Effects of stocking densities and seaweed types as shelters on the survival, growth, and productivity of juvenile mud crabs (Scylla paramamosain)

The effects of utilizing green seaweed (Cladophora sp.) and red seaweed (Gracilaria tenuistipitata) as a shelter in the nursery rearing of juvenile mud crabs (Scylla paramamosain) at different stocking densities were investigated for 3 weeks. The investigation comprised a 3 × 2 factor with three stocking densities (200, 300, and 400 ind/m²) combined with two types of seaweed (green seaweed and red seaweed) randomly allocated in triplicate tanks. Juvenile crabs (0.81 ± 0.09 g) were stocked in 150-L tanks (tank bottom area: 0.3 m²) at a salinity of 15  ppt with constant aeration. Crabs were fed twice daily with frozen Artemia biomass. The findings revealed that the survival and growth rate of crabs did not significantly respond to the combined effects of seaweed type and stocking density (P > 0.05). Crabs reared at a low density (200 ind/m²) grew faster than those reared at a high density (400 ind/m²), while seaweed type did not affect crab growth rates. Moreover, crab production increased noticeably as stocking density increased and was significantly influenced by the interaction. The highest crab production was found in the 400 ind/m² treatment with red seaweed as shelter when compared to other treatments (P < 0.05), indicating that this seaweed species is an ideal shelter for rearing juvenile crabs at high density.