In 1997, a group of approximately 40 ichthyologists, biologists and naturalists from several U.S. and Mexican institutions formed a collaborative group, Truchas Mexicanas, to study the diversity of Mexican native trout. Between 1997 and 2005, members of the group explored the rivers and streams of the Sierra Madre Occidental collecting specimens for study and documenting the diverse populations of Mexican native trout. In 2002, fisheries biologist Robert J. Behnke published Trout and Salmon of North America documenting a lifetime study of North American trout and salmon. In Trout and Salmon of North America, Behnke described two species of trout—the Mexican golden trout (O. chrysogaster) and the Mexican rainbow trout (O. m. nelsoni and O. m. ssp). He described a number of local forms of the Mexican rainbow trout primarily based on the river systems they occurred in.