Validation of otolith daily increments in the tropical eel Anguilla celebesensis

Abstract

To validate daily increments in otoliths of the tropical freshwater eel Anguilla celebesensis, a time-reference mark was incorporated in the otoliths of glass eels by immersing the eels in alizarin complexone (ALC) solution. They were subsequently reared in aquaria for 10 or 20 days, and the increments outside a fluorescent red ALC mark were counted. The numbers from the 10- and 20-d experiments were 9.4 ± 0.9 (mean ± SD) and 19.4 ± 1.4, respectively, suggesting daily deposition of otolith increments. Precise examination of otolith microstructure from the core to the edge showed gradual changes in increment width with no discontinuous structural features, suggesting that increments were deposited continuously from hatching to time of sacrifice. It was thus concluded that otolith increments in this species can be used for daily age determination.

Comparison of early life history between New Zealand temperate eels and Pacific tropical eels revealed by otolith microstructure and microchemistry

“…Data of Sr and Ca contents around the measurement points were assigned to each 10 growth increments and used for life history transect analysis. Otolith increments of Anguilla japonica (Tsukamoto 1989, Umezawa et al 1989, A. rostrata (Martin 1995) and A. celebesensis (Arai et al 2000a) have been validated as being deposited daily, so we assumed that the species studied here also deposited increments daily. Early life history parameters.…”

“…The age at deposition of the hatching check was considered as Day 0. The yolk absorption check was the second check outside the central hole, and was visible as a deep dark groove surrounding a crystalline crown just outside the hatch check in A. celebesensis (Arai et al 2000a). The innermost check on the otolith edge was regarded as a freshwater check which was formed when the glass eel entered freshwater (Kawakami et al 1998, Arai et al 1999b.…”

“…The daily deposition of otolith increments has been validated in A. japonica (Tsukamoto 1989, Umezawa et al 1989, A. rostrata (Martin 1995) and A. celebesensis (Arai et al 2000a). It has also been found that microstructural characteristics such as hatch check (Umezawa et al 1989), yolk absorption check (Arai et al 2000a), freshwater check (Kawakami et al 1998) and a drastic increase in increment width, indicating onset of metamorphosis (Otake et al 1994, Arai et al 1997, are useful in interpreting individual life history events.…”

“…The daily deposition of otolith increments has been validated in A. japonica (Tsukamoto 1989, Umezawa et al 1989, A. rostrata (Martin 1995) and A. celebesensis (Arai et al 2000a). It has also been found that microstructural characteristics such as hatch check (Umezawa et al 1989), yolk absorption check (Arai et al 2000a), freshwater check (Kawakami et al 1998) and a drastic increase in increment width, indicating onset of metamorphosis (Otake et al 1994, Arai et al 1997, are useful in interpreting individual life history events. However, this information has been obtained mainly from northern hemisphere temperate eels (A. japonica, A. anguilla and A. rostrata), and only recently has the otolith microchemistry of a few Indo-Pacific tropical eel species (Arai et al 1999c,d) and the southern temperate species A. australis (Arai et al 1999b) been examined in glass eels.…”

Dispersal pattern of glass eel stage of Anguilla australis revealed by otolith growth increments

“…We assumed that the growth increments in otoliths of Anguilla australis were deposited on a daily basis, as are those of A. japonica, A. rostrata and A. celebesensis, which have been validated (Umezawa et al 1989, Martin 1995, Arai et al 2000. The present study found that the Australiasian eel A. australis took approximately 7 to 9 mo to drift from the spawning grounds to the estuaries of Australia and New Zealand (Table 3), and metamorphosis from leptocephalus to glass eel occurred approximately 5 to 6 mo after hatching.…”