Migration of wild and cultivated juvenile honmoroko Gnathopogon caerulescens of from the spawning and nursery areas in Lake Biwa were investigated, both in the Ibanaiko Lagoon and its outlet to Daido River, using beam-trawl surveys in 2013 and 2014. The study demonstrated migration of G. caerulescens from a nursery lagoon toward Lake Biwa after the juvenile stage. These findings appear to be the first direct evidence for migration of an exclusively pelagic cyprinid species from a littoral nursery to a pelagic adult habitat in a large deep lake.

Op s a r i i c h t h y s u n c i r o s t r i s が死亡していた。 ハスを滋賀県水産試験場に持ち帰って検査したところ， 鰓に繊毛虫の一種である Ch i l o d o n e l l a h e x a s t i c h aの大量 寄生がみられた。日本国内では，飼育水槽内において ディスカス Sy mp h y s o d o n d i s c u s に寄生した事例が唯一 のものである（I ma i e t a l . , 1 9 8 5 ） 。本報では C. h e x a s t i c h a

Otolith growth increments in wild‐caught alizarin complex one (ALC)‐marked honmoroko Gnathopogon caerulescens were examined to verify the veracity of the age determination method in cyprinids. ALC‐marked G. caerulescens recaptured from their natural environment had lapilli increment counts outside the ALC ring mark that had formed on a daily basis during the juvenile stage. This apparently being the first direct evidence of daily periodicity of otolith increment formation in wild‐caught cyprinids.

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