What does the boy give up for Sheila in "The Bass, the River, and Sheila Mant"? What does he learn from the experience?

The boy gives up the chance to catch "the biggest bass (he) had ever hooked" for Sheila Mant. The bass is so huge that it is able "to draw a fully loaded canoe backward - the thought of it (makes the boy) feel faint." Sadly, Sheila has just expressed an antipathy towards fishing, and the boy is intent on impressing her and keeping her happy. The boy almost has the bass, all he needs to do is to grab the rod and reel it in, but in his determination not to do anything that might ruin his chances with the girl of his dreams, he lets the fish go.

The boy's date with Sheila ends in disaster. After paying little, if any, attention to him during the dance, she comes over when the music has stopped and announces that she is going home with another boy, Eric Caswell. This conclusion had been evident to all but the narrator, as Sheila had shown no interest in him throughout the narrative, and had even mentioned Eric twice on their ride to the dance. When Sheila announces her intention to go home "in Eric Caswell's Corvette," she looks at the boy for the first time that night and tells him he's "a funny kid."

After the dance, the boy reflects on what has happened, and says, "it was these secret, hidden tuggings in the night that claimed me." The tuggings of which he speaks are the physical and romantic longings set off by a beautiful woman, which caused him in this instance to sacrifice the chance to catch the biggest fish he had ever come across. From his experience, the boy has learned that the allure of a woman is fleeting, but that being true to himself and his own nature is a call which must be recognized. The boy is a fisherman through and through, and he regrets his decision to sacrifice the bass for the attentions of a woman who does not even, in the end, care about him. The boy gives a name to the "tuggings" on his heart, and resolves never to make "the same mistake again."