Freshwater aquaculture

Unit 3 - Nursery, Rearing and grow-out ponds

3.2.3. Control of Aquatic Weeds
Large earthen ponds are usually infested with submerged, emergent floating and marginal weeds.
Weeds cause several problems in fish ponds

• They compete for nutrients with phytoplankton thereby reducing the natural productivity fo the ponds.
• Prevent light penetration and suppress the production of phytoplankton
• Cause oxygen super saturation during day and oxygen deficiency during night
• Harbor aquatic insects and predatory fish
• Hinder free movement of fish and reduce their living space
• Cause problems during harvesting by hindering netting operations.
• Increase siltation in the pond, reducing pond depth over a period of time

Therefore growth of aquatic weeds needs to be controlled and their density reduced in fish ponds
Aquatic weeds can be controlled by employing methods such as

• Manual
• Mechanical
• Chemical and
• Biological

The method selected depends on factors such as

• Pond size
• Extent of weed infestation
• Time available
• Cost