Spinner Shafter--even her name is a reflection of her father's determination to raise a fisherman (though she herself would rather be a dancer)--astounds her relatives and wins the family trophy from Uncle Auggie by hooking a huge cutthroat trout, a variety thought to' have vanished from the area. But Spinner is shocked and saddened when her father insists on mounting the record-breaking catch instead of throwing it back according to Shafter custom; that's one reason why she is happy when Cousin Al whose cabin she is visiting invites his "city mouse" age mate on a mountain trek with tents and backpacks, to solve the mystery of the lone cutthroat's appearance and the decline of his kind. They do, and besides saving the species they save each others' lives. Spinner earns Al's recognition as a "good woodsperson" -- whereupon she gives up dancing to stay and help in a reforestation project for which their discoveries have won state aid. Though the direction of the switch is updated, both Spinner's early interest in dancing and her later total conversion to her father's model (she even cuts off her long hair) seems just as arbitrary as in the tomboy-to-prom queen changes of the past. And though no one can fault this author's ecology and woodspersonship, the fast-paced mystery plotting she gave a similar theme in Who Really Killed Cock Robin (KR, 1971) is absent from this more thinly populated and leisurely fish story.