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.