Metamorphosis and inshore migration of tropical eels Anguilla spp. in the Indo-Pacific

Abstract

In order to determine the early life history and recruitment mechanisms of tropical eels AnguiUa spp. in the Indo-Pacific, the timing of metamorphosis and age at recruitment to freshwater habitats were established from otolith microstructure and microchemistry analyses of juveniles of Anguilla celebesensis, A. rnarrnorata and A. bicolor bicolor. Otolith increment width markedly bicolor bicolor. In all species exam~ned, close linear relationships were found between ages at metamorphosis and recruitment, suggesting that individuals which metamorphosed earlier were recruited to freshwater habitats at a younger age.

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

“…Anguilla australis sampling sites, dates and sample sizes collected from 6 Australian estuaries (Sites A1 to A6) and 2 New Zealand estuaries (Sites A7 to A8) (sites are shown in Fig. 1 The timing of metamorphosis from leptocephali to glass eels was determined from the drastic increase of increment width coinciding with the decrease in Sr:Ca ratios (Otake et al 1994, Tzeng & Tsai 1994, Arai et al 1997, Wang & Tzeng 1998, Arai et al 1999a. However, some checks were formed in the otoliths after the glass eels entered the estuaries.…”

“…The decrease in the Sr:Ca ratio coincided with a drastic increase in increment width. The simultaneous changes in increment width and Sr:Ca ratio indicates metamorphosis from the leptocephalus to the glass eel stage (Otake et al 1994, Tzeng & Tsai 1994, Arai et al 1997, Wang & Tzeng 1998, Arai et al 1999a.…”

“…together with the microchemistry analysis of otoliths, has been extensively used to study the early life history of freshwater eels (Tzeng 1990, Otake et al 1994, Tzeng & Tsai 1994, Arai et al 1999a. Arai et al (1999c) recently determined the age of Anguilla australis on a daily basis and found that the glass eels recruited to Australia (208 ± 17.4 d) were ca 20 to 30 d younger than those recruited to New Zealand (232 ± 19.8 d western coast, 237 ± 20.0 d eastern coast).…”

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

“…For electronmicroprobe analyses, all otoliths (69 specimens) were carbon or Pt-Pd coated by high-vacuum evaporator. Otoliths from 61 specimens were used for 'life-history transect' analysis of Sr and Ca concentrations, which were measured along a line down the longest axis of each otolith from the core to the edge using a wavelength dispersive X-ray electron microprobe (JEOL JXA-8900R or JXA-733), as described by Arai et al (1997Arai et al ( , 1999a and Arai & Tsukamoto (1998). Strontianite (SrCO 3 ) and calcite (CaCO 3 ) were used as standards.…”

Caracteristiques Biologiques Des Civelles (Anguilla Anguilla) Lors De La Transition en Estuaire.

“…Les stades de pigmentation (ELIE et al, 1982) ne peuvent être considérés comme un indice du temps passé en estuaire car la température influence davantage le processus de mélanisation des cellules que le temps. L'étude des microstructures des otolithes de civelles est largement répandue sur différentes espèces du genre Anguilla (ARAI et al, 1997 ;ARAI et al, 1999 ;ARAI et al, 2000). L'objectif de ce travail est de mettre en parallèle la formation de la double marque de transition en estuaire et le développement de la pigmentation à partir de l'étude des lots de civelles capturées en mer et en estuaire.…”