Here's why:
* Noun: A noun is a word that names a person, place, thing, or idea. In this sentence, "fish" is the thing being caught. It's the object of the verb "catching."
Let's break down the sentence:
* Catching: This is the present participle of the verb "to catch," acting as the main verb in the sentence.
* one: This is a pronoun referring to "fish."
* oldest pastimes: This is a noun phrase, functioning as the object of the preposition "of" (which is implied in the sentence).
Therefore, "fish" is the noun that is being "caught" and is part of the noun phrase "one oldest pastimes."