Invasion of the Owens River Zipping Along at Snail’s Pace

It’s one of the most spectacular opening days imaginable. The surface of this Eastern Sierra town’s namesake lake is surprisingly smooth, mirroring wispy clouds floating across a bright blue sky.

Making a splash, here and there, are some of the largest trout anyone can remember during a Crowley Lake opener. Thousands of fishermen are kicking off another season in fine style; they can’t ask for anything more.

But then they aren’t aware of the alien invasion in the river that feeds this region’s most popular fishery. And possibly in the fishery itself.

Dawne Becker knows. With dozens of smiling anglers crowded around the cleaning station, methodically carving their fish and stuffing slabs of flesh into clear plastic bags, Becker is picking up discarded carcasses and probing their stomachs in a methodical search for the enemy.

The New Zealand mud snail is that enemy--and it is among us.

“To be honest, it is a little dismaying,” Becker says.

It’s alarming, actually. A fast-multiplying army of the resilient little gastropods, first identified in the Upper Owens River near Benton Crossing last fall, has traveled 5 1/2 river miles and reached the delta above Crowley Lake.

The tiny snails--they’re no bigger than buckshot--cover the stream bed like pepper on salad, Becker adds.

While they aren’t directly harmful to trout, they pose an indirect threat by displacing the more nutritious invertebrates--the may flies, caddis flies and stone flies--that trout and other fishes feed on. They do pose a direct threat, through competition for food, to non-game fishes such as the Owens sucker and speckled dace, and also to native species of snails.

Becker, a Department of Fish and Game biologist charged with monitoring the snails’ progress, isn’t finding them in the fish she’s so carefully inspecting, but she’s reasonably sure they’ve entered the lake. And she is concerned that they’ll turn up elsewhere in the region.

“It’s going to affect the fisheries but we don’t have a good enough handle yet on exactly how great that impact will be,” Becker says. “It’s not going to eradicate fishing, certainly, but those ‘good old days’ people keep talking about, well . . . maybe there was something to that.”

What she means is that the days when large and wild trout were part of the scenery, or so the stories go, may indeed be a thing of the past.

Trout fisheries have endured a variety of hardships in recent years, pollution, destruction of habitat, dams and the dreaded whirling disease among them. The New Zealand mud snail, Becker explains, represents “another straw on the camel’s back” and a heavy one at that.

Indeed, once the snails gain a foothold, they’re difficult if not impossible to control. They’re found throughout New Zealand, of course, but also throughout Europe.

They were first documented in North America, in Idaho’s Snake River, in 1987, presumably having arrived with fish bought by Idaho trout farmers from New Zealand.

Now they’re spreading through rivers and streams in the headwaters of the Mississippi and Columbia rivers. They occupy three major river drainages in Yellowstone National Park--the Snake, Madison and Yellowstone.

Their ability to multiply is astonishing. New Zealand mud snails reproduce asexually: They’re born alive with developing embryos in their reproductive systems. Individual snails have been known to produce litters of 70, and up to 220 snails a year.

In Polecat Creek, a headwater of the Snake River, researchers have found them in densities as great as 500,000 per square meter. More common densities are 100,000 per square meter.

“When you get more than 100,000 per [square] meter, that’s a lot of snails,” says David Richards, a researcher with Montana State University. “There’s not much room for anything else. They’re about as invasive as a species can get.”

Because New Zealand mud snails have the ability to survive out of water for as many as 25 days if conditions are moist enough, they’re easily transported by fishermen and researchers, clinging to their waders and boots. And given their asexuality, an individual snail has the ability to start a new population.

They’ve been documented at depths of up to about 75 feet, in lakes in Europe, and can withstand a variety of habitats, from still water to swiftly flowing streams.

Eradication is impossible without the use of poison--something that will not be used on the Owens River, which supplies Los Angeles with drinking water--or by drying up bodies of water until they perish, although control methods are being researched.

On the bright side, the snails are typically found in high densities only in warmer nutrient-rich waters, not in cold, low-nutrient waters such as the higher-elevation mountain streams.

Meanwhile, state agencies have initiated public outreach efforts, alerting anglers to areas that the snails inhabit and warning them to carefully wash their waders and boots with hot water, and to dry them thoroughly before entering other waters.

