The apparent use of marine and freshwater habitats by Anguilla australis and A. dieffenbachii was examined by analyzing the strontium (Sr) and calcium (Ca) concentrations in otoliths of silver eels collected from Lake Ellesmere, which is a shallow brackish-water coastal lagoon in New Zealand. The age and growth of these eels was also examined using their otolith annuli. Size and ages of females were greater than those of males for both species. Growth rates were similar among sex and species, but the highest growth rates were observed in eels that experienced saline environments. Line analyses of Sr:Ca ratios along a life-history transect in each otolith showed peaks (ca. 15 to 21 × 10 -3 in A. australis, 14 to 20 × 10 -3 in A. dieffenbachii) between the core and elver mark, which corresponded to the period of their leptocephalus and early glass eel stage in the ocean. Outside the elver mark, the Sr:Ca ratios indicated that eels had remained in different habitats that included freshwater (average Sr:Ca ratios, 1.8 to 2.4 × 10 -3 ), areas with relatively high salinities (average Sr:Ca ratios, 3.0 to 7.4 × 10 -3 ), and in some cases individuals showed clear evidence of shifts in the salinity of their environments. These shifts either indicated movements between different locations, or changes in the salinity of the lake. There were more individuals of A. australis that used areas with intermediate or high salinities, at least for a short time (85% of individuals), than A. dieffenbachii (30%). These findings suggest that these 2 southern temperate species may have the same behavioral plasticity regarding whether or not to enter freshwater or remain in marine environments, as has been recently documented in several northern temperate anguillid species.KEY WORDS: Anguilla dieffenbachii · Anguilla australis · Age · Growth · Otolith microchemistry · Habitat use · Lake Ellesmere · New ZealandResale or republication not permitted without written consent of the publisher

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The age and migratory history of the Japanese eel, Anguilla japonica, collected along the Sanriku Coast of Japan, were examined using otolith microstructure and analysis of strontium (Sr) and calcium (Ca) concentrations. The mean Sr : Ca ratios from the elver mark to the otolith edge indicated that there were eels with several general categories of migratory history, including sea eels that never entered freshwater and others which had entered freshwater for brief periods but returned to the estuary or bay. This first evidence of the occurrence of sea eels in this northern area indicates that Japanese eels of the Sanriku Coast do not necessarily migrate into freshwater rivers.

The migratory history of Sakhalin taimen, Hucho perryi, was examined in terms of strontium (Sr) and calcium (Ca) uptake in the otolith by using wavelength dispersive X-ray spectrometry on an electron microprobe. Otolioth Sr : Ca ratios of freshwater-reared samples remained consistently at low levels throughout the otolith. The Sr : Ca ratios of samples from Lake Aynskoye of Sakhalin Island showed a low value from the core up to a point of 700-2140 µm. Thereafter, the ratios increased sharply and remained at higher levels up to the outermost regions. The difference in Sr : Ca ratio might be the result of the presence of individuals that underwent seawater and freshwater life history phases, probably reflecting the ambient salinity or the seawater-freshwater gradient in Sr concentration. Otolith Sr : Ca ratio analysis revealed downstream migration history in H. perryi.