An overwintering ground for fish in a fish-retreat ditch created in a paddy irrigation and drainage system near the sea.

Abstract

The importance of biodiversity conservation in paddy field ecosystems is widely recognised, as is the importance of maintaining a water body in the paddy field throughout the year. This study monitors the ascending and descending of a fish community in a fish-retreat ditch constructed in a paddy field near the sea in Kunitomi District, Obama, Fukui Prefecture, Japan. The fish-retreat ditch is not only a spawning ground but also an overwintering ground for Misgurnus anguillicaudatus and Cobitis sp. BIWAE type A (pure freshwater fish). The fish-retreat ditch will be not only a growing ground but also an overwintering ground for Tribolodon hakonensis, Gymnogobius urotaenia (amphidromous fish) and Acanthogobius flavimanus (brackish water / marine fish). It is considered that the fish-retreat ditch, which has less environmental changes than rivers, drainage canals and oceans, has become a cradle for many fish.