Optimization of stocking density of milkfish (Chanos chanos) in polyculture system with seaweed (Gracilaria sp.) on the traditional pond

To determine the optimal stocking in the traditional pond is the objective of this study. The study was carried out from March until June 2019 in Karawang, West Java. The milkfish stocking density is the treatment A: 3 fish/container (2,500 fish/ha); B: 6 fish/container (5,000 fish/ha) and C: 9 fish/container (7,500 fish/ha). The weight of the seaweed planted is 900 g (1 ton/ha) for each treatment. Net as a research container measuring 3 x 3 meters was placed in the middle of the pond. The main variables analyzed were growth rate, absolute weight, daily growth rate, survival, and final weight of milkfish. For seaweed, weight and length gain, absolute weight, and daily growth rate. The observed water quality includes temperature, pH, DO, salinity, and brightness. The results showed that the milkfish density of 3 fish/container gave the highest (p<0.05) of absolute weight 25.43 (±1.75) g, survival rate 88.9 (±1.27) %, and ADG (p>0.05). The lowest weight of seaweed occurred in the treatment of 9 fish/container which is 74.67 g. The optimal number of milkfish stocking in a polyculture system with seaweed is 3 fish/container (2,500 fish/ha).