There are nearly 1,000 species of freshwater fishes in North America alone, and identifying them can sometimes be a daunting task. In fact, in just the twenty years since publication of the first edition of the Peterson Field Guide to Freshwater Fishes, the number of species has risen by almost 150, including 19 marine invaders and 16 newly established nonnative species. This second edition incorporates all of these new species, plus all-new maps and a collection of new and revised plates. Some of the species can be told apart only by minute differences in coloration or shape, and these beautifully illustrated plates reveal exactly how to distinguish each species. The guide includes detailed maps and information showing where to locate each species of fish--whether that species can be found in miles-long stretches of river or small pools that cover only dozens of square feet. The ichthyologic world of the twenty-first century is not the same as it was in the twentieth, and this brand-new edition of the definitive field guide to freshwater fishes reflects these many changes.