Seeding Sierra Streams With Trout May Have Depleted Frog Population

Trout planted in Yosemite National Park’s lakes and streams over the decades may partly explain declines in frog and toad populations, scientists say. Results of a 1992 survey published in the current issue of Conservation Biology indicate that there were fewer frogs and toads of most types than in 1915.

Researchers said people began stocking Sierra streams in the 1920s with trout, which eat frog eggs, tadpoles and adult frogs. Other factors such as pollution and increases in ultraviolet light also may have played a role, said Charles Drost, a former National Park Service zoologist.