Question

Predatory and weed fishes in the pond can be controlled by

• A. Mahua oil cake
• B. Kerosine
• C. Diesel
• D. Cotton seed cake

Hint:

Mahua oil cake acts as a dual-purpose pond management tool. It serves first as a natural, safe piscicide (due to saponin), and later decomposes into a nutrient-rich organic fertilizer.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Before stocking a nursery or rearing pond with carp spawn, it is essential to eliminate all existing predatory and weed fishes.
Predatory fishes (such as snakeheads and catfishes) will prey on the stocked spawn, while weed fishes (such as minnows) compete with them for food and dissolved oxygen.
Organic piscicides are used to clear these unwanted fish from the pond before stocking.

Step 2: Detailed Explanation:
Mahua oil cake (MOC), obtained from the seeds of the Madhuca indica tree, is a widely used organic piscicide in Indian aquaculture.
It contains about 4-6% of a toxic plant glucoside called saponin.
When applied to pond water at a rate of 250 ppm (or 2500 kg/ha-m), the saponin dissolves and acts as a respiratory poison.
It enters the bloodstream of fish through their gills, where it hemolyzes red blood cells, causing the fish to float to the surface and die within a few hours.
The fish killed with MOC are safe for human consumption.
Additionally, the toxic saponin breaks down completely within 10 to 15 days, after which the decomposed Mahua cake serves as an excellent organic fertilizer, promoting the growth of natural phytoplankton and zooplankton.
While kerosene and diesel are sometimes used to create a surface film to control aquatic insects, they are not used to eradicate predatory fish.
Cottonseed cake is used strictly as a feed ingredient and has no piscicidal properties.

Step 3: Final Answer:
Mahua oil cake is used to eliminate predatory and weed fishes from culture ponds.
Thus, the correct choice is (A).