Reducing Existing Stressors: Invasive Species Management

Quagga Mussels

Maintaining and restoring ecosystem function is a cornerstone of natural resource climate change adaptation. CDFW is pursuing actions that will increase resistance to climate change, promote resilience, enable ecosystem responses, and realign restoration and management activities to better reflect changing conditions. Reducing non-climate stressors, such as habitat destruction and fragmentation, pollution, and invasive species will help improve the ability of natural systems to withstand or adapt to impacts associated with climate change.

Invasive species can be incredibly destructive to biodiversity, ecosystem function, agriculture, and human health . The California Climate Adaptation Strategy specifically calls for restoration and other land stewardship practices that reduce existing stressors and CDFW’s efforts to eliminate or control invasive species is one tangible action that has many benefits to safeguard fish, wildlife, and habitats from continued climate change. Specifically, removing or preventing the establishment of invasive species will support the integrity and function of an ecosystem and help that systems buffer future impacts associated with climate change. To that end, CDFW is focusing resources on restoration, education and outreach, and other land stewardship practices that reduce or prevent environmental stressors in order to improve watershed conditions, enhance ecosystem function, and restore ecosystem services on priority lands.

Quagga/Zebra Mussel Outreach and Action

One of our most notable projects in CDFW related to invasive species pertains to quagga and zebra mussels. In 2007, quagga mussels spread from the Colorado River to lakes in southern California via the Colorado River Aqueduct. Zebra mussels were discovered in an isolated reservoir in central California in 2008. CDFW has designed a program that addresses the concern that ongoing climate change could exacerbate the impacts of these invasive mussels to the state’s fish and wildlife resources, as well as to the water conveyance systems that supply California’s agricultural and urban customers.

CDFW has established several mechanisms for improving program efficiency and effectiveness through collaboration. CDFW’s interagency task force brings together federal and state agencies quarterly to discuss on-going issues and progress towards mussel prevention, control and eradication. This aggressive outreach campaign is designed to help local water agencies and other stakeholders prevent further infestations of invasive mussels. Currently these mussels are restricted to man-made reservoirs but the goal is to keep the mussels out of natural waterways and sensitive habitats where the greatest impacts to native fish and wildlife resources would occur. In an effort to address the various pathways of introduction and spread, CDFW is working with partners to initiate research to determine the risk of invasive mussel spread by sportfishing. This research will help determine which lakes in California have suitable habitat, and whether manipulation of water chemistry is a good control strategy for controlling invasive mussels in water conveyance systems.

Lake Davis Invasive Pike Eradication


The northern pike is a highly invasive species that was threatening Lake Davis reservoir – a renowned trout fishing destination and drinking water supply in Plumas County, California, and the surrounding 44 square miles of tributary streams. This invasive pike was first discovered in Lake Davis in 1994. After years of study and attempts to control and contain the pike in the reservoir, the pike population continued to grow, and the trout fishery continued to decline, as did the related sectors of the local economy. In addition, the threat of the pike escaping the reservoir by spilling over the dam or being moved by humans and devastating other aquatic natural resources of California and the region – including the salmonids and endangered species in the Sacramento-San Joaquin Bay Delta – continued to grow. It was anticipated that if pike had become established in the delta complex of streams, economic impacts of over $ 500,000,000 per year could have resulted in addition to the devastating impacts on ecological values, including a number of threatened or endangered species. Additional impacts on water exports could also have had negative impacts to the farming industries of the central valley and their residents.

In response, CDFW developed the Lake Davis Pike Eradication Project which involved the chemical treatment of Lake Davis to rid the lake and the state of the highly invasive species. The project was a huge success and has not only allowed for the reestablishment of the prized Lake Davis trout fishery, but it has eliminated a major threat to other aquatic natural resources in California. By removing this invasive species CDFW has helped to enhance and restore habitat that will better support the maintenance of robust populations of healthy fish and wildlife in the future. In doing this, CDFW has increased the health and function of the lake offering this ecosystem and a multitude of species a better chance to respond and adapt to future stressors and changes associated with climate change.