Demographics of eels in the Hamana

Demographics of eels in the Hamana Lake system
The intensive electrofishing sampling continuously
along a 3-km stretch of the Nishijinden River showed
a tendency of the size of Japanese eels to increase
and their relative abundance to decrease with distance
from the river mouth. This tendency was also
suggested for Japanese eels in the Tanshui River of
northern Taiwan (Tzeng et al. 1995) and for American
(Haro & Krueger 1991; Smogor et al. 1995;
Oliveira 1997; Goodwin & Angermeier 2003) and European eels (Naismith & Knights 1988, 1993;
Feunteun et al. 2003; Laffaille et al. 2003; Moriarty
2003; Lasne & Laffaille 2008) in various different
sizes of rivers. These observations suggest that this
type of distribution pattern is not locally determined,
but is a general ecological trait for temperate
anguillid species. Such a distribution pattern of
anguillid eels in riverine habitats might be explained
by two alternative mechanisms: (1) eels colonise the
length of the river uniformly after river recruitment,
and those settled in upstream areas grow faster than
in lower reaches; and (2) eels move towards upstream
reaches gradually as they grow larger and this results
in the difference in age structure between the
upstream areas and lower reaches.

Hasil (Bahasa Indonesia) 2:

Demografi belut dalam sistem Hamana Danau
intensif elektro fi shing pengambilan sampel secara terus menerus
sepanjang 3 km bentangan Sungai Nishijinden menunjukkan
kecenderungan ukuran belut Jepang untuk meningkatkan
dan kelimpahan relatif mereka menurun dengan jarak
dari muara sungai. Kecenderungan ini juga
disarankan untuk belut Jepang di Sungai Tanshui dari
Taiwan utara dan untuk Amerika (Tzeng et al 1995.)
(Haro & Krueger 1991; Smogor et al 1995;.
Oliveira 1997; Goodwin & Angermeier 2003) dan belut Eropa (Naismith & Knights 1988, 1993;
Feunteun et al 2003;. Laffaille et al 2003;. Moriarty
2003; Lasne & Laffaille 2008) dalam berbagai berbeda
ukuran sungai. Pengamatan ini menunjukkan bahwa ini
jenis pola distribusi tidak secara lokal ditentukan,
tetapi sifat ekologis umum untuk beriklim
spesies anguillid. Seperti pola distribusi
belut anguillid di habitat sungai mungkin dijelaskan
oleh dua mekanisme alternatif: (1) belut menjajah
panjang sungai seragam setelah perekrutan sungai,
dan mereka menetap di daerah hulu tumbuh lebih cepat daripada
di hilir; dan (2) belut bergerak menuju hulu
mencapai secara bertahap saat mereka tumbuh lebih besar dan hasil ini
dalam perbedaan struktur umur antara
daerah hulu dan hilir.