Help with pronouns and adjectives? The words in () are pronouns or nouns?

Question

anonymous · Answer

Brown trout, (which) were imported into (this) country in the nineteenth century, are unlike the brook trout (that) we find in the ice-cold streams of Maine. The rainbow trout, (another) native American species, is found in the far west. (Many) steams are now so impure (that) the native trout cannot live in (them) Consequently, (many) have been stocked with brown trout, (which) do not seem to mind warm water. (Both) kinds of trout are splendid game fish, and (both) will readily take a dry fly if (it) looks to (them) like a natural insect. (Many) experts tie flies so small that two dozen of them may easily be put into a thimble. (Many) tie (these) tiny flies to the ends of nylon leaders (which) are fifteen feet long. (Some) fisherman prefer even longer leaders.