Freshwater aquaculture

Unit 6 - Sewage Fed Fish Culture

6.4. Sewage fed fish culture of West Bengal

• As stated earlier, West Bengal is the only state in India where raw sewage is used for fish culture.
• The sewage fed fish culture is carried out in Bheries where raw sewage from Kolkata city is let into the Berries in small quantities at monthly intervals.
• In small Bheries fish and paddy are grown alternately while in bigger Bheries only fish is grown. The sewage is let into the ponds to a depth of 90 cm along with tidal water in a ratio of 1:4, sewage to water. The water is allowed to settle for 15-20 days after which it becomes clear and odourless. Subsequently plankton will grow in the Bheries. The ponds are then stocked with fingerlings of Indian major carps of size 7.5 – 15 cm in the month of April. Some farmers also stock silver carp and common carp. Harvesting begins in September and ends in February. The weight of the stocked fish is about 500-550 kg/ha and the final yield from this system is about 3000 kg/ha/year.
• Tilapia can also be grown in sewage fed ponds since they are capable of tolerating poor water quality prevalent in sewage fed ponds and production of up to 9000 kg/ha/yr of 70-200 mm Tilapia can be obtained.
• Raw sewage has the potential to cause human health hazard. Therefore only treated sewage should be used for fish culture.
• Other countries such as Far East, Middle East, Germany, Hungary and Israel use treated sewage for fish culture.