Summer daytime habitat and population density of the torrent catfish, Liobagrus reini, in the Urano River

Abstract

The population density and summer daytime habitat characteristics of the endangered torrent catfish, Liobagrus reini, in the Urano River, a tributary of the Chikuma River in Nagano, central Japan, were investigated. A total of 105 individuals were captured in 2001–2003, and the estimated population density 100 m−2 in the whole study area ranged from 0.20 to 2.96. Liobagrus reini were captured from under cobbles and boulders, interstices in bedrock, and in clumps of roots of terrestrial vegetation along banks. Compared with the distribution of physical factors in the study area, the fish selected shallow habitats with the riverbed covered by cobbles and boulders. Boulders and larger cobbles were chosen by larger individuals as a habitat. Habitat selection was not correlated with current velocity, and some individuals were sampled near (<1 m) the riverbank with no current. For the conservation of L. reini, the preservation of natural riverbanks and areas with boulders and large cobbles in the riverbed is concluded to be important.