The author distinguishes between 'ocean fish farming' and 'ocean ranching'. The distinguishing characteristic of ocean ranching is that the released species are unassisted once released into the ocean. Ocean ranching in turn is classified as' pure ocean ranching' (animals intended to be harvested by the entity that released them) and 'stock enhancement ocean ranching'. The document first relates the experiences in ocean ranching in Japan, the United States and Iceland up to the mid-1990s. It then describes the fundamental externality of ocean ranching and finally discusses methodologies for assessing the costs and benefits of ocean ranching.