Abstract
The widely distributed East Asian Japanese eel Anguilla japonica constitutes a single genetically homogeneous population with a single spawning area near the West Mariana Ridge. Otolith 87Sr/86Sr ratios of adults (categorized as “river“, “estuarine” or “sea” eels, according to their habitat use history determined from otolith Sr:Ca ratio analysis) collected from the spawning area in 2008 and 2009 were examined in an attempt to determine their juvenile growth areas. In addition, 87Sr/86Sr ratios of water samples from rivers in China, Taiwan, Korea, and Japan were determined. Otolith 87Sr/86Sr ratios of the “river”, “estuarine” and “sea” eels were 0.707793, 0.708580-0.709944 and 0.709068, respectively, and water sample ratios from China, Korea, Taiwan, and Japan were 0.7104320-0.7141010, 0.7190826-0.7227976, 0.7115523-0.7146914 and 0.706191-0.712484, respectively. “River” and “estuarine” eels, which had otolith 87Sr/86Sr ratios less than 0.7092 (seawater ratio), appeared to have inhabited Japanese rivers and/or estuaries because similarly low isotope ratios were recorded only from Japan. However, the juvenile growth areas of other eels were unknown, as their origins could not be determined from otolith 87Sr/86Sr ratios alone, and required further information regarding otolith elemental and isotope compositions.
Highlights
The Japanese eel Anguilla japonica is a catadromous temperate species and a high value commercial fisheries target in East Asia
Juvenile stage (“yellow eel”) Japanese eels, known to reside in freshwater, and in brackish estuarine and coastal marine habitats, can be divided into three categories based on their otolith Sr:Ca ratios according to their history of freshwater, estuarine and seawater habitat use (Tsukamoto et al 1998; Tzeng et al 2000; Tsukamoto and Arai 2001), viz “river” eels—individuals that entered and remained in freshwater river habitats after arrival of the glass eel stage in an estuary; “estuarine” eels—individuals inhabiting estuaries or moving between different habitats; and “sea” eels—individuals that at no time entered freshwater
The geology of East Asia is characterized by a greater age of bedrock formation in the continental region; the Chinese mainland comprising
Summary
The European eel is listed as critically endangered on the IUCN Red List (2011 Version), and both Japanese and American eels were considered as “threatened” in 2014 by the IUCN (Japanese eel: Jacoby and Gollock 2014; American eel: Jacoby et al 2014) Such a remarkable decline of eel stocks in the Northern Hemisphere is thought to have been caused by various anthropogenic factors, including overexploitation of stock, habitat loss due to construction of dams, weirs, sluices and culverts, pollution and disease, as well as by environmental factors, such as changes in climatic and oceanic current conditions, that are detrimental to larval recruitment (Feunteun 2002; Tatsukawa 2003; Dekker 2003; Kimura and Tsukamoto 2006; Kim et al 2007; Friedland et al 2007; Bonhommeau et al 2008; Miller et al 2009; Tsukamoto et al 2009; Itakura et al 2014; Yokouchi et al 2014; Chang et al 2015). The critical status of those eel populations has accelerated attempts to manage and restore them, involving studies on life history, including spawning and oceanic migration of larvae and maturing adults, habitat use and behavior (“yellow eel” stage) (Feunteun 2002), as well as artificial seedling production
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
