• Wizard Island

    Crater Lake

    National Park Oregon

How are crayfish affecting Mazama Newts?

The Mazama Newt likely inhabited the entire lake shoreline since they colonized the lake as early as 6,000 years ago.

  • The figure below shows that the Mazama Newt only occupies 50% of the habitat with crayfish inhabiting the other 50%.
  • There are very few sites with both crayfish and newts.
  • Crayfish were introduced to the lake by humans in 1914 for fish food.
  • Studies with newts and crayfish in tanks show that crayfish will kill newts and/or force then to flee to other areas.

 
Locations of newts and crayfish in Crater Lake.
Locations of Mazama Newts and crayfish in Crater Lake.
NPS
 
food availability with and without crayfish
Experiments show that where crayfish are located in Crater Lake the number of aquatic insects is reduced.  The left (blue) bar shows the number of insects with no crayfish.  The right (red) bar shows insect numbers with crayfish present.  Both crayfish and newts depend upon insects for food.
NPS

Did You Know?