Title Early life history of ayu in coastal waters
Authers Tsuguo OTAKE
Keywords amphidromous ayu, land-locked ayu, migration history, growth
Citation Bull. Fish. Res. Agen. supplement No. 5, 179-185, 2006
We examined the distribution, age, growth, and feeding of ayu larvae and juveniles in the coastal waters around the mouth of Miya River, Mie prefecture, Japan. The larvae and juveniles were also genetically distinguished between amphidromous and landlocked Lake Biwa forms to determine the possibility of recruitment of larvae originated from stocked Lake Biwa ayu. After drifting into the sea, the larvae shifted their distribution from the coastal areas near the river mouth to the surf zone as they developed into the white-bait larval stage (20mm, 30 days old). They subsequently occurred in the estuary after they reached 30-40mm(90-130 days old), and then they began their upstream migration. The earlier born and larger size juveniles tended to go upstream earlier in spring. The ayu juveniles fed mainly on copepods such as Paracalanus spp., Acartia spp., etc. which were major components of zooplankton fauna of the research area. DNA analysis of ayu larvae and juveniles clearly suggested the mortality of ayu larvae with Lake-Biwa genes just after drifting into the sea.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull-b5/31.pdf