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Entries in invasive species (186)

Wednesday
Mar122014

Fish Pass Through Electric Barrier

The last line of defense against Asian carp entering Lake Michigan isn’t impenetrable, according to a new report by the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service.

Fish can pass through the electric barrier unharmed when they get caught in the wakes of barges passing through. And that’s not all. Metal barges can deplete the charge, and small fish aren’t always susceptible.

"Initial findings indicate that vessel-induced residual flows can trap fish and transport them beyond the electrical barriers, and that certain barge configurations may impact barrier electric field strength,” says an interim report based on laboratory and field experiments.

“Additionally, the preliminary (sonar camera) findings identified the potential for small fish (between 2-4 inches in length) to pass the barrier array in large groups, or schools."

The Corps emphasizes that the findings are preliminary, with more work to be done with the barge community and the Coast Guard to see how the barrier can be strengthened.

“There is no evidence that Asian Carp are bypassing the barriers; nor is there any indication Asian carp are in the vicinity of the barriers,” the agency says. “The closest adult Asian carp found in the Illinois River are about 55 miles from Lake Michigan, and no small Asian carp have been observed closer than 131 miles from Lake Michigan.”

Critics point out that water samples taken near the barrier and in a canal on the lake side of the barrier have tested positive for the exotic fish. Plus, poisoning of the canal in 2009 revealed an Asian carp carcass.

Read more here.

(This article appeared originally in B.A.S.S. Times.)

Tuesday
Feb182014

Exotics Take a Bite Out of Wetlands

Nutria photo from Louisiana Department of Wildlife and Fisheries website.

Most anglers know that Asian carp are harming this nation’s fisheries, from the Upper Midwest down to the Gulf Coast and eastward through the Ohio River watershed.

What many do not realize, however, is that other exotics also are doing severe damage. They don’t receive as much publicity because their range is more limited.

But in Louisiana, the nutria, a large rodent, is devouring the wetlands, destroying spawning and nursery habitat for a multitude of important sport fisheries. In fact, the state estimates that damage at any given time is about 46,000 acres, as about 5 million of the web-footed animals with large, orange teeth feed on the roots and stalks of aquatic plants.

Additionally, the giant apple snail also is taking a giant bite out of the wetlands. They’ve been banned from the state since 2012, but that was too late to keep them from becoming a destructive force, courtesy of irresponsible hobbyists who dumped their aquariums into waterways.

“They eat a ton of plant material, anything they can get their tiny little mouths on,” said Michael Massimi of the Barataria-Terrebonne National Estuary Program. “You are converting a water body from one dominated by plants to one dominated by algae.”

Asian carp, tiger prawns, water hyacinth, and giant salvinia also are among the exotic species doing damage to Louisiana’s coastal system.

Some limited good news is that the state’s nutria control plan, implemented in 2002, has lessened the impact of these furbearers, which were imported during the 1930s and promoted as a way to combat water hyacinth and other invasive plants during the 1940s.

Giant apple snails also are gobbling up wetlands.

Still the cumulative effect of these invaders is significant for an ecosystem already under siege. First came decades of habitat degradation and mismanagement, most of it originating from development and water diversions. These actions accelerated erosion and saltwater intrusion, which are crumbling away the equivalent of a football field every hour.

Then came the Deepwater Horizon oil spill and its aftermath, which added to the peril of an ecosystem that is critical for sustaining the food web of the Gulf of Mexico.

Fortunately, the spill also provided impetus for passage of the RESTORE Act, which provides a rare opportunity to restore and enhance the Delta and its wetlands. Guiding that restoration is a multi-state, multi-agency group known as the Gulf Coast Ecosystem Restoration Council.

And a coalition known as Vanishing Paradise is working to make sure that Council members remember the importance of habitat restoration, which can drive and support economic recovery.

“The people, business, communities, and economy of this region are undeniably reliant upon a healthy and productive Gulf, and ecosystem restoration should be the top priority,” said spokesman Ben Weber.

Sadly, passing legislation and creating coalitions will do little to counter the damage already being done by established exotic species, including the nutria and giant apple snail.

But something could be done to lessen the likelihood of future harmful invasions in Louisiana’s marshes and wetlands, as well as other waterways nationwide. Congress needs to strengthen the Lacey Act, which prohibits the import and trade of harmful species.

