Abstract
The effectiveness of construction of an artificial spawning channel to enhance white-spotted charr (Salvelinus leucomaenis) and masu salmon (Oncorhynchus masou masou) was examined in a channel (approximately 270 m long and 1 m wide) constructed below an erosion control dam, in the Gamata River, Jinzu River system, Gifu Prefecture from 2005 to 2007. Eight and 15 artificial spawning grounds were constructed in the channel in 2005 and 2006, respectively. As a result, multiple spawnings of the charr were observed at 4 of 8 grounds in 2005 and 8 of 15 grounds in 2006, respectively. The number of spawned eggs and the percentage of eyed eggs were 2503 and 90.0% in 2005. A lot of underyearling charr were observed in April of both 2006 and 2007. The growth, density, standing stock and survival rate of the underyearlings were studied from July to October in both years. The average fork length and body weight in October were 86.0 mm and 8.00 g for the 2005 year-class and 80.2 mm and 6.31 g for the 2006 year-class, respectively. The density and standing stock in October were 0.29 fish/m2 and 2.32 g/m2 for the 2005 year-class and 0.75 fish/m2 and 4.73 g/m2 for the 2006 year-class, respectively. The survival rate of the 2005 year-class was 3.2% from the spawned eggs to the underyearlings of October. The underyearlings were observed near the spawning redds in April, after that they dispersed throughout the channel. No spawning of masu salmon was observed throughout the channel in both years. The results suggest that the construction of artificial spawning channel is effective for the enhancement of white-spotted charr.
