Proposal of A Self-sustainable Abalone Culture System Based on Kelp Intercalary Growth in Deep-sea Water

Abstract

As a course of multiple/cascade utilization of deep-sea water (DSW, known as a cold, clean and nutrient-rich seawater) pumped from Toyama Bay, a self-sustainable abalone culture system was proposed. In the system, DSW enhances the intercalary growth of kelp after cutting off its blade tip, which is fed to abalone cultured in the warmed drainage of kelp culture. In the present study, Laminaria japonica Areschoug (ca. 50 cm in total length) was reared in outdoor tanks using running intact (3 °C) or warmed DSW (11 °C). Blade tips were cut off at 15 cm above the stipe-blade transition every month to feed the juvenile abalone Nordotis discus hannai (Ino). Growth was examined using a hole punching method from March 2001 to January 2002. All of the pruned kelp continued to grow even after the repeated cut-off by 11 times. The mean elongation varied from 1.3 to 8 cm/week in length, recording the maximum of 16.7 cm/week in March. The cut-off blade tips formed sori in 2 weeks every month when cultured using DSW (11 °C). Juvenile abalones (41mm in shell length) were fed 0.25 g and 0.75 g of blade tip per shell in a day at 15 °C and 18°C, respectively. The pruning method allows us to use shorter culture tanks, to keep high kelp densities without forming canopies, to prevent elongated kelp from deteriorating by exposure to the air, and to utilize all of the produced materials of kelp without wasting. In addition, the sorus formation provides year-round kelp seed production. In the proposed system, a quarter of cultured kelp is rotationally pruned every week to supply sufficient blade tips to abalone. Using the system, 12, 000 to 16, 000 abalones (40 mm in shell length) can be reared by culturing 12, 000 pruned kelps.