Lean out of a boat in the Sacramento-San Joaquin Delta, grab a handful of plants or a net full of fish, and you'll haul in a bunch of stuff that doesn't belong there.
The Delta is considered North America's most invaded estuary. About 200 foreign species have taken root here. A new one settles in about every nine months, usually when a cargo ship discharges ballast water or a homeowner dumps his aquarium in a ditch.
Ranging from Chinese clams and Atlantic fish to South American water weeds, they have crowded out native species in many areas. By some estimates, 95 percent of the Delta's biomass, or the totality of its organisms, are not native.
So it is hardly surprising that some Delta residents reacted with alarm last week when the California Department of Food and Agriculture announced it had intentionally added another invader to the mix: Megamelus scutellaris, a South American plant hopper.
The department released about 5,000 hoppers at three locations late in July. It hopes the new bug will take down another invader: water hyacinth, a floating weed that is a longtime irritant to boaters and water users.
"If it works, it would be great," said Candy Korth, owner of Korth's Pirate's Lair Marina near Isleton. "I just keep thinking, 'Oh my God, I hope there isn't unintended consequences from this bug.' How many times in the history of the world has something been introduced and then they realize: 'uh-oh.' "
Indeed, there are many such examples in the Delta. One is the striped bass, introduced in the late 1800s to create a commercial fishery. It remains an important sportfish, but has also become a voracious predator of native fish, including the threatened Delta smelt.
The arrival of the Megamelus hopper in the Delta came with little public notice. State agriculture department officials announced it only after the bugs had been released.
"It did seem to come as a surprise to everybody," said Bruce Herbold, a biologist at the U.S. Environmental Protection Agency and its foremost expert on the Delta's aquatic wildlife. "I would like to have known about it before they went off and released them."
The hopper, only slightly larger than a flea at adulthood, arrived by a very different route than most invasive species.
The U.S. Department of Agriculture spent several years conducting an environmental assessment to learn if the hopper might harm plants other than the target hyacinth.
In testing on dozens of other plants first in its native South America, then in the U.S. the department found the hopper would breed and feed on only a handful of other species, and it was unable to grow to adulthood on any of them.
The hopper works on hyacinth by inserting its needle-like mouth parts into the plant and feeding on its sap. This damages plant tissues, causing it to die.
In other words, officials think the hopper has a "host specific" relationship with water hyacinth. In their native South America, the hopper keeps the hyacinth population in check, and it is hoped the same relationship can be created here.
"I'm impressed they covered the issues I would be concerned with, and the results are encouraging," Herbold said. "They've made a lot of mistakes through history, and come under a lot of scrutiny. So they're a lot more cautious than they used to be."
Hyacinth hard on farming
Water hyacinth is thought to have arrived in the United States in 1884 as a featured attraction at an exposition in New Orleans.
The plant's large, shiny green leaves and bright purple flowers made it a popular ornamental plant in landscaped ponds, and it remains so today.
But the hyacinth quickly spread to natural waters, where it breeds prolifically. Under the right conditions, it completely carpets the surface of Delta sloughs and canals, where it tangles propellers and clogs cooling water intakes on boats.
The plant does not need to attach to the ground but draws nutrients from long roots that dangle deep in the water column. Those roots can draw all the oxygen from the water, creating hostile conditions for fish. They also readily clog the Delta's many irrigation water intakes.
"It's hard on the farming, because if the water hyacinth plugs off the siphons, farmers cannot use their water," said Rick Carter, superintendent of Reclamation District 1601, which delivers irrigation water and maintains levees on Twitchell Island.
California has spent millions of dollars trying to control hyacinth using herbicides and mechanical harvesters. Both have achieved some success in controlling the weed's advance, but only with persistent repeat treatments that cost as much as $1,000 per acre.
The herbicides also raise environmental concerns. The most common employed is 2,4-D, which can be toxic to fish.
A "biological control agent" like the hopper could end up being easier and cheaper, said Lars Anderson, a USDA plant physiologist: Simply release the bugs, let them breed and go to work on the hyacinth until both populations find a new happy balance.
"The goal is not eradication," said Anderson, who is based on the University of California, Davis, campus.
"Typically what you are shooting for is to drop the numbers down to a low level which just cycles with the agent you brought in. You've got two living systems hopefully getting into a relationship at a harmonious level."
Success far from assured
Steve Lyle, a spokesman for the California Department of Food and Agriculture, said the hoppers initially were released in three locations: Whiskey Slough in San Joaquin County, and Willow Creek and Seven Mile Slough in Sacramento County.
Officials will monitor the success of these bugs, he said, before releasing more.
"The first stage is to determine if the plant hopper can establish self-sustaining populations," he said. "It will take several years to determine this."
Success is far from assured.
Several years ago the USDA introduced a different South American insect, a weevil, in hopes of controlling hyacinth. It proved unable to thrive in the Delta's cold winters, although some of the bugs still survive as yet another introduced species.
"Everyone hoped it was going to be the magic bullet that killed the hyacinth," said Andy Giannini, superintendent of Brannan-Andrus Island Levee Maintenance District.
The Megamelus is thought to be more tolerant of cold weather. But Giannini and Carter remain skeptical of new bug introductions, and plan to continue their regular herbicide programs.
Both have found success lately using a chemical called Aquamaster, a version of the common Roundup herbicide approved for use in water.
Carter recently converted a pontoon boot into a floating spray rig for a better vantage point to attack the hyacinth.
"You don't know what these bugs will do at any given time," Carter said. "It's something that's not native to the Delta."