The growth of abalone, Haliotis discus hannai, cultured in a multi-tiered, continuous-flow system (MTCFS), was examined to determine the effects of density and tank position in a MTCFS, from mid June 2007 to the end of March 2008, at the abalone culture facility in Fukushima-chou, southern Hokkaido, Japan. Mean shell length and body weight of abalone at the start were 34mm and 5.3g. After 290 days, they grew to 56.7mm, 53.7mm, and 53.0mm in shell length and, 25.3g, 22.3g, and 20.6g in body weight for the high and low density groups in a MTCFS, and for the cage cultured group, respectively. Density in the cage cultured group was kept at the same density as the high density MTCFS group. Mean shell length and body weight increased most in the low density MTCFS group. At the same density, the weight of abalone cultured in the MTCFS was significantly higher than in the cage cultured group, but the shell length did not significantly differ between the high density group and the cage cultured group. The size of the abalone, 119days into experiment, differed depending on the tank's position in the tiered system. Shell length and body weight were bigger in the upper tanks and smaller in the lower tanks. As more food leavings and feces remained in the lower tanks, water quality was suggested to be the most important factor affecting the growth of abalone in relation to the position of a tank in the multi-tiered continuous-flow system.
