Effects of Pom-nang Seaweed, Gracilaria fisheri on Growth, Survival, Feed Efficiency and Catalase Production of Juvenile Mud Crab, Scylla paramamosain

Abstract

The study on the effects of Pom-nang seaweed, Gracilaria fisheri on growth, survival, feed efficiency and catalase production of juvenile mud crab, Scylla paramamosain was conducted. The main objectives of this study are to investigate (1) effect of dietary diets with different Pom-nang seaweed supplementation’s levels on growth rate, survival rate, feed efficiency and catalase activity of juvenile mud crab and (2) influence of Pom-nang seaweed density as a shelter and stocking density on growth, feed efficiency, and survival rates of juvenile mud crab. Two experiments were conducted. The first experiment, juvenile mud crabs were individually stocked in plastic containers with an initial body weight of 0.02 g. Two factors including five dietary treatments (Pom-nang seaweed powder supplemented at the level of 0%, 2%, 4% and 6% and control; mysid shrimp) and two shelter treatments (with Pom-nang seaweed as shelter and without shelter) were designed. Juvenile mud crabs were fed at 8% body weight for 28 days. It was found that different diets had significant effects on weight gain (WG), specific growth rate on body weight (SGRw), protein efficiency ratio (PER) but not for feed conversion ratio (FCR), catalase activity (CAT) and survival rate of the crabs. The crabs reared with seaweeds as shelter had significantly different PER, FCR, CAT and survival rate values compared to those without seaweeds as shelter (P < 0.05). There were significant differences on the interactions of the combined factor on WG, SGR and PER (P <0.05). It was found that mysid shrimp was the most appropriate food for nursing juvenile mud crab. However, formulated diets supplemented with seaweeds had a potential to replace mysid shrimp. The combination of seaweed as shelter and the formulated diets with 4% seaweed (PSP4) had the highest values of all growth performances and survival rate compared to the others. The second experiment, effect of stocking density and density of Pom-nang seaweed as shelter on growth and survival rates of juvenile mud crab were conducted using juvenile mud crab with an initial body weight of 0.02 g. Two factors including four stocking density treatments (100, 200, 300 and 400 crab/m2) and four densities of Pom-nang seaweed as shelter (100 g/m2, 500 g/m2, 1,000 g/m2 and without shelter) were tested. Juvenile mud crabs were fed with PSP4 at 8% body weight for 28 days. It was found that different stocking density had significant effects on PER and FCR (P <0.05), and different density of Pom-nang seaweed as a shelter had significant effects on PER, FCR and survival rate (P <0.05). The stocking density at 400 crab/m2 and high density of Pom-nang seaweed as a shelter at 1,000 g/m2 was the optimal rate for nursing juvenile mud crab as indicated by growth performances and survival rate. There was no impact of interaction effect of the combined factor. This study can support a new technique and method for the development of nursing mud crab in the future.