Effects of coexisting Ulva pertusa on the production of kuruma prawn [Penaeus japonicus]

(DGR) of the prawns was calculated using the formula of Deshimaru and Shigeno.5) DGR of U. pertusa was also calculated using the same formula, but expressed as a weekly average. Results showed that prawns cultured with U. pertusa have better production, survival rate, and feed coefficient than those cultured without the alga (Table 1). The production of prawns cultured with U. pertusa in Exp-1 and Exp-2 were 69% and 54% higher respectively than those cultured without U. pertusa. The survival rate of prawns cultured with U. pertusa in Exp-1 and Exp-2 were 67% and 21% higher respectively than those cultured without U. pertusa. The feed coefficient of prawns cultured with U. pertusa in Exp-1 and Exp-2 were 61% and 43% higher respectively than those cultured without U. pertusa. The plant-animal production ratio was found to be nearly the same in both experiments. The present study suggests that the coexistence of U. pertusa in the prawn culture system increased the production and survival of the prawn. The presence of U. pertusa is able to support a better condition of the culture system.