Why Endangered

**NOTE: General information, not specific to humpback chub**

Water Development

• Human population growth
  • Created a significant demand for water and hydro electrical power in western stated
  • Hundreds of water projects (dams, canals, irrigation projects) have been constructed in the Colorado River
• Restricted the fish to about 25 percent of their former range
• Blocked some spawning migration routes of the Colorado pikeminnow and other species
• Waters are 15 degrees colder than the rare fishes’ preferred habitat
  • From the tailwaters downstream of the dams

Wetlands

• The number and size of life-supporting wetlands has been cut dramatically across the nation
  • Over the last 200 years, Colorado has lost an estimated 50 percent of its wetlands
• Young native fish have depended on these areas, which enables them to grow significantly faster and provides them warmer, slower-moving water chock-full of microscopic food

Non-Native Fish

• Introductions of non-native fish into rivers, lakes and reservoirs also have taken a toll on the native fish
  • Historically, there were only 14 fish species in the upper Colorado River Basin
  • In the late 1800s, private citizens and state and federal wildlife agencies began stocking non-native fish into lakes, reservoirs and streams in the Colorado River drainage
  • Now endangered fish have to compete with more than 40 non-native species
• Non-native species (such as northern pike, channel catfish, red shiner and fathead minnow) are efficient predators that prey on the eggs and young of endangered fish

Selenium

• Some portions of the upper Colorado River basin have high levels of selenium
• Animals need this naturally occurring element in trace amounts
• But in larger concentrations, selenium can cause severe birth defects in wildlife

Anglers

• Angling is a method of fishing by means of an "angle" (hook).
• Some native fish have been killed by anglers who did not release the fish properly
• Prefer non-natives fish
  • After hooking a native fish, the anger may have tossed it on the riverbank to die

Other Factors

• Pollution
• Parasites
• Hybridization