Control or Eradication measures of predatory fishes

a. Netting:

• Conventional method to control unwanted fish.
• Repeated netting by fine meshed drag net ensures successful removal of the wild and predatory fishes to a large extent.

b. Hooks and lines:

• Conventional method and is used for catching mostly the piscivorous fishes like Wallago, Channa, Clarias, etc.
• Consists of hooks which is baited and a line attached to it.
• Sometimes rod and lines are used with live baits.
• Nature of bait, bait size and the size of hook determine the selectivity of the catch.
• Thus, complete removal of unwanted fish is not possible by this method.

c. Draining out and drying the pond:

• Complete dewatering of the pond followed by the drying of bottom mud at least for one week is suggested as a success method in eradication of unwanted fishes.
• This keeps the pond in hygienic condition and kills all the existing fishes.
• If dewatering is not feasible or uneconomical, the pond should be poisoned.

d. Poisoning:

• Sure method of eradicating the wild and predatory fishes from any sized water body.
• Use has been restricted because of its high toxicity effect to the aquatic and sub-aquatic animals.
• Are of 3 types:

I. Poisons of plant origin: Derris root powder, Tea seed cake, Pine sanewar, Kukur tarul, etc.

ii. Organonphosphates: Thiomenton, Phosphamidon, etc.

iii. Chlorinated hydrocarbon: Endrin, Dieldrin, DDT, BHC, etc.

Preventive measures

• Keep screen/filter in the inlet pipe.
• Stock the fishes before the breeding season of wild and predatory fishes.
• Repair the damaged portion of pond dike before rainy season.
• Care should be taken to avoid mixing of wild and predators with cultivated fish seeds.