Growth of Batillus cornutusby Capture-Recapture Method

The amount of Batillus cornutus captured in Jeju Island was about 2,000 tons/year for three years after 2000. The mean size of B. cornutus by shell height was 7.7 cm in 2001, 7.9 cm in 2002, and 8.1 cm in 2003. Local mean size of B. cornutus by shell height was 8.7 cm in eastern waters, 7.4 cm in western waters, 7.8 cm in southern waters, and 7.7 cm in northern waters of Jeju Island. To investigate the effect of the growth pattern, an experiment was conducted: the samples were tagged and released in southern coastal waters of Jeju Island on 2nd April (a release test) and 29th October (a recapture test) in 2003. The release stations were two sites, natural reef and artificial reef, where their environmental conditions were different from each other. In April, the size of B. cornutus released in the natural reef was 6.2 cm in mean shell height, and 58.9 g in mean shell weight. The size of B. cornutus released in the artificial reef was 6.6 cm in mean shell height, and 65.9 g in mean shell weight. During the release period, most of B. cornutus were not moved much (less than 10 m) from the original release sites. When B. cornutus was recaptured in October after 7 months, the size of B. cornutus released in the natural reef became 7.4 cm in mean shell height, and 89.4 g in mean shell weight. The size of B. cornutus released in the artificial reef became 7.2 cm in mean shell height, and 84.9 g in mean shell weight. This indicates that the growth rate of B. cornutus released in the natural reef was higher than that of B. cornutus in the artificial reef. These differences in the growth of B. cornutus between study sites were ascribed to the abundance of marine algae grazed by immobile B. cornutus. Namely, with relatively high growth rate of B. cornutus in the natural reef, the number of species (23 species) and biomass (26,703.4 g) of algae were more diverse and abundant than those (7 species and 17,018.4 g) of algae in the artificial reef. The growth of B. cornutus in the natural reef was also correlated to high water temperature (15.5-25.9℃).