1950 年 16 巻 4 号 p. 119-126
Cottus pollux Günther cannot live in some parts of Chikuma River on account of the polluted water or lack of the water caused by power plants. Its breeding in this river occurs from early February to the middle May, and the temperature of water during the season stands 4.0-10.5°C at 10 a. m. The eggs are laid under the flat stones in the rapid stream. The number of the eggs one fish contains is in proportion to the body length, and the breeding is done about 3 times during the season. When the body is 10.5 c.m. long on the aw average, it breeds about 300 eggs a time, and the diameter of the eggs laid under the stone is 2.9-3.3 m.m. The color of the eggs is mostly light orange.