Richards, whose focus of study is on the adverse impact the exotic snails are having on native snails, says that the famed Yellowstone wild-trout fisheries “are holding on but not nearly as good as they were” before the arrival of the New Zealand mud snails.

On the Owens River, time will tell how extensive the problem becomes. One local study has shown that while hatchery-raised trout will eat the exotic snails, more wary brown trout are reluctant to do so.

Moreover, the snails are not nearly as nutritious as the aquatic invertebrates they’re displacing, and the snails are even capable of closing up inside their shells and passing through the fishes’ digestive tracts none the worse for wear.

If there’s any good news regarding the Owens River invasion, it’s that it began below the wild-trout section of river so popular among fly fishermen, whose success usually relies on “matching the hatch” of the invertebrates.

But Becker isn’t underestimating the resourceful little crustaceans, and certainly isn’t ruling out an about-face.

“Unlike other snails, these guys will actually face the current and move upstream,” she says. “We’re very concerned, but we just don’t know yet what the effects will be on the recreational fishery. It may be something the average angler won’t even notice.”

NEWS AND NOTES

* Local saltwater: Thursday was the best day of the season at the southern Channel Islands. Anglers on the Aztec out of Pierpoint Landing logged limits of white sea bass and two big yellowtail before daybreak at Catalina; 12 fishermen aboard the First String out of L.A. Harbor Sportfishing caught 56 yellowtail to about 25 pounds and 12 white sea bass. The Top Gun skipper reported a similar day at San Clemente. The only concern is the seemingly shrinking supply of live squid at Catalina, where sport anglers are buying the bait from the squid-boat crews.

* Local freshwater: Poway’s Mike Long last Friday pulled from the depths of Escondido’s Dixon Lake a lake-record 20-pound 12-ounce largemouth bass. The all-tackle world record, which has stood since 1932, is a 22-pound 4-ounce specimen caught at Georgia’s Montgomery Lake.

* Sailing: Roy E. Disney’s Pyewacket, out of Los Angeles Yacht Club, was first to finish the 125-mile Newport-to-Ensenada race, the 73-foot Reichle-Pughe pulling into the Mexican port city just before 4 a.m. last Sunday, after almost 16 hours at sea. Robert McNulty’s Chance was second, almost an hour behind Pyewacket. Of 438 boats entered, 390 finished in winds that averaged an almost ideal eight to 16 knots.

James Madden’s Stark Raving Mad, from Newport Harbor Yacht Club, was the first-place finisher overall, based on a corrected-time handicapping system. Jeffrey Cohen’s Mental Floss, representing Alamitos Bay Yacht Club, was the first multihull to finish, despite a presumed nighttime attack by a torpedo boat.

“When you have been sailing all night you tend to hallucinate,” Cohen explained in a news release. “Instead of torpedoes rushing the boat they were actually a school of dolphins in the fluorescent water.”

* Hunting: A series of public hearings began today in Sacramento to discuss possible regulation of mechanical duck decoys. At issue is whether the so-called “spinning-wing decoys” or “moto-decoys” are giving hunters an unfair advantage. The next meeting is Monday at 6 p.m. at Long Beach City Hall, in the City Council Chambers. Meetings are also scheduled for Redding, Calif., and Oakland.

* Boating: The annual Newport In-Water Boat Show is in progress through Sunday at Newport Dunes and Marina. On display will be the new Novatec 80 luxury motor yacht, selling for a mere $2,650,000; the Fleming 75 ($2,843,305) and Horizon 82 ($2,795,000). The nation’s top sailboat manufacturers and marine accessory makers also are well represented. Admission is $10 for adults and free for children 12 and younger. Hours are 11 a.m.-7 p.m. today, 10 a.m.-7 p.m. Saturday and 10 a.m.-6 p.m. Sunday.

WINDING UP

The DFG announced the 20th birthday this week of its secret witness program called CalTip (Californians Turn in Poachers), which it says has “led to thousands of investigations and convictions” for poaching, pollution and destruction of habitat.

Since 1981, the hotline--(888) 334-2258--has received more than 500,000 calls. A cash-reward program is funded solely by donations, but DFG records show most callers are more interested in justice than rewards.

Last year, of the 3,547 calls, only 35 were from citizens inquiring about rewards.