Population density, growth and migration via the sea to different streams of Japanese dace Tribolodon hakonensis in lower reaches of small streams
2010
Katano, Osamu | Nakamura, Tomoyuki | Abe, Shin'ichirō | Baba, Yoshihiro
Ecological characteristics of Japanese dace Tribolodon hakonensis were investigated in three small streams in Niigata Prefecture from 2001 to 2005 with special reference to the effect of Ayu Plecoglossus altivelis altivelis on the dace. Japanese dace were distributed in short sections below dams near the mouth of the streams flowing into the Sea of Japan. In this section, Ayu were numerically dominant from June to August, and the growth rate of dace in this period was negatively correlated with the density of Ayu. The population density of dace was high in October, but some adults stayed in the streams in June and August. When data for the five years were combined, the density of dace was negatively correlated with that of Ayu in two of the three streams. The increase in density of dace in October is considered to be due to the migration of dace from the sea. Eight dace were confirmed to migrate to different streams via the sea. Therefore, the life history of Japanese dace in the study region contained considerable individual variation.
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