swimming slowly at the surface and exhibiting apparent reproduction-related behaviour. One male and one sex-unidentified eel (seemingly a male based on body shape) were observed to be chasing one larger female with their heads located near her urogenital pore area. The gonads of the female (540 mm) and the male (410 mm) that were caught by a long-handled dip net were in reproductive condition, because some eggs or seminal fluid were released during handling of the two specimens and high gonad-somatic index (GSI) values of 53 in the female and 20 in the male were recorded. This is one of the few cases in which fully ripe reproductive-condition marine eels have been observed or collected and it provides rare information about the spawning location and timing of this eel species.

scholarly journals Variability of the nutrient stream near Kuroshio's origin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chen-Tung Arthur Chen ◽  
Ting-Hsuan Huang ◽  
Chi-Hsuan Wu ◽  
Haiyan Yang ◽  
Xinyu Guo
Keyword(s):  
Pacific Ocean ◽  
Continental Shelf ◽  
East China Sea ◽  
Kuroshio Extension ◽  
Subsurface Water ◽  
East China ◽  
The East China Sea ◽  
High Productivity ◽  
China Sea ◽  
The Kuroshio

AbstractThe Kuroshio—literally “the Black Stream”—is the most substantial current in the Pacific Ocean. It was called the Black Stream because this oligotrophic current is so nutrient-poor in its euphotic zone that the water appears black without the influence of phytoplankton and the associated, often colored dissolved organic matter. Yet, below the euphotic layer, nutrient concentrations increase with depth while current speed declines. Consequently, a core of maximum nutrient flux, the so-called nutrient stream, develops at a depth of roughly between 200 and 800 m. This poorly studied nutrient stream transports nutrients to and supports high productivity and fisheries on the East China Sea continental shelf; it also transports nutrients to and promotes increased productivity and fisheries in the Kuroshio Extension and the subarctic Pacific Ocean. Three modes of the Kuroshio nutrient stream are detected off SE Taiwan for the first time: one has a single-core; one has two cores that are apparently separated by the ridge at 120.6–122° E, and one has two cores that are separated by a southward flow above the ridge. More importantly, northward nutrient transports seem to have been increasing since 2015 as a result of a 30% increase in subsurface water transport, which began in 2013. Such a nutrient stream supports the Kuroshio's high productivity, such as on the East China Sea continental shelf and in the Kuroshio Extension SE of Japan.

scholarly journals Water Exchange across Isobaths over the Continental Shelf of the East China Sea

2017 ◽  
Vol 47 (5) ◽  
pp. 1043-1060 ◽  
Author(s):  
Jing Zhang ◽  
Xinyu Guo ◽  
Liang Zhao ◽  
Yasumasa Miyazawa ◽  
Qun Sun
Keyword(s):  
Continental Shelf ◽  
East China Sea ◽  
Water Exchange ◽  
Bottom Layer ◽  
Taiwan Strait ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
The Taiwan Strait ◽  
The Kuroshio

AbstractOnshore and offshore currents and the associated volume transport across three isobaths (50, 100, and 200 m) over the continental shelf of the East China Sea were examined using daily reanalysis data in 1993–2012. After being averaged along the isobaths, the velocities across 100 and 50 m are onshore in the bottom layer but offshore in the surface layer. In contrast, those across the 200-m isobath are onshore in the surface and bottom layers but without a clear direction in the midlayer, suggesting a three-layer structure. The surface offshore current across the 100-m isobath mainly arises from the Taiwan Strait Current, while the surface onshore current across the 200-m isobath mainly arises from the Kuroshio, both of which converge in the area between the 100- and 200-m isobaths and flow toward the Tsushima Strait. The control of bottom Ekman dynamics on the onshore bottom currents is important at the 100-m isobath, partly important at the 200-m isobath, and slightly important at the 50-m isobath. The seasonal variations of onshore and offshore currents in the surface layers across the three isobaths are likely caused by local winds, the Taiwan Strait Current, and the Changjiang discharge, while those in midlayer across the 200-m isobath demonstrate a strong geostrophic control and can be interpreted from a traditional viewpoint on the Kuroshio intrusion over the entire water column across the shelf slope. The close connection of bottom onshore currents across the three isobaths suggests that the bottom layer is an important pathway for water exchange of shelf water and the open sea.

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