Complex sentence: Populations have been recognized from the mainstream Gila River (above confluence with Mangus Creek) in New Mexico, this includes West, Middle and East forks of the Gila River, along with the San Carlos River (a tributary to the Gila).
Split into simpler sentences: Populations have been recognized from the mainstream Gila River (above confluence with Mangus Creek) in New Mexico. This includes West, Middle and East forks of the Gila River, along with the San Carlos River (a tributary to the Gila).