Taking a Bite Out of Weeding Chores

In protected ponds behind a power plant swim the brood fish whose offspring may soon be deployed to rescue the lakes, drainage canals and golf course water traps of coastal Southern California.

Their only job is to swim, eat and, in a furious few days every spring, to spawn with abandon.

These are the dams and sires of the tens of thousands of sterile grass carp that merrily munch the weeds that once threatened to choke the maze of canals and ditches of the mammoth Imperial Irrigation District.

A premium is put on high volume of eggs and super-potency of sperm. Non-producers--male or female--are terminated. The rule is simple: Reproduce or perish.

“If you have a good spawning, you have a good year,” said Michael Mizumoto, who runs the grass carp hatchery for the irrigation district, the government agency that distributes water and power to the Imperial Valley and portions of the Coachella Valley.

Now the irrigation district would like to get into another business--selling grass carp to other areas of Southern California beset by fast-growing aquatic weeds. The price: $10 per fish.

Although grass carp are much praised in the Imperial Valley, they have been much feared elsewhere. Environmentalists have worried that the fish could invade waterways and drive native fish into extinction by devouring their food source.

But the state Legislature has concluded that if handled properly, the grass carp, which is not native to California, need not be a menace.

Under a new state law that took effect Friday, the hefty fish with the big appetite for vegetation will soon be available for regulated use in Los Angeles, Orange, San Diego, Santa Barbara and Ventura counties, as well as Kern County.

That collective sigh of relief you hear comes from municipalities, water districts and golf course managers throughout the Southland--anywhere the battle has been waged against the dread hydrilla plant and other fast-growing aquatic weeds.

Golf course ponds are particularly vulnerable to hydrilla and aquatic assassins such as sago pondweed and Eurasian water milfoil, all of which are part of the grass carp’s diet of choice.

Not for nothing did the California Golf Course Superintendents Assn. wage a three-year lobbying campaign in Sacramento to get approval to broaden the use of grass carp.

“The grass carp are coming, and we’re all very happy for it,” said Tim Barrier, an association board member and president of its San Diego County chapter.

“They’re awesome; you can’t beat them,” said Mike Kocour, golf course superintendent of the Springs Club in Rancho Mirage, where the carp have already been used.

Under the watchful eye of the state Department of Fish and Game, the irrigation district has been using grass carp since the early 1980s to control weeds in its 3,000 miles of canals and drains, which carry water for drinking and irrigation. Irrigation district officials turned to the grass carp in near desperation after concluding that herbicides and mechanical cleaning were not practical.

“You can’t tell a farmer: ‘Sorry, you don’t get any water for a few weeks because we have to close down the canals to clean them,’ ” said Mizumoto.

The Imperial Irrigation District, the nation’s largest agricultural irrigation district, now boasts the only grass carp hatchery in the western U.S., averaging 65,000 hatchlings a year.

Grass carp hatched in the Imperial Valley are already at work in the weed-clogged canals of Mexicali Valley and Calgary, Canada. Sales have been made to Arizona and Nevada. In California, buyers will need permission from the Fish and Game Department.

To let the water world know they have high-quality grass carp for sale, irrigation district officials took an informational display to the recent convention of the Colorado River Water Users Assn. in Las Vegas, which attracted more than 1,000 water wonks from seven states.

The highlight of the display was a life-size cardboard cutout of Mizumoto cradling a grass carp weighing a good 20 pounds. They made quite an eye-catching pair.

On most days at the hatchery, the process of feeding and watching and releasing fish is orderly and unrushed. But for several days in late March, the pace quickens and timing becomes split-second.

The brood males and brood females--about 3 feet long and weighing 40-plus pounds--are removed from their ponds and given hormone injections. The females get three injections, the males one.

When the time is propitious, the males are allowed to nuzzle the females. To give nature a boost, two males are assigned to each female. Fertility records are kept.

The grass carp’s eggs are subjected to 8,000 pounds of water pressure for 90 seconds, four minutes after being fertilized, to ensure that the fish that hatch from them will be sterile. Each fish is later blood-tested to confirm sterility.

California law requires that only sterile grass carp be released, lest they breed indiscriminately and crowd out native species.

A week after hatching, the carp are released into ponds covered with nets to keep marauding birds from dropping in for a snack. The ponds are protected by chain-link fences to thwart human poachers (possession of a grass carp is punishable by a year in jail and a $5,000 fine). By August, most of the carp are 8 to 10 inches long and ready to be released.

State biologists have monitored the grass carp experiment in the Imperial and Coachella valleys and in San Bernardino County to make sure no fertile fish escape. The Fish and Game Department is bullish on the fish with the green back and white belly.

“It’s another tool in the arsenal to fight unwanted vegetation, a very hungry tool,” said Fish and Game biologist Steven Taylor.