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

Abstract

Otolith microstructure and microchemistry were examined in the glass eels of 5 species of Anguilla to compare the early life histories among the New Zealand temperate eels A. dieffenbachii and A. australis, and 3 species of tropical eels (A. bicolor pacifica, A. marmorata and A. celebesensis) collected in Indonesia and the Philippines. The ontogenetic patterns of fluctuation in increment widths and changes in otolith Sr:Ca ratios were similar in all species examined. They all showed an abrupt increase in increment width and a sharp drop in Sr:Ca ratio, suggesting the onset of metamorphosis from leptocephalus to glass eel. However, age at metamorphosis was different among the 5 species, as was age at recruitment to estuary (average ± SD), which was 297 ± 25.3 d in A. dieffenbachii, 268 ± 31.3 d in A. australis, 195 ± 25.8 d in A. bicolor pacifica, 170 ± 15.9 d in A. marmorata and 116 ± 17.7 d in A. celebesensis. Ages at metamorphosis and recruitment showed a linear relationship in all 5 species, and both of these ages were greater for the New Zealand temperate species than for the tropical eels. A. dieffenbachii recruited to freshwater habitats at the largest size and after the longest larval duration of any species of Anguilla ever reported. This suggests that in New Zealand A. dieffenbachii spawns at a location where their leptocephali take longer to reach their freshwater habitat than A. australis. This is in contradiction to speculation that A. dieffenbachii spawns closer to New Zealand than A. australis, based on the more advanced stage of gonadal maturation that has been observed in the silver eels of the former species.KEY WORDS: Eel · Anguilla · Early life history · Otolith · Growth increments · Sr:Ca ratios · Metamorphosis · Inshore migration Resale or republication not permitted without written consent of the publisher

Confirmation of morphological differences betweenAnguilla australis australisandA. australis schmidtii

“…Ecological factors such as spawning areas, larval transport routes, or water temperature during development, are also important for evaluating the taxonomic status of the two subspecies of A. australis. Though several ecological studies of the life history and biology of glass eels have been conducted, research on the early life history of A. australis during its oceanic phase is still insufficient (Aoyama et al 1999;Arai et al 1999;Marui et al 2001 ;Shiao et al 2001). Most researchers have assumed that leptocephali travel to Australia on the East Australian Current (Schmidt 1928;Cairns 1941;Sloane 1984;Jellyman 1987;Beumer & Sloane 1990;Shiao et al 2001), which originates from the South Equatorial Current and flows along the eastern seaboard of Australia (Wyrtki 1962;Church 1987).…”

“…Subsequently, Dijkstra & Jellyman (1999) sequenced the control region (611 base pairs) of the mitochondrial DNA (mtDNA) of specimens identified as A. australis australis and A. australis schmidtii, and concluded the two subspecies share a common gene pool. Based on the genetic studies, several recent ecological papers (Aoyama et al 1999;Arai et al 1999;Jellyman et al 1999;Marui et al 2001 ;Shiao et al 2001) eels from Australia and New Zealand as A. australis without commenting on morphological differences between the populations. Jellyman (1987) recognised seasonally consistent differences in number of vertebrae of the glass eels that recruited to New Zealand, and speculated that variations in water temperature during the hatching of eggs could account for the differences.…”

Effects of metamorphosis timing and the larval growth rate on the latitudinal distribution of sympatric freshwater eels, Anguilla japonica and A. marmorata, in the western North Pacific

“…Because otolith increments in A. marmorata and A. japonica were confirmed to be deposited on a daily basis (Tabeta et al 1987;Umezawa et al 1989;Sugeha et al 2001b), the increment number was considered as the daily age in each individual examined in the present study. The drastic change in otolith Sr/Ca from the primordium to the otolith edge coincided with major life history events in the life of the young eels, like first feeding, metamorphosis, etc., as reported in previous studies for both temperate and tropical anguillid species Tsai 1992, 1994;Otake et al 1994;Tzeng 1996;Arai et al 1997Arai et al , 1999aCieri and McCleave 2001;Marui et al 2001). The age of the leptocephalus at the onset of metamorphosis (T m ) was determined from the number of DGIs between the primordium (P) and MC where the increment pattern and Sr/Ca ratios dramatically changed (Otake et al 1994Tzeng and Tsai 1994;Tzeng 1995;Kuroki et al 2005;Arai et al 2002a).…”

Inshore migration of the tropical eels Anguilla spp. recruiting to the Poigar River estuary on north Sulawesi Island

“…The spawning location and season have been described for some species of temperate eels (Schmidt 1922, Tsukamoto 1992, and there have been various studies on the glass eels Anguilla japonica (Matsui 1952, Tzeng 1985, Tsukamoto 1990, Cheng & Tzeng 1996, Arai et al 1997, A. anguillla (Deelder 1952, Creutzberg 1958, Gandolfi et al 1984, Gascuel 1986, Tongiorgi et al 1986, Lecomte-Finiger 1992, Arai et al 2000, A. rostrata (Sorensen 1986, Sorensen & Bianchini 1986, Wippelhauser & McCleave 1987, Haro & Krueger 1988, Martin 1995, Wang & Tzeng 1998, Arai et al 2000), and A. australis and A. dieffenbachi (Jellyman 1977, 1979, Todd 1981, Sloane 1984, Arai et al 1999b, Jellyman et al 1999, Marui et al 2001. Some of these studies have described the larval duration and growth, timing of metamorphosis and recruitment to coastal waters, or timing of inshore migration of glass eels and elvers in relation to environmental factors such as temperature, salinity, tide cycle, and lunar phase.…”