Two Frogs Added to Threatened Species List

By Dana M. Nichols

February 05, 2012

Record Staff Writer

SAN ANDREAS – The California Fish and Game Commission last week voted unanimously to add two species of mountain yellow-legged frogs to the state’s list of threatened or endangered species.

State officials say the listing will give them more flexibility in stocking popular trout species in remote Sierra Nevada lakes at 5,000 feet or higher. The trout eat tadpoles and are one of several factors in the dramatic decline of the two species, according to state scientists.

A decade ago, state officials halted trout stocking in more than a hundred lakes. Now that the frog species are listed, scientists will develop plans for each local population and those plans, in some cases, will allow the resumption of stocking trout for recreational anglers, Department of Fish and Game Environmental Scientist Mitch Lockhart said.

The Sierra Nevada mountain yellow-legged frog is threatened with extinction. The southern mountain yellow-legged frog has been given the more serious “endangered” listing.

Scientists say both species have declined rapidly in five decades because of the trout stocking, exposure to pesticides, and a fungal infection that eventually destroys every population where it is introduced.

Stafford Lehr, chief of the fisheries branch for the California Department of Fish and Game, said scientists in the last decade visited more than 15,000 sites where the yellow-legged frogs once lived and found them absent from 76 percent of the watersheds they once occupied.

In the watersheds where the frogs do survive, their numbers are greatly reduced. “Ten, twelve, fifteen individuals,” Lehr said of the typical yellow-legged population in an entire watershed.

In contrast, written accounts from the 1920s, the 1930s and even as recently as the 1960s indicate the frogs were then abundant. “When approaching an alpine lake, there were so many frogs you could not avoid walking on them,” Lehr told the commission.

State and federal scientists said they have an exceptionally large amount of data on the two frog species.

Several commissioners who usually oppose the listing of new species said the completeness of that data persuaded them to support the listing.

Commissioner Daniel Richards of Upland asked if state game staff would still seek to allow trout stocking and angling where possible.

However, “It’s not going to be easy” to do the necessary science, Lehr said of that part of the management plan.

At one time, state authorities stocked 617 remote mountain lakes with trout. Already, stocking has been halted at 113 lakes to reduce pressure on yellow-legged frogs.

“As a result, some of these lakes have gone fishless,” Lehr said.

At the same time, the elimination of fish from a number of lakes has helped local yellow-legged frog populations to rebound, he said.

The Center for Biological Diversity has been seeking greater protection for the frogs for years. In 2000, it asked the federal government to list the frogs as endangered under the federal Endangered Species Act. Federal scientists in 2002 placed the two species on an indefinite waiting list.

The Center for Biological Diversity in 2010 asked state authorities to list the frogs. Although the center wanted both species listed as endangered, center senior attorney Lisa Belenky told the commission she was pleased with the decision the commission made.

“The yellow-legged frog is really an indicator of the health of our environment,” she said.

The southern yellow-legged frog is in worse shape and is gone from 87 percent of the watersheds where it once lived, Lehr said. It was once common in lakes in the San Gabriel, San Bernardino and San Jacinto mountains in Southern California as well as a portion of the southern Sierra Nevada.

The Sierra Nevada yellow-legged frog lives in the portions of that mountain range north of Fresno County.

Contact reporter Dana M. Nichols at (209) 607-1361 or dnichols@recordnet.com. Visit his blog here.