PROBLEM TO BE SOLVED: To maintain levels of a proliferative effect of a prey creature, and a swarming effect and a proliferative effect of an aquatic organism at certain constant levels or more over a long period of time, thereby contributing to the fishing industry.SOLUTION: A method for replacing a prey creature proliferative reef 11 that includes four substrate material units 13 formed by prey creature proliferative substrate materials 16 being accommodated in a cage-like body 17, and a base 15 where the four substrate material units 13 are disposed, and is immersed on a sea bottom 12 in large numbers includes: a lifting step for lifting old prey creature proliferative reefs 11 that are immersed, by a vessel 25； a replacing step for replacing old substrate material units 13 removably attached to the old prey creature proliferative reefs 11 lifted on the vessel 25 with new substrate material units 13； and an immersing step for immersing the new prey creature proliferative reefs 11 with the new substrate material units 13 on the sea bottom 12, etc.
