瀬戸内海伊吹島におけるキジハタ放流人工種苗と天然当歳魚の生態

概要

論文の詳細を見る
Field observation was conducted for released red-spotted grouper, Epinephelus akaara, at the protected area near Ibuki-jima Island, Kagawa Prefecture to develop effective techniques for stock enhancement of this fish. On Oct. 20 1977, 4,214 hatchery-produced fingerlings were released to the site. Numbers of the fingerlings within a fixed 20 m × 20 m area (quadrat) were counted for 16 days after releasing, and condition factor and stomach content of the fish at the site were also examined. The number of the released fish in the quadrat decreased from 487 on the released day to 17 on the 16th day with daily decreasing rate of 19%, and the value was lower than previous trials at the same site. However, considerable amount of fish were found behind several rocks, suggesting that simple visual observation is not considered to be effective to examine numbers of this fish in the area. Condition factor of the released juveniles was higher than that of the wild fish just after releasing ; however, it sharply decreased to the level of wild one within 4 days. Percentage of the empty stomach of the released juveniles was significantly higher than that of the natural one suggesting that one month and more is required for released juveniles to acclimate to natural environment.
生態工学会の論文
2009-01-31