Differences in the early life history of the Australasian shortfinned eel Anguilla australis from Australia and New Zealand, as revealed by otolith microstructure and microchemistry

Abstract

Otolith microstructure and microchemistry were examined in juveniles of Australasian shortfinned eel, Anguilla australis, from Australia and New Zealand. Patterns in otolith increment widths were similar in these two stocks. A marked increase in otolith increment width was found from age 138 to 198 d (mean ± SD: 164 ± 18.6 d) from Australia, 161 to 208 d (185 ± 17.3 d) from the western coast of New Zealand and 161 to 211 d (187 ± 18.9 d) from the eastern coast. These changes coincided with a drastic decrease in otolith Sr:Ca ratios, suggesting that metamorphosis began at these ages in each species. The duration of metamorphosis estimated from otolith microstructure was the same in the different stocks, 17 to 41 d (mean ± SD: 27 ± 5.4 d). Ages at recruitment were 186 to 239 d (mean ± SD: 208 ± 17.4 d) from Australia, 214 to 263 d (232 ± 19.8 d) from the western coast of New Zealand and 208 to 266 d (237 ± 20.0 d) from the eastern coast. There was a significant difference in the age between the Australian stock and the two stocks from New Zealand. No significant difference was found in the age between the latter two stocks. The difference in the period for the recruitment between Australian and New Zealand stocks seems to reflect their geographical separation.