Here is how bad the problem is: Since the act’s implementation more than a century ago, only about 40 animal groups have been prohibited, and that usually occurred long after they were imported, escaped into the wild, and started doing damage.

By modernizing the Lacey Act, Congress could empower the U.S. Fish and Wildlife Service to first assess the potential risks associated with a species proposed for import before deciding whether to allow or prohibit its trade in the United States. The ineffectiveness of the current law is easily evidenced by Burmese pythons in the Everglades, Asian carp threatening the Great Lakes, and giant apple snails joining nutria in gobbling up Louisiana’s wetlands.

Friday
Feb142014

Electric Barrier Is NOT Stopping Fish

Oh, yeah! That electric barrier is going to keep Asian carp from entering Lake Michigan via a manmade connection to the Mississippi River basin.

Or maybe not.

A video obtained by the Milwaukee Journal Sentinel shows small fish swimming through the electrified water, just 35 miles downstream from Chicago’s lakeshore.

And no one said that the invaders must be adult fish.

“The only thing holding back the Asian carp at the moment is the electric barrier, but few people beyond Illinois politicians, the canal-dependent barge industry, and the Army Corps are buying the idea that the barrier is doing its job. Many worry the agency's continued confidence in this leaky, last line of defense will take a tragic toll on the Great Lakes, the world's largest freshwater system,” said the newspaper.

Thursday
Feb062014

Invasive Species Threat Goes Both Ways

Mostly resource managers have been concerned about Asian carp invading the Great Lakes through a manmade connection with the Mississippi River basin. But exotics already in the lakes also could migrate out and spread into rivers throughout the Midwest, if the electric barrier separating the two systems is not 100 percent effective.

One of those is the Eurasian ruffe, a small perchlike fish that entered Lake Superior during the mid 1980s in the ballast water of European freighters. It then spread to Lakes Michigan and Huron, and, this past summer, researchers found ruffe DNA in Chicago’s Calumet Harbor.

“The Eurasian ruffe is a relatively small fish that produces a lot of eggs and reaches maturity very quickly,” said Lindsay Chadderton, Aquatic Invasive Species Director for The Nature Conservancy’s Great Lakes Project. “They feed from the bottom of the food chain, and they’re going to compete with native and introduced species dependent on the same fauna.”

On the positive side, Illinois officials emphasized that no live ruffe have been captured in the harbor. They said that the DNA could have come from a bait bucket or ballast tanks, not an actual fish.

Still, even the possibility that the ruffe could be poised to spread inland underscores how vulnerable both the lakes and the Mississippi River basin are to invasive species and the need for an effective two-way barrier, according to The Nature Conservancy and other conservation groups.

(This article appeared originally in B.A.S.S. Times.)

Wednesday
Feb052014

Asian Carp DNA Found in Lake Michigan

Lake Michigan now has joined Lake Erie as a fishery where Asian carp DNA has been discovered.

A single positive sample for silver carp was found in Sturgeon Bay this past summer, according to the Wisconsin Department of Natural Resources (DNR), which conducted the research along with the University of Notre Dame and The Nature Conservancy.

The water sample wasn’t screened for the presence of carp DNA until recently. It was collected originally in a search for evidence of Eurasian ruffe, another exotic fish species.

Is the finding cause for concern? That’s debatable. But it is reason enough to begin regular sampling of Sturgeon Bay.

“When we start talking about evidence for Asian carp in a system and the use of DNA, we talk about repeated sampling events and repeated detections,” said Chris Jerde, a Notre Dame scientist.

This latest discovery was from just one of 50 water samples taken in Sturgeon Bay and 282 total from the state’s portion of Lake Michigan.

But Jerde added that if Asian carp DNA were commonly spread by bird feces, boat hulls, and other means besides live fish, other positive samples would be noted from across the Great Lakes.

"We can talk about alternative pathways (for DNA to get into a water body), but we still have thousands of negative detections throughout the Great Lakes and we have one positive here."

DNR’s Bob Wakeman added, “It is what it is. We just need to clarify what it means.”

Despite the discovery of positive DNA in Lake Erie and even a couple of live carp over the years, no evidence has been found of a breeding population.