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

Abstract

Background: Early life history traits of the temperate eel Anguilla japonica and tropical eel Anguilla marmorata were examined to determine the possible reason why these two species have similar spawning areas and oceanic larval transport in the North Equatorial Current and yet are recruited to different but partly overlapping continental growth habitats in northern East Asia. To understand the segregative migration of these two sympatric eel species, their glass eels were collected from nine estuaries in the Philippines, Taiwan, Japan, and China. The age at metamorphosis from leptocephalus to glass eel (T m ), the age at estuarine arrival (T t ), the time between metamorphosis and estuarine arrival (T t−m ), and the growth rate (G t ) of glass eels were calculated from daily growth increments in their otoliths. Results: Results indicated that the G t was faster and the T m was younger in A. marmorata than in A. japonica. On the other hand, fish length and the T t at estuarine arrival were larger in A. japonica than in A. marmorata, indicating that elvers of A. japonica experience a longer oceanic drift than those of A. marmorata. In addition, the T t−m also indicated that A. japonica experienced a longer coastal migration than A. marmorata.

Growth rate variability of larval European eels (Anguilla anguilla) across the extensive eel spawning area in the southern Sargasso Sea

“…The individual growth increments outside the defined FFC are composed of a calcium carbonate‐rich ring abutting a protein‐rich ring. Together these pairs produce a distinctive and characteristic, translucent‐opaque concentric ring pattern in SEM after the polishing and etching (Lecomte‐Finiger, ; Leander, Tzeng, Yeh, Shen, & Han, ). Only infrequently (~5% of otoliths) could ring patterns be distinguished within the FFC.…”

The ecology of oceanic dispersal and survival of anguillid leptocephali

“…5B). No small A. marmorata leptocephali have been collected in the Indonesian Seas (Aoyama et al 2003), which, along with the findings of population structure studies (Minegishi et al 2008), indicates that the larvae of the North Pacific population disperse widely to regions along the western and southern margins of the western North Pacific after spawning in the NEC Han et al 2012a;Leander et al 2013).…”

“…Timing of metamorphosis is likely an important aspect of this (Wang and Tzeng 2000;Leander et al 2013); however, it seemingly cannot explain the entire differences in transport and recruitment patterns without a component of active behavior by the leptocephali or glass eels. In each of the known cases of individual current systems transporting multiple species of anguillid larvae that have different final destinations (Gulf Stream, NECKuroshio Current, East Australian Current), the early initiation of metamorphosis can prepare the larvae that recruit to the closest locations for entering coastal waters as glass eels, but some kind of active behavior is required to ensure that they exit the currents and reach the coastal waters.…”

“…1). These Northern Hemisphere anguillid eels are temperate species, but the North Pacific population of the giant mottled eel (Anguilla marmorata), a tropical species, also spawns offshore in the NEC in an overlapping area with A. japonica, and its leptocephali disperse even more widely Han et al 2012a;Leander et al 2013). The newly discovered species the Luzon eel (Anguilla luzonensis) may also spawn in the same area (Kuroki et al 2012).…”

Location, size and age at onset of metamorphosis in the Japanese eel Anguilla japonica

“…Unlike A. japonica, which is distributed widely across East Asia, A. luzonensis tends to be concentrated in the southernmost part of East Asia around Luzon Island due to its short and narrow range of larval duration (Han et al, 2016). Similarly, although the leptocephalus distribution and spawning area of Anguilla marmorata Quoy & Gaimard 1824 overlap with those of the A. japonica Kuroki et al, 2009), there are latitudinal differences in their growth habitats, probably due to differences in their larval durations (Leander et al, 2013).…”