An inundated Salix stand provides spawning and nursery habitat for native fish in a periodically flooded reservoir zone
Azami, Kazuhiro; Higuchi, Takaya; Konishi, Chisato; Hashimoto, Hitomi; Osugi, Tomonori; Asaedea, Takashi; Nakai, Katsuki
The water level in the Miharu Dam reservoir (northeastern Japan) is drawn down to 8 m during the flooding season (4 months on average per year), exposing a section of emergent shoreline termed the "drawdown zone." Over many years of periodic water-level control, Salix species (willows) have established dominant stands in this zone. Salix species are typical inundation-tolerant plant species found on reservoir shores, especially behind dams subjected to water-level regulation. Thus, Salix stands are inundated or emergent for several consecutive months in each year. We aimed to determine whether inundated Salix stands in the drawdown zone provide a native fish (silver crucian carp, Carassius auratus langsdorfii) with spawning and nursery habitats. We tracked three tagged silver crucian carp telemetrically in the front reservoir behind the Miharu Dam. The fish spent considerable periods of time during the spawning season in inundated Salix stands. Over 3 months of field observations, we observed spawning events, eggs, and juvenile carp in the inundated Salix, whereas areas without submerged vegetation did not support spawning or offspring. Thus, this fish species uses flooded Salix stands as spawning grounds and juvenile habitat.