Center for Biological Diversity

Advocating for Fish Stocking Reform to Protect
California’s Imperiled Fish and Amphibians



California Red-legged Frog


River and Watershed Protection

Biological Diversity and Endangered Species

Western Native Trout Campaign

Mountain Yellow-legged Frog

In California and many other places throughout the West, native trout and amphibian populations are getting smaller and smaller. Scientists have shown a direct link between non-native fish stocking and these declines, which are devastating such species as the Golden Trout, Lahontan Cutthroat Trout, Mountain Yellow-legged Frog, Yosemite Toad and Cascades Frog.

Despite the numerous studies that prove fish stocking is causing serious declines in native fish and amphibians, the California Department of Fish and Game (DFG) has refused to conduct an environmental review of its stocking practices. The Center’s fish stocking reform effort is working to hold the state of California accountable for its actions and ensure that native species receive the protection they need and deserve.

Why Fish Stocking Is a Problem

Fish stocking creates three main problems for California’s natural environment:

1) Each and every time a lake or stream is stocked with non-native fish there is a risk of spreading disease, exotic organisms and unwanted fish;

2) Non-native, stocked fish prey on and compete with native species for food and habitat, and;

3) Stocked fish are altering the natural ecosystem to the detriment of the native species.

For example, most native trout in California are listed as threatened or endangered under the Endangered Species Act, and fish stocking threatens nearly all of them. Indeed, scientists believe that non-native trout stocking is the single biggest factor in the decline of native fish species in the Sierra Nevada. A number of amphibians are also listed as threatened or endangered or are candidates for listing in part because of fish stocking, including the Arroyo Toad, Mountain Yellow-legged Frog, Yosemite Toad, California Red-legged Frog and others.


Introduced trout eating another fish
Photo by USFWS

To evaluate the potential effects of fish stocking on native species in California, the Center obtained a record of all water bodies stocked with trout in 2005 and compared this with the locations of imperiled native fish and amphibians contained in the California Natural Diversity Database. Based on this analysis, the Center identified a minimum of 47 waters where trout were stocked and imperiled species were present, affecting at least 39 different kinds of imperiled fish and amphibians. Given that this only reflects stocking in 2005 and likely underestimates the number of waters where harmful stocking occurred, this is likely the tip of the iceberg in terms of the impacts of non-native trout on California’s natural heritage. Many more species continue to be impacted by fish that were stocked over the past 150 years.

Addressing the impacts of non-native trout stocking

Our goals are two-fold. We aim to: 1) protect existing quality habitat and healthy native fish and amphibian populations from further degradation and 2) secure protection of high-quality watersheds from the threat of future stocking.

The Center and our colleagues submitted comments in August 2005 and again in July 2006 requesting that DFG initiate an environmental review on its fish stocking practices to alleviate the impacts on imperiled aquatic species. After no review was conducted, we brought our case to court on October 5, 2006. In our legal suit we are asking the court to force DFG to investigate and reverse the environmental impacts of its fish-stocking program.

Learn More:

The Need for Fish Stocking Reform in California
FAQ's
Table of CA Species Impacted by Stocking in 2005
Effects of Stocking-up Freshwater Food Webs (study)
Fish stocking limits species in Klamath Mountains (study)
Additional Links

Other Materials:

Read our press release
Read our comments to the California Dept. of Fish and Game