Comparison of two types of artificial nursery test reef by experiment of releasing juvenile red spotted grouper Epinephelus akaara under natural conditions [Japanese]

摘要

This study examined the possibility of artificial nursery reef for released red spotted grouper, Epinephelus akaara. Two types of test reefs, nylon brush reef and scallop shell reef, were made and sank offshore of Kama Island, Seto Inland Sea, Japan on 5 August 1999. One thousand artificially reared red spotted grouper (95 mm in TL) were released into each test reef on 9 November 1999. Scuba divers observed and counted the fish in and around the reefs nine times throughout the experimental period. Most parts of the reefs were salvaged on 3 April 2000 (146 days after release) to recapture the resident fish. The total number of recaptured fish was 103 in the nylon brush reef and 204 in the scallop shell reef. This result indicates that the idea of artificial nursery reefs for released grouper is effective. The scallop shell reef is superior to the nylon brush reef, since the former attracted and kept twice as many juveniles as the latter. Sixty-five percent of recaptured fish fed on crustaceans which were commonly found on the reefs. These types of test reefs had a food organism propagation function in conjunction with shelter function.