Bull. Jpn. Soc. Fish. Oceanogr. 74(1), Page 20-32, 2010   Stocking efficiency of juvenile abalones, Haliotis discus discus and H. gigantea, on the coast of Kuzaki, Mie Taisuke Takenouchi1, Hirokazu Matsuda2†, Hideto Tokuzawa3 and Takashi Yamakawa4 1 Fisheries Resources Office, Department of Agriculture, Fisheries, Commerce and Industry, Mie Prefectural Government, Koumeicho, Tsu, Mie 514-8570, Japan 2 Mie Prefecture Fisheries Research Institute, Hamajima, Shima, Mie 517-0404, Japan 3 Mie Fish Farming Center, Hamajima, Shima, Mie 517-0404, Japan 4 Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8657, Japan † matsuh07@pref.mie.jp Twelve groups of juvenile abalones of each Haliotis discus discus and H. gigantea were released in three fishing grounds (Yoroizaki, Nagama and Aramishita) off Kuzaki, Toba City, from 1992 to 2003 to examine the effects of species, release season and fishing ground on recapture rate and economic efficiency. To estimate the stocking efficiency exactly, release of juveniles in each fishing ground was conducted every three years. Four groups released and recaptured in the same fishing ground were easily separated from each other by using the analysis of shell length frequency data sets because the peak in the distribution of shell length for each group was obviously observed. The abalones were recaptured 2-7 years after release by Ama divers. As a trend, recapture rate of H. gigantea (mean=5.5%) was higher than that of H. discus discus (mean=3.5%), although not significant (Mann-Whitney U-test). Mean recapture rates of groups released in spring (3.8% for H. discus discus and 3.5% for H. gigantea) tended to be higher than those of groups released in fall/winter (0.7% for H. discus discus and 2.5% for H. gigantea), but also not significant (t-test). Recapture rate and economic efficiency for abalones released in the Nagama fishing ground were significantly higher than those in the other grounds both for H. discus discus and H. gigantea (ANOVA). Mean economic efficiency indices for the releases of juveniles were 1.4 and 1.8 for H. discus discus and H. gigantea, respectively, showing that release of juveniles is economically efficient. The present study indicates that choices of species, release time and fishing ground are important for effective release of juvenile abalones. Key words: abalone, economic efficiency, Haliotis discus discus, Haliotis gigantea, recapture rate