2013 年 60 巻 1 号 p. 43-48
Owing to growing concern regarding the declining numbers of Far Eastern catfish, Silurus asotus, associated with and formerly abundant around paddy fields, a census of the species was conducted in the shallow lotic environment of a paddy field channel in 2008 and 2009. Although such a channel has been conventionally regarded as unsuitable as S. asotus habitat, a total of 707 adults were observed overall, eggs being collected during 30 of 58 egg census visits. A significant positive correlation existed between the number of S. asotus adults and eggs. Adult catfish were observed almost exclusively at night when the water was deep, suggesting that most entered the channel at night for spawning. Such paddy-associated channels appear to function at least partly as alternative spawning sites when paddy fields are not accessible.