Question

Values of alkalinity (mg/l) that adversely affect the spawning and hatching of carps are

• A. Less than 100
• B. More than 300
• C. 100 - 150
• D. 150-200

Hint:

Water Quality for Hatcheries:
- Ideal pH: 7.5 - 8.5
- Ideal Alkalinity: 80 - 150 mg/l
- Hardness: Moderate (75 - 150 mg/l)
High alkalinity ($>$ 300 mg/l) creates a stressful environment for embryonic development.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks about the upper threshold of total alkalinity in water that interferes with the reproductive success (spawning and hatching) of Indian Major Carps.
Detailed Explanation:

• Alkalinity and Spawning: Total alkalinity refers to the buffering capacity of water, primarily provided by carbonates, bicarbonates, and hydroxides. For carp culture and breeding, a moderate range of alkalinity is essential.

• Optimum Range: The ideal range of total alkalinity for successful spawning and egg hatching in carps is generally between 75 mg/l and 150 mg/l (some literature suggests up to 200 mg/l).

• Adverse Effects of High Alkalinity: When alkalinity exceeds 300 mg/l, it often correlates with high pH and high hardness levels. Such conditions can lead to poor fertilization rates and can be lethal to the delicate developing embryos. High alkalinity can interfere with the swelling of the perivitelline space in the eggs and the subsequent enzymatic processes during hatching.

• Low Alkalinity: While values below 20 mg/l can lead to unstable pH and poor productivity, values slightly less than 100 mg/l (like 70-80 mg/l) are still within a functional range for spawning.

Step 3: Final Answer:
Values more than 300 mg/l are considered detrimental to the spawning and hatching processes in carps.