Reproduction is controlled artificially, and the cost is shared by the government and beneficiaries similar to the set-net fisheries. All of the spawning fish are caught, and there is no escapement for natural reproduction or the sport fishery. It is an important question as to what phase our society should support for masu salmon resources. Actually, there is no choice. The development of rivers for flood control or water supply to big industries is continuing.
Japan is presently in the second phase in Hokkaido and the final phase in Honshu Island.
The ability to propagate artificially has been one of the conditions for which permission has been granted to develop rivers. The development of rivers has been one of the reasons that artificial propagation was needed. It is a vicious circle. Throughout this process, replacement has been continuing. It has become difficult to preserve the natural stocks.