Vol. 51 No. 1, 2012
Species Composition and Seasonal Occurrence of Recruiting
Glass Eels (Anguilla spp.) in
the Hsiukuluan River, Eastern Taiwan
Nico Jose Leander1,
Kang-Ning Shen1, Rung-Tsung Chen3, and Wann-Nian
of Fisheries Science, National Taiwan Univ., Taipei 106, Taiwan
2Department of Life Science, College of Life Science,
National Taiwan Univ., Taipei 106, Taiwan
3Endemic Species Research Institute, Chichi, Nantou
4Department of Environmental Biology and Fisheries
Science, National Taiwan Ocean Univ., Keelung 202, Taiwan
Nico Jose Leander, Kang-Ning Shen, Rung-Tsung Chen,
and Wann-Nian Tzeng (2012) There are 16 species and 3 subspecies of
freshwater eel (Anguilla spp.) found in the world. Among them, 4
species, A. japonica, A. marmorata, A. bicolor pacifica, and A. celebesensis were reported from
Taiwan. Anguilla japonica is
an important aquaculture species and is abundant on the west coast of
Taiwan, while the rest are tropical species and are more abundant on
the east coast. In addition, A.
celebesensis, which was identified in Taiwan in the past,
appears to be the new species A.
luzonensis (A. huangi)
described from northern Luzon, the Philippines. To clarify these
issues, the species composition, relative abundances, and seasonal
occurrences of anguillid eels on the east coast of Taiwan were
investigated based on 1004 glass eel specimens collected from the
estuary of the Hsiukuluan River, eastern Taiwan in 2005-2009. Eel
species were identified using morphological characters such as caudal
fin pigmentation patterns, the position of the origin of the dorsal
fin, and body proportions. The reliability of the morphological method
for species identification was checked by a DNA analysis. Anguilla marmorata was the most
abundant eel species in the Hsiukuluan River, making up 98.4% of the
total catch, while there were very few A. bicolor pacifica (1.6%) and A.
japonica (< 1%). Anguilla
marmorata recruited mainly to the estuary during spring to
summer but was found year-round, while A. bicolor pacifica recruited
mainly during autumn. Results of the DNA analysis did not support the
occurrence of A. luzonensis
and/or A. celebesensis based
on differences in the distance between the origin of the dorsal and
anal fins as a percent of total length (ADL/%TL). Anguilla celebesensis, which was
identified in the past, was not found in this study and might just be
the newly described eel species, A.
luzonensis, or just a phenotypic variation of A. marmorat . Differences in
abundances and geographic distributions of these eel species were
explained by their temperature preferences, species origins, and
current systems in the coastal waters of Taiwan.
Key words: Japanese eel, Giant mottled eel,
Indonesian shortfin eel, Glass eels, Temporal and spatial distribution.
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