Question

In case of excessive phytoplankton which species is preferred to stock

• A. Silver carp
• B. Grass carp
• C. Common carp
• D. None

Hint:

Silver carp is widely used in municipal reservoirs and aquaculture ponds globally to prevent cyanobacterial (blue-green algae) blooms.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
An overabundance of phytoplankton can cause severe algal blooms, leading to dissolved oxygen depletion at night and potential fish kills.
Biological control using filter-feeding herbivorous fishes is an effective and eco-friendly way to manage excessive phytoplankton.

Step 2: Detailed Explanation:
Let us look at the feeding habits of the options:
1. Grass carp (Ctenopharyngodon idella): Feeds on macro-vegetation and aquatic weeds.
2. Common carp (Cyprinus carpio): An omnivorous bottom-feeder.
3. Silver carp (Hypophthalmichthys molitrix): A specialized filter-feeding phytoplanktivorous fish.
Silver carps have highly adapted gill rakers fused into a sponge-like network, allowing them to filter microalgae from the water.
Stocking Silver carp in a pond with excessive phytoplankton ensures rapid filtration and biological control of the algal bloom.

Step 3: Final Answer:
In case of excessive phytoplankton, Silver carp is preferred to stock.