Effects of Growth on Polychaete Rockworm, Marphysa sanguinea Integrated Culture with Olive Flounder, Paralichythys olivaceus in Flow Through System

Three experiments were designed to determine the appropriate size and density for optimum growth and survival of rockworm polychaete Marphysa sanguinea integrated culture with olive flounder Paralichythys olivaceus in the flowthrough system under controlled laboratory condition over a 13-week period. The experimental design in T1, T2, T3, T4 and T5 for Experiment-1(<0.5 g) was 200, 400, 800, 400 and 400 worms for Experiment-2 (<0.5-1.5 g) was 100, 200, 400, 200 and 200 worms and for Experiment-3 (1.5-2.5 g) was 50, 100, 200, 100 and 100 worms respectively. The worm feed of T1, T2 and T3 was feces of fish and uneaten feed; that of T4 was controlled-no feed and that of T5 was commercial feed. The polychaete worms were kept in 15 boxes (L50 × W40 × H30 cm), and bottoms of the boxes were filled with a 15~20 cm layer of substrate sediment with 50% gravel and 50% oyster shell. Thirty fishes were placed in each cubic tank (L70 × W40 × H20 cm) with 55 L water. The weight gain of rockworms (<0.5 g) in T1, T2 and T3 for Experiment-1 (<0.5 g) has shown 152.7%, 153.8%, and 140.3%, respectively. The weight gain was higher than in the other two groups, as the weight gain of rockworms in T1, T2 and T3 for Experiment-2 (0.5-1.5 g) was 51%, 30%, and 46%, respectively, and that of rockworms for Experiment-3 (<1.5-2.5 g), that is, 75%, 73% and 62%, respectively. From this result, it can be concluded that in the flow through system a small size (< 0.5 g) group of rockworms can be one of the most suitable species at the density of 2000-4000 inds.m on fish feces and uneaten feed, as they can grow better than 0.5-1.5 g and 1.5-2.5 g rockworms. On the other hand, integrated results have indicated that in the flow through system around 8 g olive flounder fish was an excellent candidate to be associated with 0.5-1.5 g worms, which can grow better than a small size (< 0.5 g) group of rockworms and then 1.5-2.5 g worms at the optimum density 1000-2000 indv.m-2 polychaetes