Drastic changes in otolith strontium/calcium ratios in leptocephali and glass eels of Japanese eel Anguilia /aponica

Abstract

Strontium (Sr) and calcium (Ca) contents and Sr/Ca ratios in otoliths of Japanese eel Anguilla japonica leptocephali and glass eels were examined. The Ca content was almost constant throughout the otoliths, except for the core, in which it was lower. Both Sr content and Sr/Ca ratios increased with age during the leptocephalus stage, but dramatically decreased at age 90 to 100 d. The otolith increment width also showed marked variation at ages 80 to 110 d, indicating the period of metamorphosis. These suggest that the changes in Sr content and Sr/Ca ratios are associated with metamorphosis. X-ray intensity maps revealed that the Sr content in glass eel otoliths increased for short periods at ages of about 20,50 and 90 d. Such changes seem to be related to events, such as beginning of vertical migration or differing current influences, occurring during the oceanic migration of Japanese eel leptocephali.

Facultative catadromy of the eel Anguilla japonica between freshwater and seawater habitats

“…Otake et al (1994) found an ontogenetic change in the Sr/Ca ratios in the otoliths of Anguilla japonica glass eels at the onset of metamorphosis that was indicated by an abrupt drop in the high Sr level maintained during the leptocephalus stage. Similar results were confirmed in tropical eels (A. celebesensis, A. marmorata, A. bicolor bicolor and A. bicolor pacifica: Arai et al 1999a,b) and other temperate eels in the southern hemisphere (A. australis: Arai et al 1999c;A.…”

Migratory behaviour and habitat use by American eels Anguilla rostrata as revealed by otolith microchemistry

“…(Otake et al 1994, Tzeng & Tsai 1994, Tzeng 1996, Tzeng et al 1997, 2000, in press, Secor 1999, Secor & Rooker 2000. The variability in migratory behaviours associated with habitat selection has recently been investigated for leptocephali metamorphosing to glass eels over the continental shelf (Cheng & Tzeng 1996, Wang & Tzeng 1998, 2000, Arai et al 2000, Shiao et al 2001) and for estuarine-and freshwater-resident yellow and silver eels (Tzeng et al 1997).…”

Decreased Sr/Ca ratios in the otoliths of two marine eels, Gymnothorax reticularis and Muraenesox cinereus, during metamorphosis

“…The Sr/Ca ratios in the otoliths of Japanese eels Anguilla japonica drastically decrease when the eel larvae pass through a salinity gradient during migration from spawning ground to estuary while simultaneously transitioning from the leptocephalus to glass eel developmental stage (Tzeng & Tsai 1994). Otake et al (1994) suggested that this sharp decrease in Sr/Ca ratios marks the onset of metamorphosis. However, no direct evidence was given to validate this claim.…”