Dispersal Characteristics and Pathways of Japanese Glass Eel in the East Asian Continental Shelf

Abstract

The Japanese eel Anguilla japonica is an important aquaculture fish species in the East Asian countries of Japan, China, Korea, and Taiwan. All glass eel fry are captured from the wild and understanding the recruitment patterns of the glass eel is important. The larvae of A. japonica are passively transported to the East Asian Continental Shelf by the North Equatorial Current, the Kuroshio, the Kuroshio intrusion currents, and coastal currents. In each location, recruitment time is diverse: It is November in Taiwan and April in the Yalu River. How the glass eels reach recruitment areas remains poorly understood. Here, we combine information from larval ages based on otolith increments, simulated drifting paths on the East Asian Continental Shelf, and main fishing seasons in each location of East Asia. We identify five main recruitment blocks: (1) The main Kuroshio, (2) The Taiwan Strait Warm Current, (3) The Taiwan Warm Current, (4) The Yellow Sea Warm Current and (5) The branch of Yellow Sea Warm Current. The counted age of the glass eels is significantly underestimated for the later recruits, possibly due to the cessation of the otolith edge growth under low water temperatures. This study clarifies the eel’s larval characteristics and transport mechanisms in the East Asia Continental Shelf, providing important information for its recruitment dynamics in the marine stage.

Ecology and evolution of migration in the freshwater eels of the genus Anguilla Schrank, 1798

“…A variety of recent advancements made by means of molecular genetic and ecological studies have better elucidated the ecology and evolution of anguillid eels. Scales of spawning migration distinctly differ among tropical eel species (Aoyama et al, 2003(Aoyama et al, , 2018Robinet et al, 2008;, 2009Schabetsberger et al, 2013Schabetsberger et al, , 2015Arai, 2014a;Arai and Abdul Kadir, 2017a;Han et al, 2019;Hewavitharane et al, 2020). Less than 100 km of small-scale migration and 1000-3000 km of mid-scale migration are suggested in A. clelebesensis and A. borneensis (Aoyama et al, 2003(Aoyama et al, , 2018Arai, 2014a) and A. marmorata, A. bicolor bicolor, A. mossambica and A. bengalensis bengalensis (Robinet et al, 2008;, 2009Arai, 2014a;Arai and Abdul Kadir, 2017a;Aoyama et al, 2018;Han et al, 2019), respectively.…”

“…Scales of spawning migration distinctly differ among tropical eel species (Aoyama et al, 2003(Aoyama et al, , 2018Robinet et al, 2008;, 2009Schabetsberger et al, 2013Schabetsberger et al, , 2015Arai, 2014a;Arai and Abdul Kadir, 2017a;Han et al, 2019;Hewavitharane et al, 2020). Less than 100 km of small-scale migration and 1000-3000 km of mid-scale migration are suggested in A. clelebesensis and A. borneensis (Aoyama et al, 2003(Aoyama et al, , 2018Arai, 2014a) and A. marmorata, A. bicolor bicolor, A. mossambica and A. bengalensis bengalensis (Robinet et al, 2008;, 2009Arai, 2014a;Arai and Abdul Kadir, 2017a;Aoyama et al, 2018;Han et al, 2019), respectively. Compared to their migration scales, however, temperate anguillids, such as A. rostrata (1000-5000 km; mid-to large-scale migration) and A. anguilla (5000-8000 km; large-scale migration), exhibit larger migration scales (Aoyama et al, 2003;Miller et al, 2019).…”

“…The long larval duration from approximately 3 to 24 months in anguillid eels (e.g. Tsukamoto, 1990;Lecomte-Finiger, 1992;Cheng and Tzeng, 1996;Arai et al, 1999aArai et al, , 2000Wang and Tzeng, 2000;Marui et al, 2001;Robinet et al, 2003aRobinet et al, , 2008, 2009Bonhommeau et al, 2010;Han et al, 2016aHan et al, , 2019Hewavitharane et al, 2020) seems to highly adjust marine planktonic life. Passive transportation by oceanic currents and winds during the slow leptocephalus growth would facilitate the global dispersion almost across the world.…”

“…The lengthy duration of the larval stage might lead to global dispersion and their consequent speciation. The durations of leptocephalus stages span from several months to approximately two years (e.g., Tsukamoto, 1990 ; Lecomte-Finiger, 1992 ; Cheng and Tzeng, 1996 ; Arai et al., 1999a , 2001 ; 2003a ; Wang and Tzeng, 2000 ; Marui et al., 2001 ; Robinet et al., 2003a ; Robinet et al., 2008 ; Réveillac et al., 2008 , 2009 ; Bonhommeau et al., 2010 ; Han et al., 2016a , 2019 ; Hewavitharane et al., 2020 ). Many marine organisms have a planktonic larval stage during their early life and larvae are passively transported by oceanic currents.…”

Impacts of the Kuroshio and Tidal Currents on the Hydrological Characteristics of Yilan Bay, Northeastern Taiwan

“…A volcanic island, Guishan Island, is in the bay; there are hydrothermal vents near the island [1,2], which discharge hydrothermal fluid containing sulfur particles [3], cause carbonate chemical changes in shallow water areas [4][5][6], and affect the habitat of crabs [7], shrimps [8], and fish [9]. In addition, the flow field in the bay also affect the pathways of eels [10,11].…”