Goodson, Gar. Fishes of the Pacific Coast. Stanford, CA: Stanford University Press, 1988. Over 500 beautifully detailed color drawings highlight this pocket version of all you ever wanted to know about the ocean’s fishes (including common Spanish names) from Alaska to Peru.
Howell, Steve N. G. Bird-Finding Guide to Mexico. Ithaca, NY: Cornell University Press, 1999. A unique, portable guide for folks who really want to see birds in Mexico. Unlike other bird books, the author presents a unique and authoritative site guide, with dozens of clear maps and lists of birds seen at sites all over Mexico. Pacific sites include Mazatlán, San Blas, Puerto Vallarta, El Tuito, Manzanillo, Oaxaca, and many more. Use this book along with Howell and Webb’s A Guide to the Birds of Mexico and Northern Central America.
Howell, Steve N. G. and Webb, Sophie. A Guide to the Birds of Mexico and Northern Central America. Oxford: Oxford University Press, 1995. All the serious bird-watcher needs to know about Mexico’s rich species treasury. Includes authoritative habitat maps and 70 excellent color plates that detail the males and females of around 1,500 species.
Leopold, Starker. Wildlife of Mexico. Berkeley: University of California Press, 1959. Classic, illustrated layperson’s survey of common Mexican mammals and birds.
Mason, Jr., Charles T., and Patricia B. Mason. Handbook of Mexican Roadside Flora. Tucson: University of Arizona Press, 1987. Authoritative identification guide, with line illustrations, of all the plants you’re likely to see in the Puerto Vallarta region.
Morris, Percy A. A Field Guide to Pacific Coast Shells. Boston: Houghton Mifflin, 1974. The complete beachcomber’s Pacific shell guide.
Pesman, M. Walter. Meet Flora Mexicana. Published in Arizona, in 1962, by D. S. King, now out of print. Find it at www.amazon.com  or a larger library. Delightful anecdotes and illustrations of hundreds of common Mexican plants.
Peterson, Roger Tory, and Edward L. Chalif. Field Guide to Mexican Birds. Boston: Houghton Mifflin, 1999. With hundreds of Peterson’s crisp color drawings, this is a must for serious bird-watchers and vacationers interested in the life that teems in the Puerto Vallarta region’s beaches, jungles, lakes, and lagoons.
Wright, N. Pelham. A Guide to Mexican Mammals and Reptiles. Mexico City: Minutiae Mexicana, 1989. Pocket-edition lore, history, descriptions, and pictures of commonly seen Mexican animals.