Abstract
Habitat selection and food habit of a goby fish, Rhinogobius sp. OR “Shimahire gata” were studied in relation to habitat and microhabitat structure of “Wando”, lentic water bodies formed along river banks, in the lower reaches of Yodo River, Japan from August 2001 to June 2002. The goby fish inhabited exclusively in Wando and none of the fish were found in the main channel. The fish density was more in Wando which were far from main channel than Wando connecting with main channel through a year. The distribution pattern agreed with the microhabitat preference of the fish to muddy and litter-rich substrata which were not preferred by other Rhinogobius fish. Gut contents of the fish particularly of juveniles were more in May than in other seasons. The gut contents were composed mainly zooplankton such as Cyclopidae gen. spp. and Alona spp. and benthos such as Chironomidae and Micronecta sp., most of which were typical still water inhabitants. These results showed that Rhinogobius sp. OR adapted to the lentic water condition of Wando. However, the fish used underside of unembedded stones for spawning bed in a newly constructed Wando. The density of adult fish increased in the newly constructed Wando in the breeding season and their larvae and juveniles stayed there in the growing season. It was suggested that the goby fish requires both depositional still water habitats for feeding and erosional stony habitats for spawning. Influence of the floodgate operation on environmental conditions and goby fish populations in Yodo River was discussed.
