[pp.159-166]

‹Research Report›Comparison of Fish Assemblages in Drainage Ditches of Rice Fields in Lake Biwa Basin, Jap

Yosihiro NATUHARA and Yoshihiro AKIYAMA （Nagoya University）

Abstract:
We conducted a fish survey of 18 rice field drainage ditches in the northern Lake Biwa Basin, Shiga Prefecture, Japan, from 28 September to 5 October 2010. In total, 2,366 individuals of 30 freshwater fish taxa were collected. The species richness of fish collected from each ditch ranged from 2 to 14 species. The physical environment varied among the studied ditches despite all ditches being paved with concrete or concrete flume and connected to rice fields via pipes. Some ditch had a sediment at the bottom. Species richness was higher in ditches with the bottom accumulated with mud and gravel, and positively correlated with water depth of the ditch. Fish and study sites were each classified into four groups by detrended correspondence analysis. Fish assemblages were affected by the sediment type, water temperature, and width of the ditch and location of the study site. The abundance of some species, such as Cobitis biwae and Tanakia lanceolata, was positively correlated with species richness in the ditch.

Key Word:
biodiversity, freshwater fish, rice field, drainage ditch

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