1Tamano Station, Japan Sea-Farming Association, Tamano, Okayama 706-0002, 2Fisheries Experimental Station, Okayama Prefecture, Ushimado, Okayama 701-4303, 3Okayama Prefecture Office Fisheries Division, Okayama, Okayama 700-8570, Japan
To develop an artificial nursery reef for stocked red spotted grouper Epinephelus akaara juveniles, a release experiment was carried out using artificial reefs which contained mesh pipes each with a string of scallop shells. We used two diflerent methods of spacing the scallop shells, the spacer type (3 cm long plastic tubes between each shell) and the non-spacer type. Three reefs of each type were installed on the bottom ofl Shiraishi Island, central Seto Inland Sea in July 2000. One thousand red spotted grouper juveniles were released into each experimental reef (total number 6,000) in October 2000. Underwater observations and salvage operations were conducted several times to estimate the number of residual fish and their foraging activity over about one year after release. These observations indicated that both types of the experimental reef provided shelter and had a food organism propagation function for the released fish. The number of residual fish were generally larger in the spacer type reef. A reef with appropriate spacing will be suitable as a nursery reef for released juvenile red spotted grouper.