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Vol. 52, 2013
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
Nico
Jose Leander1, Wann-Nian Tzeng1,2*, Nian-Tzu Yeh1,
Kang-Ning Shen1,2 and Yu-San Han1
1Institute
of Fisheries Science, College of Life Science, National Taiwan
University, Taipei 10617, Taiwan
2Department of Environmental Biology and Fisheries
Science, National Taiwan Ocean University, Keelung 20224, Taiwan
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 (Tm), the age
at estuarine arrival (Tt),
the time between metamorphosis and estuarine arrival (Tt−m), and the growth
rate (Gt) of glass
eels were calculated from daily growth increments in their otoliths.
Results: Results indicated that the Gt was faster and the Tm was younger in A. marmorata than in A. japonica. On the other hand,
fish length and the Tt 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 Tt−m also indicated that A. japonica experienced a longer
coastal migration than A. marmorata.
Conclusions: This study validated
that the Tm and Gt seem to play important roles in the
segregative migration and latitudinal distribution of these two
sympatric freshwater eel species in the northwestern Pacific.
Key words: Otolith; Daily growth increment;
Japanese eel; Giant mottled eel; Larval migration.
*Correspondence: E-mail: wnt@ntu.edu.tw
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