Settlement, growth and survival of abalone, Haliotis discus hannai, in response to eight monospecific benthic diatoms

The settlement, early growth and survival of the larval abalone Haliotis discus hannai in response to eight monospecific benthic diatoms were examined in the laboratory. Postlarvae showed active settling and feeding behaviour in all diatom species and in naturally occurring diatoms. Larval settlement rates differed significantly between experimental substrata after 24 h and 48 h. Nitzschia sp. (96.67 %), Hantzschia amphioxys var. leptocephala (95.00 %) and Navicula seminulum (90.00 %) strongly induced larval settlement of H. discus hannai. Postlarvae could feed on benthic diatoms (< 36 μm in shell length) with both weak and strong adhesion on the 4th day after settlement. Greatest growth (shell length) occurred on Nitzschia sp. (786.84 μm ± 2.50 SE and 773.09 μm ± 2.09 SE). Survival of postlarvae was also greatest on Nitzschia sp. (95.33 % ± 1.45 SE). These results indicate the effectiveness of Nitzschia sp., H. amphioxys var. leptocephala, N. seminulum, Rhaphoneis surirella and Navicula corymbosa as single species over natural diatoms in larval settlement and postlarvae growth of H. discus hannai. Thus, Nitzschia sp. has the best potential diet for larval settlement and postlarvae growth of H. discus hannai. H. amphioxys var. leptocephala and N. seminulum can be used as cues to induce larvae settlement, and R. surirella and N. corymbosa can be used as food for growing postlarval.