Relationship between Water Quality and Occurrence of Freshwater Fish in First-Grade River Systems in Northern Kyushu, Japan

Abstract

We analyzed the relationship between water quality and freshwater fi sh in major fi rst-grade river systems in northern Kyushu, Japan. The number of fi sh species preferring fl owing water showed a signifi cant negative correlation with BOD, while that of fi sh species preferring standing water showed no correlation with BOD. The results of receiver operating characteristic curve analysis indicated statistical relationships between the presence of several fi sh species and some environmental factors including BOD. The comparison between the periods 2001-2010 and 1991-2000 indicated that the number of fi sh species increased with improvement in river water quality.