Reconstruction Support and Planning for Fishery in Brackish Water Area

Representative Organization: Tohoku University

2017/04/01 - 2018/03/31
Monthly

The Natori River estuary in Miyagi Prefecture

Field survey

The surveys have been proceeding to clear the status of fishery resources and environmental conditions in the Natori River estuary and support the construction for the fishery. 1. Monitoring of physical environments (Salinity, Temperature, Depth and Bottom sediments) 2. The survey on the Manila clam population status(population density , size composition) 3. The survey on the Brackish water clam population status (population density , size composition) 4. The survey on the Ayu population status.

Brackish water clam (Corbicula japonica) Brackish water clam abundance has returned to approximately the same levels as before the tsunami, but with an upstream shift in the C. japonica habitat of about 1 km due to movement of the brackish water zone. Ayu (Plecoglossus altivelis altivelis) The CPUE of ayu in 2011 is the lowest in past years. The residual upstream ayu population seems to have grown successfully and reproduced despite the effects of the tsunami, one year after the tsunami occurred, the ayu population had recovered to the same level as before the event. Manila clam (Ruditapes philippinarum) Manila clam recruitment has not yet occurred successfully since the tsunami. In 2015, the research indicated no mass reduction of the Manila clam, and spring -spawned juveniles grew normally from May to August. The data logger recorded normal range in salinity fluctuating on tidal rhythms. It is suggested the steady inflow of seawater is affecting the habitat condition of the Manila clam.

FY2017 Reconstruction Support and Planning for Fishery in Brackish Water Area

Water temperature and salinity in the Natori River Estuary (FY2017)
CPUE of ayu population in The Natori River
Distribution of manila clam