Monitoring Exotic Species


The Eel River was historically dominated by cold water fishes, except for some larger mainstem reaches where the native warmwater fish such as the Sacramento sucker would thrive. The 1964 flood caused profound changes in the main river channels as pools filled and the Eel River became wide and warm in summer.

In 1978, the Sacramento pikeminnow, formerly known as the squawfish, was introduced into Lake Pillsbury within the Potter Valley Project. Within a decade, they had spread throughout the Eel River basin. Studies in the 1990’s indicated that the basinwide population was in the millions and people were concerned about predation by this non-native fish on salmon and steelhead juveniles.

In less than 40 years this highly adaptive species has spread throughout the Eel River basin and colonized every available ecological niche.  Basin residents would like to see the pikeminnow population studied and controlled.  ERRP has a plan to begin such work, with grant assistance from the Salmon Restoration Association.  See the Eel River Sacramento Pikeminnow Monitoring and Management Plan.

Our work on pikeminnow in the Eel River basin is assisted by the guidance of Dr. Bret Harvey, of the U.S. Forest Service Redwood Sciences Laboratory, who is an authority on warmwater fish and has extensively studied the Eel River. He is helping design our monitoring strategy, will train volunteers in fish identification, and assist with analysis.
Read our 2016 Pikeminnow report.

Other Warm Water Species

We have found warm water adapted, non-native fish and aquatic species throughout the Eel River basin. Populations of these fish increase substantially during drought.

Green sunfish, largemouth bass, and brown bullhead are common escapees from farm ponds and there is evidence of spawning and reproduction in recent summers. Bull frogs proliferate in ponds and decimate native frog species as they spread downstream

Thousands of Suckers near Dyerville
Territorial green sunfish in South Fork Eel 

University of California Berkeley researchers have also found the red slide turtle and red swamp crayfish. The snail, radix auricularia, native to Europe and Asia, has now colonized the South Fork Eel River and the lower main river to the estuary.

Introduction of non-native species is not legal and is highly undesirable.  Ponds should be drained annually to prevent establishment of non-native species.