Current work in wildlife, rivers, public lands, and climate

The Service issued initial findings in 2016 that both species may warrant protections under the ESA, but several years passed with no proposed listings in sight. In 2020, Guardians challenged the Service’s failure to extend ESA protections to these species as part of a complaint that included five freshwater species and their imperiled habitats in the Rio Grande and Missouri River. 

“New Mexico’s rivers were named the most endangered in the country this year, and both the Rio Grande chub and sucker depend on the Rio Grande and its tributaries,” said Joanna Zhang, wild rivers advocate with WildEarth Guardians. “It’s disappointing to see the Service deny protections to two species whose populations have been in severe decline, especially when climate change will only exacerbate current threats.” 

The Rio Grande chub (chub) and Rio Grande sucker (sucker), both native to the Rio Grande Basin, have experienced significant declines in population due to habitat destruction, climate change, invasive species, and the impacts of human land and water uses. Once abundant throughout the Rio Grande Basin, the chub has disappeared from 75% of its historic range and the sucker is now considered rare in Colorado and has mostly disappeared from the Rio Grande in New Mexico.

Known for its distinctive red-orange coloring during spawning season, the Rio Grande chub is a small fish that is mostly found at higher elevation pools where water temperatures are cooler, and prefers a braided, sandy, and wide river channel with ample bank vegetation to provide shade. Meanwhile, the shiner – a slender, silver-colored fish – lives in low-velocity streams featuring aquatic vegetation and a gravel- or rubble-covered streambed where algae can grow.

Dams, diversions, groundwater pumping, and other human impacts have dewatered and changed the free-flowing nature of the Rio Grande. The decline of the Rio Grande chub and sucker highlights the broader challenges faced by many species in the region. 

Zhang added, “The loss of native species in the Rio Grande is an indication that the entire river system is in crisis, and the Service needs to protect vulnerable species and help shape the systemic changes to water management we need to restore healthy and living rivers.” 

Rio Grande Chub

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