Effect of flooding on fish assemblages in small streams in South Korea

The impact of Typhoon-Rusa-generated flood on fish assemblages was investigated in small streams in the northeastern part of South Korea. As a result of high precipitation (870 mm day(-1)) during the typhoon, stream morphology and substrate composition changed. Stream depth and width decreased and slightly enlarged, respectively. Substantial amounts of mud and silt flowed into the streams and modified substrate composition to a simple state. Although the total number of individual fish significantly decreased after the flood, the dominant species remained the same relative to before the typhoon, and their relative abundance subsequently increased. However, the rank order of fish assemblages before and after the flood changed. Three years after the flood, fish assemblage recovered, but the number of individuals per site was still lower than prior to the flood. Flooding affects fish assemblages both directly and indirectly. Indirect impacts, such as habitat alteration, more critically affected the change in local fish assemblage and delayed recovery time. Nonetheless, fish assemblages persisted at sites where floods occurred.