Why does the speaker let the fish go?

In
's famous poem "," the speaker spends most of the poem describing what she sees as she
looks at the fish, and the poem ends, of course, with the speaker letting the fish
go. 

Early in the poem, the speaker notes that the fish "didn't fight. /
He hadn't fought at all" (5-6). This seems a bit unusual, but then the speaker goes on to
record other details and observations about the fish's appearance. The fish is described as
"venerable," with "skin . . . / like ancient wallpaper" (8, 10-11). The word
venerable, paired with "homely" is an interesting choice on Bishop's part. To venerate
something is to respect it, usually due to its age or wisdom. Homely is a less positive word,
making the fish seem ordinary and not beautiful. However, it could also mean that the fish is at
home or comfortable in that place.

The fish is "speckled" and
"infested," which seems to further indicate that the fish is quite ugly and nothing to
really be admired; however, his age is...