FRESHWATER ECOREGIONS OF NORTH AMERICA
a Conservation Assesment World Wildlife Fund (Abell et al., 2000)
In contrast with the BSP freshwater priority setting exercise which was carried out within the Neotropical Realm of which southern Mexico is part of, this exercise is developed within the framework of the Neartic Realm which constitutes a more appropiate biogeographical comparasion field for northern Mexico. In contrast to the BSP exercise, this one is based on best available quantitative data sets for: fish, crayfish and herpentofauna, and mussels for Northern Mexico.
Upper Río Grande  (not in Mexico)
Pecos  (not in Mexico)
Cuatro Ciénegas 
11 Rio Conchos 
12 Lower Río Grande  13 Río San Juan 
14 Río Salado 
High levels of fish endemism and spring Endangered fauna. Continentally Outstanding
Continentally Outstanding Globally Outstanding
Outstanding fish endemism, including minnows, darters,mosquitofish and platyfish.
Gila  (Mex. Upper San Pedro)
Continentally Outstanding Three endemic or near-endemic fish genera (Meda, Plagopterus, Tiaroga) US, Mex? Continentally Outstanding Endemic Fishes specially addapted to the high- flow large-river system (Xyrauchen, Lepidomeda, Plagopterus) US, Mex?
Colorado  (Mex. Colorado Delta)
Major Freshwater Ecoregion Habitat Type PACIFIC BIOREGION - Coastal Complex
ARTIC - ATLANTIC BIOREGION - Río Grande Complex
PACIFIC BIOREGION - Colorado River Complex
South Pacific Coastal 
Continentally Outstanding One endemic fish and invertebrate endemism in thermal springs (Fontellicella, Tryonia, Thermosphaeroma) Continentally Outstanding High fish richness and endemism for the Rio Grande Complex, including three pupfish (Cyprinodon), Etheostoma, Cichlasoma, Cyprinella and Gambusia, Continentally Outstanding Endorheic habitats; high levels of endemism among fish; spring and subterranean habitats, Continentally Outstanding Extinct monotypic fish genus (Stypodon) and exant endemic fish genus (Megupsilon) Globally Outstanding Diverse complex of hundreds of geothermal springs, lakes and streams; high beta- diversity Globally Outstanding Only free-flowing river habitat left in Rio Grande catchment; high levels of endemism in cave and spring habitats.
Continentally Outstanding Southernmost populations of anadromous
Pacific lamprey and steelhead; near-endemic fish genus (Encyclogobius), found in coastal lagoons.
XRLS = Xeric-Regions Rivers, Lakes and Springs. ERLS = Endorheic Rivers, Lakes and Springs. TCRL = Temperate Coastal Rivers, Lakes and Springs
LTR = Large Temperate Rivers SCRL = Subtropical Coastal Rivers, Lakes and Springs