Determination of the freshwater mark in otoliths of Japanese eel elvers using microstructure and Sr/Ca ratios
| Autor: | Noritaka Mochioka, Yutaka Kawakami, Akinobu Nakazono, Hidetoshi Toh, Koichiro Morishita |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
geography
geography.geographical_feature_category biology Mineralogy Estuary Aquatic Science biology.organism_classification Salinity Fishery medicine.anatomical_structure Fresh water Anguillidae Nature Conservation medicine Environmental science Japanese eel Bay Ecology Evolution Behavior and Systematics Otolith |
| Zdroj: | Environmental Biology of Fishes. 53:421-427 |
| ISSN: | 1573-5133 0378-1909 |
| DOI: | 10.1023/a:1007429332507 |
| Popis: | The microstructure, in particular checks within the otolith edge, of Anguilla japonica glass-eels and elvers and changes in otolith Sr/Ca ratios were examined to ascertain the environmental history of the eels, especially with regard to the time when glass-eels entered the river, and as a benchmark for count daily increments. The percentage of glass eels and elvers with checks and the mean number of checks within the otoliths of glass-eels caught at four localities, Tosa Bay off Tosa City, the mouth of the Gokase River, the mouth of the Saigo River and the dam of the Tsuri River were 0% (0), 15.0% (0.2), 51.6% (1.0) and 100.0% (4.2), respectively. The Sr/Ca ratios and Sr content peaked in the region where checks were formed and the values decreased rapidly towards the edge of the checks; on the other hand, these decreased gradually in the otolith when checks were not formed. These checks were estimated to be formed by stress when the glass-eels were affected by ambient fresh water within the river. The innermost check was called the ‘freshwater mark’ in the present study and this mark may be useful as a benchmark in studying the growth history of the eel before and after entering freshwater. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full text from SpringerLink