Effects of Stocking Density and Tank Tier Position on the Growth of Haliotis discus hannai in a Multi‐Tiered Continuous Flow System and an Evaluation of Economic Efficiency

The performance of a multi‐tiered continuous‐flow system (MTCFS) used to cultivate Haliotis discus hannai was evaluated in an industrial‐scale facility, focusing on growth, water quality, and cost–revenue analyses. The system was composed of 10 inclined tiers, allowing efficient solid waste removal via hydraulic forces, and was tested with abalone measuring 20.8 ± 1.4 mm. Growth at stocking densities of 133–1022 individuals m −2 was evaluated over 495 days. The daily shell length increment (DSI) ranged from 36.4 to 53.0 μm day −1 and the daily growth rate (DGR) ranged from 15.1 to 28.7 mg day −1 . The survival rate ranged from 81.6% to 88.0% and remained high even under high‐density conditions. A tank tier position experiment was conducted for 945 days, with abalone evenly arranged in single‐cell units. The DSI was 42.1 μm day −1 in the first tier and 31.3 μm day −1 in the tenth tier. Free ammonia nitrogen (FAN) levels remained below the 5% maximal effective concentration (EC 5 ) of 0.041 mg L −1 in all tiers. In the lower tier, dissolved oxygen (DO) decreased, resulting in periods where the EC 5 threshold (7.36 mg L −1 ) for growth reduction was undershot. Furthermore, comparing DSI, DGR and DO saturation on days 660 and 945 revealed a positive correlation between DO saturation trends and growth. Construction and labour costs accounted for 60.6% of the total aquaculture costs, with electricity costs stable at 12.0% in the industrial‐scale facility. In the profitability analysis for an industrial‐scale operation scenario (100 MTCFS units, three labourers and compound feed), assuming cultivation from 20.8 mm to the harvest size of 60.0 mm, a stocking density of 927.10 individuals m −2 was shown to balance revenue with the costs incurred during the cultivation period. Overall, although growth performance in the MTCFS was partly constrained by reduced DO in the lower tiers, the system was shown to be an effective system for industrial‐scale aquaculture production.