To hear some people tell it, the increasingly energetic and sophisticated fishing industry has left the world’s oceans a shambles, with species of cod, sharks, tuna and other fish hunted almost to extinction and vast stretches of the ocean floor wrecked by bottom-scraping trawlers.

To hear some other people tell it, many depleted stocks are recovering nicely.

Ray Hilborn, a fisheries scientist at the University of Washington, wades into this disagreement in his new book and comes out with a lucid explication of a highly tangled issue.

Each argument, he concludes, has some truth on its side. “It depends on where you look,” he writes. “You can paint horror story after horror story if you want. You can paint success after success.”

He navigates the path between horror and success through scores of questions and answers, nearly all of which demonstrate how difficult it is to sort this issue out.