shell collecting vs assembling

shell collecting and assembling both are nouns.

Word	Noun	Adjective	Verb	Adverb
shell collecting	Yes	No	No	No
assembling	Yes	No	No	No

As nouns, assembling is a hypernym of shell collecting; that is, assembling is a word with a broader meaning than shell collecting:

Other hypernyms of shell collecting include aggregation, collecting, collection, malacology.

shell collecting (noun)	assembling (noun)
the collection and study of mollusc shells	the act of gathering something together