NCERT Class 9 Science — Chapter 3: Improvement in food resources

mcqeasy

In a composite fish culture system, which one of the following species functions as a bottom feeder?

Official previous-year question

Verified 1 Aug 2026.

Options

ACatla
BRohu
CSilver Carp
DMrigal

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Solution

Correct Option

The correct option is

Mrigal

Explanation

Composite Fish Culture (Polyculture) is a method of aquaculture where multiple fish species with compatible but distinct feeding habits are reared together in a single pond. This ensures that food resources in all ecological zones of the water body are utilized efficiently without inter-species competition.

The species are selected based on their feeding zones:

Surface Feeders: These species feed on zooplankton and phytoplankton found in the upper layer of the water. Examples include Catla (Catla) and Silver Carp.
Column Feeders: These species inhabit the middle zone of the pond. An example is Rohu (Labeo rohita).
Bottom Feeders: These species forage at the bottom of the pond, consuming decaying organic matter and detritus. Examples include Mrigal (Cirrhinus mrigala) and Common Carp.
Weed Feeders: Species such as Grass Carp feed on aquatic macrophytes and weeds.

Therefore, Mrigal is the species that functions as a bottom feeder in this system.

Key Takeaway: In a standard composite fish culture system, Catla occupies the surface zone, Rohu occupies the column zone, and Mrigal occupies the bottom zone.

Your note

More from Chapter 3: Improvement in food resources

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In the context of sustainable agriculture, what does the term 'Green Manure' refer to?

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Consider the following statements regarding weeds: 1. Xanthium and Parthenium are examples of beneficial crops. 2. Weeds compete with crop plants for food, space, and light. 3. Weeds are beneficial as they enhance nutrient absorption by crop plants. Which of the statements given above is/are correct?

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In the context of insect pests attacking plants, which of the following modes of attack are observed? 1. Cutting the root, stem, and leaf. 2. They provide nutrients to the plant by sucking cell sap. 3. Boring into stems and fruits. Select the correct answer using the code given below:

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Which one of the following agricultural practices is primarily used as a preventive measure for weed control?

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Correct Option

The correct option is

Mrigal

Explanation

The species are selected based on their feeding zones:

Surface Feeders: These species feed on zooplankton and phytoplankton found in the upper layer of the water. Examples include Catla (Catla) and Silver Carp.
Column Feeders: These species inhabit the middle zone of the pond. An example is Rohu (Labeo rohita).
Bottom Feeders: These species forage at the bottom of the pond, consuming decaying organic matter and detritus. Examples include Mrigal (Cirrhinus mrigala) and Common Carp.
Weed Feeders: Species such as Grass Carp feed on aquatic macrophytes and weeds.

Therefore, Mrigal is the species that functions as a bottom feeder in this system.

Key Takeaway: In a standard composite fish culture system, Catla occupies the surface zone, Rohu occupies the column zone, and Mrigal occupies the bottom zone.