Brief review on ecosystem models is carried out which begins with Riley (1949) up to recent representative numerical models. Review of my own researches follows after that. Early works are mainly on primitive three dimensional physical-ecological coupled models and also dealt with assessment of aquaculture. Recent works on NEMURO project are reviewed in detail.

Observational data in the regular sections over 39 years (1967-2005) which have been performed by the Iwate Fisheries Technology Center are used to investigate long-term variabilities of temperature and salinity fields in the upper ocean of the Sanriku Coast. The leading EOF modes calculated from 1-year running mean time series to remove variations with periods of 1 year which are dominant in the monthly temperature and salinity fields, have a contribution ratio exceeding 70% and the same sign over the entire domain. The amplitudes are highest in the subsurface layer of the of-shore region for the temperature and in the near-surface layer of the of-shore region for the salinity field. The time variations are characterized by rapid depressions in the first half of the 1980's both in the temperature and salinity fields and in the last half of the 1990's only in the salinity field. The differences between two 5-year mean fields prior and subsequent to the shifts exhibit that the cooilng and freshening in the former case (1980's) are dominant in the subsurface layer of the of-shore region and have a high correlation with the southern limit latitude of Oyashio Water, suggesting a relationship with a large-scale variation. On the other hand, the salinity depression in the latter case (1990's) is dominant in the near-surface layer of the on-shore region, suggesting that it is caused by a change of fresh water flux through the sea surface.

The characteristic behavior of surface water with low salinity and high chlorophyll a concentration in the head of Ariake Bay, was elucidated by intensive field observations using CTD, drifting buoys, HF radars and satellite images. Such surface water mass has only 1 m thickness and has a different divergence/convergence character from that in the lower layer. Such a divergence/convergence character has a close relation to the chlorophyll a concentration, that is, the high chlorophyll a concentration area coincides with the surface convergence area.