Abstract
This study aims at clarifying the relations of habitat conditions required for Pungitius pungitius to the environmental factors of springs in non-irrigation period and at considering with the way of spring management desirable for conservation of the fish populations. The study was conducted in five springs in Hataya, Senhata Town, Akita Prefecture, from December 1997 to April 1998. In those springs, the population density of P. pungitius decreased from December to March, when the amount of eruption water decreased. Particularly distinct decrease in the population density of fry was observed in the springs where the average water temperature in December showed a larger temperature balance between at the eruption point and at other measuring points in the spring. Even in the spring with a smaller value of the temperature balance throughout the investigation period, the lower population density was also observed where the vegetation coverage of aquatic plants was small. In the springs with small fluctuations in the water temperature and high coverage of aquatic plants, occurred the higher population density of fry and distinct rise of the total population density during March through April. In order to avoid the affects of farm land consolidation on the fish population, it is desirable to make connect, via ditches, springs being capable of drying up or having large water temperature fluctuation with those having much amount of eruption and less water temperature fluctuation.
