Stocking efficiency of juvenile abalones, Haliotis discus discus and H. gigantea, on the coast of Kuzaki, Mie [Japan]
2010
Takenouchi, T., Mie-ken. Government Office, Tsu (Japan) | Matsuda, H. | Tokuzawa, H. | Yamakawa, T.
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.
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