The Japanese abalone “tokobushi” (Haliotis diversicolor Reeve) supports a valuable fishery off Tanegashima Island, southern Japan. However, catches have been declining, probably caused by over harvesting and other factors. Understanding the effects of macroalgal type and water temperature on the consumption rates of tokobushi has applications for the management of its population such as to identify sites with appropriate quality and quantity of macroalgae and the favorable water temperature during stock enhancement. Under controlled conditions, the effects of macroalgal type and water temperature on the macroalgal consumption rates of tokobushi were evaluated. On a short-term basis (24-h feeding), consumption rates were higher on leathery brown algae (Sargassum fusiforme, Sargassum patens, Sargassum duplicatum, Sargassum alternato-pinnatum, Undaria pinnatifida and Laminaria japonica), corticated red algae (Acanthophora spicifera, Gracilaria gigas, Carpopeltis affinis and Ceramium sp.) and foliose green algae (Ulva pertusa and Enteromorpha intestinales) than on siphonous green algae (Codium spp.) and filamentous green algae (Chaetomorpha crassa and Cladophoropsis zollingeri). Averaged across 20 species of macroalgae, the mean consumption rate was 4.96 ± 0.27%wet-TW.d−1 (wet alga and wet abalone; TW = total weight) or 1.37 ± 0.19%dryTW.d−1 (dry alga and dry abalone). On a long-term basis (20 days feeding), tokobushi had higher consumption rates on the green alga Ulva pertusa and the brown alga Sargassum fusiforme than on the red alga Meristotheca papulosa. When presented with a choice of species (3 days feeding), tokobushi ate more of the brown alga Sargassum fusiforme and the red alga Gracilaria gigas than the green alga Codium cylindricum. Consumption rates generally increased with temperature. Generally, tokobushi prefer macroalgae with high percent dry weight composition, most of which are brown and red algae, and eat more at water temperatures around spring/fall (17°C, 21°C) and summer (27°C) in Kagoshima, Japan.
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Vol. 24 • No. 4