The first record of spawning-season homing of gin-buna crucian carp Carassius sp. to a lakeside biotope connected to Lake Biwa confirmed via acoustic telemetry and egg surveys.

Gin-buna crucian carp Carassius sp. is a widely distributed cyprinid fish inhabiting lakes and rivers throughout Japan. The species is categorized on the Red List of Shiga Prefecture as a "Species of Concern", given a suspected population decline in Lake Biwa; however, its spawning ecology in the lake is yet to be fully elucidated. Therefore, in this study, we examined the spawning and migratory behavior of gin-buna crucian carp at a lakeside biotope connected to the lake via egg survey and acoustic telemetry. DNA analyses of field-collected eggs showed that gin-buna spawned in the biotope during March–April in 2019 and 2020. Three gin-buna captured in the biotope were tagged with acoustic transmitters and released into the lake in October 2019, and one individual returned to the biotope in March 2020. These results suggest that some individuals of gin-buna use the biotope as a spawning ground for multiple years. [ABSTRACT FROM AUTHOR]