In "The Fish" by Elizabeth Bishop, where does the poem turn and shift its attention to something different?

In this excellent poem,
the speaker describes the experience of catching a fish which hadn't really fought to escape.
The poem describes the fish objectively, without emotion, talking about the "tiny white sea
lice" that "infest" it. What moves the poem towards its shift is when the speaker
begins to view the fish objectively. As she stares at it, we are told that the speaker
"admired his sullen face." As she continues to contemplate the fish, she sees
something else that brings on an epiphany in her and leads to her decision to let the fish
go:

and then I saw
that from his lower
lip
--if you could call it a lip
grim, wet, and weaponlike,
hung five
old pieces of fish-line,
or four and a wire leader
with the swivel still
attached,
with all their five big hooks
grown firmly in his mouth.

This evidence of the fish's earlier battles for survival and his
evident success increases the speaker's admiration and respect for the fish. As nature and the
light combine to make everything appear a "rainbow," the speaker lets the fish go as
"victory filled up / The little rented boat." The speaker comes to some unspoken
understanding with the fish and understands his battle for survival and cannot do anything else
but let him go again.