Which of the following fishes is famously known in basic zoology for building a nest to protect its eggs?

Introduction:
Reproductive behaviour in fishes can be very diverse. Some species scatter eggs freely, while others show complex parental care such as nest building and guarding. This question checks your knowledge of a classic example of nest building behaviour in fishes mentioned in many zoology textbooks and general knowledge books.

Given Data / Assumptions:
- Options include salmon, catfish, rohu and stickleback. - The focus is on the act of building a nest, not just digging a pit or selecting a site. - The question reflects simplified school level zoology where one fish is highlighted as a famous nest builder. - We assume typical reproductive behaviour in natural conditions.

Concept / Approach:
The stickleback is well known in behavioural studies and zoology as a small fish whose male constructs a nest using plant material and secreted threads. The male then courts females, leads them to the nest to lay eggs, and later guards the nest. This specific nest building is often highlighted in textbooks, which is why stickleback is picked out as the example of a fish that makes a nest.

Step-by-Step Solution:
Step 1: Think of fishes commonly used as classic examples in behaviour and evolution chapters. Step 2: Recall that the male stickleback builds a small tunnel like nest using bits of plants and special glue like secretions. Step 3: Recognise that salmon, catfish and rohu may dig redds or depressions or choose spawning grounds, but the school level nest building example is stickleback. Step 4: Choose stickleback as the fish best matching the description in the question.

Verification / Alternative check:
Behavioural ecology case studies and many general zoology texts describe the nest building, courtship displays and parental care of the three spined stickleback. This cross check confirms that stickleback is the intended textbook answer in basic general knowledge questions.

Why Other Options Are Wrong:
Salmon: They migrate and dig redds in gravel beds to lay eggs but do not weave a nest in the classic sense taught in simple GK. Catfish: Some species show parental care, but they are not the standard nest building example in common exam material. Rohu: A common carp like fish in South Asia, mostly known as a food fish; its breeding habits are not usually described as nest building in basic textbooks.

Common Pitfalls:
Students sometimes assume that any fish that digs or chooses a spawning site is a nest builder and may therefore pick salmon or catfish. However, competitive exams usually expect the specific textbook species that is repeatedly cited for building a constructed nest structure, which is the stickleback. Remembering named case studies can greatly improve accuracy in such questions.

Final Answer:
The fish famously known for building a nest to protect its eggs is the Stickleback.