Composite Fish Culture

Fishes Used in Composite Fish Culture

All over the world, the major cultivable fishes especially for polyculture belong to the carp family. There are three major systems of carp culture in the world. They are:

1. Chinese system: - The Chinese carps are cultured together. These are silver carp - Hypophthalamichthys molitrix, grass carp - Ctenopharyngodon idella and common carp - Cyprinus carpio. These are also called as Exotic Fishes in India.
2. Indian system: - The Indian carps are cultured together and are also cultured with Chinese carps. These carps are rohu – Labeo rohita, catla - Catla catla and mrigal - Cirrhinus mrigala.
3. European system: - The main species cultured is the common carp - Cyprinus carpio.

• Other Chinese carps used for composite fish culture:
• Bighead carp - Aristichthys nobilis, Mud carp - Cirrhinus molitorella and Black carp - Mylopharyngodon piceus
• The predatory catfish and murrels can also be incorporated in the composite fish culture system. However, catfish and murrels should be stocked only after the carp species have grown to a considerable size.
• The trash fish and the young of common carp if any, in the culture pond would serve as a good source of food for catfish and murrels.
• The Fringe-lipped carp and the Milk fish are commonly cultured in the composite fish culture in brackish water culture system.
• The air-breathing fishes like murrels, catfishes and koi are also cultured together in the freshwater culture system.

Stocking Densities and Stocking Ratio

• Generally fish production increases with the increase in the stocking density per unit area.
• There is always an optimum stocking rate in a particular situation, which gives the highest production with big sized fish.
• Under crowded condition at a higher stocking density fish may compete severely for food and thus suffer stress due to aggressive interaction.
• Fishes under stress eat less and grow slowly.
• By increasing the stocking density beyond the optimum rate the total demand for oxygen increases with obvious dangers. But, no increase of the total yield of the fish is obtained.
• Stocking density and stocking ratio of fishes should be on the basis of the quantity of water and the amount of oxygen production.
• The above six varieties of Indian and Chinese major carps should be stocked at a rate of 5000 fingerlings of 75-100 mm size/ha.

Percentage of Stocking Density of Fishes:

1. Catla and silver carp : 30 - 35 %
2. Rohu : 15 - 20 %
3. Mrigal and common carp : 45 %
4. Grass carp : 5 - 10 %

• In 5 - species combination excluding grass carp, the optimal stocking ratios are catla 6(30%) : Rohu 3(15%) : Mrigal 5(25%) : Common carp 4(20%) : Silver carp 2(10%).
• In 4 - species combination excluding silver carp and grass carp, the optimal stocking ratios are - catla 6 (30%): rohu 3 (15%): mrigal 6(30%): common carp 5(25%).
• In 3 - species combination excluding exotic carps, the optimal ratios are - catla 4 (40%) : rohu 3 (30%) : mrigal 3 (30%).
• In 8 - species combination is also possible for composite fish culture, where milk fish and fringe-lipped carps are included in the culture system along with Indian and Chinese major carps. But the growth of the additions is not satisfactory