Growth of the abalone Haliotis diversicolor (Reeve) fed with macroalgae in floating net cage and plastic tank

The abalone Haliotis diversicolor (Reeve) or 'tokobushi' is being cultured in Kagoshima, southern Japan for stock enhancement of fishing grounds. However, with decreasing catches from the wild some fishermen's group may eventually resort to rearing tokobushi until of marketable size. Growth experiments of tokobushi fed macroalgae in floating net cage and plastic tanks were conducted to evaluate the influence of culture system, macroalgal food, age and water temperature on their culture. In floating net cage, marketable sizes were obtained at the age of 457-822-day old (15-27-month old) with highest growth rate of 2.36% g day(-1) and 0.21 mm day(-1). One advantage of the plastic tank culture system was that the tokobushi shell remained clean throughout the culture period. Macroalgal food affected the growth rate; Sargassum fusiforme (Setchell)- and Ulva pertusa (Kjellman)-fed tokobushi were better than Meristotheca papulosa (Montagne)-fed. Further, 1-year-old tokobushi had better growth performance and condition index than the 2-year-old cohort, and growth rates were higher at 17 degrees C than at 12 degrees C. These findings should help tokobushi farmers design their mariculture scheme considering both economic and environmental aspects.