Title Estimation of population number of ayu in the Nezugaseki River
Authers Kazuo UCHIDA, Akio SHIMIZU, Shin-ichiro ABE, Toshihiko SATO, Kazuhiko KATSURA and Hiroyuki SAKANO
Keywords ayu, population number, line transect, stock enhancement
Citation Bull. Fish. Res. Agen. supplement No. 5, 197-201, 2006
In 2001~2003 population numbers of ayu were estimated by direct underwater counting with a line transect method from April to December in the Nezugaseki River. Ayu migrated upstream from the sea into the river on May to June in 2001 2003. The maximum numbers of ayu in the river were estimated as 70,000, 105,00 and 27,000 individuals, respectively, and the fish survived 11-18% on October and then spawned. In 2003 a mark-recapture test revealed that the hatcheryreared ayu released in the Nezugaseki River showed similar survival and growth to wild ayu stock.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull-b5/33.pdf