A Research on Habitat Condition of Hotoke Loach in “Yatu” Waters

Case study of the upper stream of the Okuri River

Abstract

To extract the environmental factors which influence living of Hotoke loach which is typical fish in Yatu waters, we investigated Hotoke loach's distribution situation, waterway structure, hydraulic factors, and water quality from June, 2004 to November, 2006 in two Yatu Waters in Tokyo.
As a result, the Hotoke loach has a different requirement for the environmental factors at each growth stage. The number of adult fish has srong positively correlation with the water depth when flow decreases and it was suggested that the flow is more restrictive than other factors. Moreover, it was suggested that there is a possibility of elevating the mortality rate for the individual which had finished breeding with the rise of the water temperature.