In '' The Fish'' why does the speaker let the fish go at the end of the poem?Elizabeth Bishop's "The Fish" --Please defend your answer

"The Fish" is a poem in which the speaker, as a respecter of life, becomes sympathetic to the fish.  In line 34 the speaker says she

looked into his eyes/which were far larger than mine/but shallower...the irises backed and packed/...seen thruogh the lenses of old scratched isinglasss

It is at this point that the speaker perceives the old fish as a venerable character from whose lip hang

five old pices of fish-line...Like medals with their ribbons/frayed and wavering,/a five-haired beard of wisdom/trailing from his aching jaw.

That this old fish has beaten five other fisherman causes the speaker to revere the fish.  She thinks, she "stares" and "victory filled up the little rented boat."  Who is she to reel in this venerable fish, who has survived for so long against five other adversaries?  Out of respect and sympathy for the fish who has won these previous battles, she throws him back.

In her calm, understated tone, Elizabeth Bishop moves from the ordinary description of a fish similar to a ling or cod to a philosophical insight.  As the speaker states and "victory" fills the boat, she remarks that "everything was rainbow, rainbow, rainbow!" before she lets the fish go.  It is at this point that the speaker realizes the wisdom of revering life, especially the life of one who has struggled to live and endure.