Artificial Reefs Contribute to Marine Resources Enhancement

Abstract

When there are things such as sunken vessels in sea bottoms, Japanese ancient people knew by experience that various fishes gather near these sunken vessels. The function of sunken vessels is the same as natural reef. Therefore, artificial reefs had been constructed from ancient times as auxiliary fishing gear that aim to gather fishes. At present, artificial reef fishing ground had been constructed to gather, propagate and protect fishes from larval/juvenile stage to adult stage, because fishery resources are observed to be in extreme decrease in their juvenile stages. Depending on the scale of artificial reef fishing ground, in Japan there are the fishing grounds of around 400 cubic meters called 'Namigata-sho', fishing grounds of several thousand cubic meters called 'Oogata-sho', and fishing grounds of more than 30,000 cubic meters called 'Jinkou-sho'. The aim of installing artificial reefs is to expand the natural reefs and create new fishing grounds equal to natural reefs. In addition, there is a new-type of artificial reef which is called 'upwelling mound'. If this new artificial reef can raise rich nutrient salts near the bottom layer into the euphotic zone, artificial reefs will enhance primary productivity of the surrounding sea area, which in turn will raise fishery production capacity as a result. For discussion in this Symposium, two Japanese artificial reef activities will be introduced. The first is artificial reef fishing ground for marine resources enhancement, and the second is measurement method on fish-gathering effect and fish propagation effect around artificial reefs.