In his youth, writes Hawaii-based photographer and marine biologist Doug Perrine, "the word "shark" was synonymous with "man-eater," and the very mention of sharks was taboo in the recreational diving industry." In the last two decades, however, the public perception of sharks has changed, so that sharks are seen less as mindless and lethal eating machines than as necessary predators who play an important role in the ocean"s ecology. Perrine reinforces the new view of sharks with this sympathetic study, which traces the evolution of sharks and their cousins, the rays, over millions of years, and which touches on important aspects of shark behavior. Perrine follows his general discussion with "snapshots" of selected individual species (worldwide there are 465 species of shark and 627 species of ray), offering notes on favorite habitats and foods, mating habits, and other features. Perrine accompanies his text with large-format plates. Sadly, he remarks, even as we are coming to understand the sharks and rays better, their numbers are growing fewer as commercial fisheries serve new markets for shark fins, cartilage, and meat. "Populations must be managed if they are to continue to exist," he notes, adding that conservation groups have risen in just the past few years to speak on the sharks" behalf, "something I could have barely imagined just a decade ago." --Gregory McNamee