Mosquito Fish, Ozone Drop, Fires Are Bad News for Newts

The California newt is in hot water.

Recent studies show ozone depletion and tree-devouring wildfires have torn away the blanket of shade that once protected streams in the Santa Monica Mountains, exposing the newt’s fragile eggs to harmful ultraviolet rays. The result is laying waste to what was once a thriving local population of the salamanders.

If that were not enough, even the government seems to have it in for the newt.

Greater Los Angeles County Vector Control has for years been giving tiny mosquito fish to residents as an effective tool against water-borne mosquito larvae. Trouble is, the only thing mosquito fish like more than mosquito larvae is newt larvae, said Lee Kats, a herpetologist at Pepperdine University, who has made a study of the dwindling salamander.

David Wake, director of the Museum of Vertebrate Zoology at UC Berkeley, said that although the California newt is not classified as an endangered species, it could easily wind up becoming another casualty in the global decline of amphibians, first noted in the 1980s.

The California newt, which is tannish brown on top and yellow to orange on bottom, lives in the California coastal mountains from Mendocino County to Baja, and in the central Sierra Nevada.

Jack Hazelrigg, district manager of the county’s Vector Control, acknowledged that mosquito fish are now in “every habitat you can possibly imagine.”

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But he said the benefits of mosquito fish--a reduction in the number of bloodthirsty and disease-carrying mosquitoes--outweigh their “negligible” impact on the environment.

The county’s Vector Control first brought mosquito fish from the East Coast in 1952, and every year, abatement officials say, they distribute more than 10,000. Hazelrigg said Vector Control intends them to be used in natural and artificial ponds, and does not condone putting the fish in open streams.

But he acknowledged that there are no controls over how the mosquito fish are used.

These days, nary a newt can be found in many Southern California streams, although there are plenty of mosquito fish, say biologists.

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Stooping in a pool of still water in the Santa Monica Mountains near Calabasas, Kats peers intently through the muck, looking for signs of amphibious life. He finds instead a swarm of mosquito fish--so many that the water bubbles with them. With one dip of his fish net Kats catches a few of the writhing, glistening guppies.

“This habitat is perfect for amphibians,” Kats says, noting the cool shade provided by overhead trees and the Las Virgenes Road overpass. Amphibians like slow-flowing water, and their larvae feed on algae growing in pools such as this one.

But a second scoop through the water still reveals no amphibious life.

Instead, Kats dumps the net into his hand and produces a pair of baby crayfish--another nonnative species that feeds on amphibian larvae. How the crayfish, a species native to the Southeastern U.S., turned up in a creek on the West Coast is anybody’s guess. Kats speculates the crayfish arrived via bait shops that sell the crustaceans to sportsmen.

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As Kats rakes through the mud at the bottom of the creek, he notes the absence of aquatic insects, which form the foundation of nature’s food pyramid. He says such native insects have virtually no defense against nonnative predators.

“This water should be covered with tadpoles,” Kats says. “In terms of biodiversity, this habitat has very little.”

Kats has studied the effects of nonnative predators on the newt population in 10 Santa Monica Mountains streams. In three of those--Trancas Creek, Malibu Creek and Topanga Creek--newts have all but disappeared, he said. These are the same streams recently populated by mosquito fish, crayfish or both.

A few miles east, at Cold Creek, Kats offers a striking contrast. There, tree-frog tadpoles cling to rocks in crystal clear water. Water bugs scramble across the rippling surface.

Kats reaches into the stream and scoops up an example of biodiversity: stone fly larvae, dragonflies, a small beetle with pincers like small scissors and a caddis fly larva that bores through leaf fragments and wears them like a dress. Kats even finds several baby newts, still reliant on their gills.

Many Santa Monica Mountains streams looked like this before the introduction of foreign predators, Kats says.

“Crayfish and mosquito fish could be a problem for salamander populations,” said John Brode, a senior amphibian researcher at the Sacramento office of the state Department of Fish and Game. “It’s not legal to release anything like that into the wild, but it gets done all the time--regulations are only good as long as you can enforce them.”

Brode said Fish and Game officials consider California newts a “species of special concern,” but he doubts that the agency would police Southern California creeks for mosquito fish.

“A lot of these introductions [of nonnative species] took place a long time ago,” he said. “There’s probably not much we can do, now.”

Wake, one of the world’s foremost amphibian researchers, said the California newt is only a local portent of a global decline of amphibious populations. The problem was addressed last week at the third International Congress of Herpetology in Prague, which was attended by Wake and 1,000 of the world’s other leading amphibian scientists.

“Over 20% of the presentations dealt with declining amphibians,” Wake said.

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He cited several examples from around the world: The golden toad of Costa Rica--a bright orange rain-forest dweller that mates once a year in a spectacular 72-hour orgy--literally disappeared overnight in 1988. About 20 other species of amphibians quickly followed suit, Wake said.

In Panama, researchers are alarmed about a protozoan--a microscopic, single-celled animal--that causes frogs’ skin to harden, making it impossible for them to breath. Wake described how thousands of dead frogs sit like statues along rivers, suffocated by their own skins.

Amphibians are also dying out at alarming rates in several U.S. national parks, including Yosemite, Sequoia and Lassen.

“In evolutionary terms, amphibians are old,” Wake said. “That means they have survived all kinds of things--climate changes, volcanic episodes, glaciation . . . and here they are checking out on our watch.”

Amphibians are important, he said, because “presumably what could affect them could affect us. They are harbingers of our own fate.”

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California Newt

Taricha torosa

Introduced predators and loss of shade because of wildfires in the Santa Monica Mountains--once home to a thriving California newt population--have led to the decline of this amphibian.

* Size: 5--8 inches

* Behavior: Most likely to be seen on cool, wet days. Breeds December to may. Female lays one or two dozen eggs on aquatic plants or below forest litter. Aquatic larvae become air-breathing when they reach 2.25 inches usually in the fall or following spring.

* Habitat: Near quiet ponds, streams and lakes in oak and pine woodlands. Found locally in Malibu Creek, Cold Creek and Trancas Creek.

* Range: Coastal California from San Diego to Mendocino County, also on western slope.

Sources: “The Nature of California”; The Audubon Society Field Guide to North American Reptiles & Amphibians.