A STUDY ON THE POLYCULTURE OF SEA Squirt Halocynthia roretzi AND SEA CUCUMBER Apostichopus japonicas UNDER A HANGING CULTURE SYSTEM
The southern part of the Korean sea is an important aquaculture ground because of its mind water temperature and many islands around that protect typhoons and strong waving waves. However, the changes in the natural environment and high-density cultures in a limited area have hampered productivity while caused mass mortality of species. This calls on us to develop eco-friendly farming technology so as to achieve sustainable aquaculture farms. To that end, it is necessary to develop aquaculture technology which not only helps the vertical use of sea surface and bottom but also improves environment in the sea cucumber poly culture. It is also necessary to develop poly-culture technology for oysters and sea squirt, the two major filtration-feeding culture species in the South coast and sea cucumber, a high valude-added species functioning as a cleaner.
The average size of young sea cucumber released in April was 3.7 ± 2.9 g. It continued to grow during the summer season and grew to an average of 9.1 ± 3.0 g in December. The average size of adult sea cucumber released in April was 31.5 ± 5.6 g in April. It became smaller to 20.8 ± 5.9 g in early summer but grew back to 28.8 ± 13.8 g in December. It has been confirmed that heavier sea cucumbers are more affected by high water temperature, so they sleep in the summer. Most of the sea cucumber were found to be under a shelter. From our night time survey on September 10, 2016, they were found out of the shelter. The density of sea cucumber had decreased to 4.2 individuals/m2 until July since they were released from the shelter of the farms. Since then, it slowly decreased to be 3 individuals / m2 in December. The survival rate of each shelter is 28.0% for A >, 27.2% for B > 19.7% for C type,