The primary reasons for the endangered status of the Rio Grande sucker are:
Habitat loss and degradation: This is the most significant threat to the Rio Grande sucker. Their natural habitat consists of shallow, clear, warm streams with gravel and cobble bottoms, and plenty of aquatic vegetation. Alteration and destruction of these habitats due to human activities such as water diversions, dam construction, channelization, and urbanization have led to a significant reduction in the sucker's range and population.
Pollution: The introduction of pollutants, including agricultural runoff, sewage, industrial contaminants, and chemicals into the Rio Grande has further degraded the water quality and adversely impacted the sucker's habitat. Polluted water can affect the sucker's health, reproduction, and feeding behavior.
Overfishing: In the past, the Rio Grande sucker was caught as a food source and used as bait by anglers. Unsustainable fishing practices contributed to the decline of the species, especially during periods when their population was already vulnerable due to habitat loss and degradation.
Predation: Introduced non-native species, such as the red shiner and the largemouth bass, have become established in the Rio Grande and prey upon the Rio Grande sucker, adding further pressure on its already diminished populations.
Competition: Competition for food and habitat from other native and non-native fish species also pose challenges for the survival of the Rio Grande sucker.
Conservation efforts, such as habitat restoration projects, water management plans, and regulations on water withdrawals and pollution, have been implemented to mitigate these threats and protect the remaining populations of the Rio Grande sucker. However, these efforts are crucial for the long-term survival and recovery of this endangered species to address these ongoing threats effectively.