Mountains Restoration Trust Still Battling Invasive Crayfish in Santa Monica Mountains


(OAK PARK, CALIFORNIA) The water flowing through Medea Creek is overrun with invasive crayfish.

The red swamp crayfish is an invasive species in Southern California, and they continue to destroy the ecosystem in many of the creeks and streams found in the region. They consume almost all life in these important waterways like fish, amphibians, even plants.


Their consumption of dragonfly nymphs, which are the aquatic form of dragonflies before they mature, is specifically alarming. These small insects are one of the main predators of mosquito larvae. These dragonfly nymphs help control the mosquito population, along with other animals like frogs. This, in turn, aids in prevention of diseases spreading around the local housing communities nearby.


(OAK PARK, CALIFORNIA) A volunteer holds up one of the crayfish removed from Medea Creek.

Studies have shown that when crayfish are present in streams dragonfly nymph numbers are lower than when there are no crayfish. Results of these studies ultimately reveal how this relationship directly affects the mosquito population. The likeliness of mosquito-borne diseases spreading is increased when the crayfish consume valuable species like dragonfly nymphs and frogs.


Data from the scientific journal Conservation Biology (Graphic by Rick Evans)

The Mountains Restoration Trust (MRT) organization, has been dedicated to addressing this issue</