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Entries in exotic species (199)


Asian Carp Already Damaging Fisheries

Leaping silver carp on Illinois River. Photo by Nerissa McClelland, Illinois Department of Natural ResourcesMost bass anglers realize that Asian carp pose a threat to the nation's sport fisheries. But they know that because of what they have read and heard, not because of what they've seen and experienced. For them, the danger is theoretical, especially since most of the focus has been on possible consequences to the Great Lakes  if/when these large and prolific exotics gain entrance there.

Bighead and silver carp, however, already are damaging bass fisheries and showing up in frightening numbers in others. In southern Illinois, Kentucky, and Tennessee, the invasion has begun and casualties are mounting.

"Once you needed 12 to 20 pounds to win a tournament on the Kaskaskia (Mississippi River tributary south of St. Louis)," said Rick Brynes, who runs the Angler's Choice Tournament Trail. "But now that's gone, and we're starting to see the same thing on the Smithland Pool (Ohio River). During the past three to four years, the weights have dropped dramatically.

"It's a crisis, and not enough anglers see it," added the Illinois fisherman who has been pressing officials and agencies for action and sounding the alarm to everyone who will listen. "We're going to lose our fisheries. It's just going to take longer in some places than others."

Juvenile Asian carp. Photo by Ben DuncanIn Kentucky, guide Jim Perry said that "zillions" of young-of-the-year carp are showing up along the shorelines below both Kentucky and Barkley dams. "Plus there are schools of them above those dams all around the intakes, where the water goes down to the generators," he added.

Steve McCadams, another guide, added crappie anglers are worried about carp eating up all of the zooplankton and algae that young-of-the-year typically feed on. "Our overall crappie fishery has experienced some declines the last few years as to catch rates and recruitment," he said.

Kentucky fisheries chief Ron Brooks pointed out that little data exists regarding the impacts of Asian carp on native species.  "We have ancillary information concerning their effect on paddlefish," he said, adding that Illinois has evidence of harmful impacts to buffalo, and pelagic sport fish, such as sauger, in the Illinois River.

"We also are seeing fewer shad and skipjack in our tailwaters in western Kentucky," the fisheries chief said. "The real problem with measuring impacts of Asian carp in fertile waters is that they may be very subtle until a certain point of density is reached when a system is finally depleted, or nearly depleted, of algal and invertebrate forage. We are hoping to avoid reaching that threshold."

Arguably thresholds already have been reached on portions of the Missouri and Illinois Rivers, where net sampling has revealed Asian carp now comprise more than 95 percent of the biomass. In other words, those waters contain less than 5 percent native species by weight. Notorious for leaping when frightened, the silver carp also has made boating hazardous in these places, especially in the Illinois River below Peoria.

Riverine fish in their native China, silver and bighead carp spread in every direction after escaping Mississippi Delta aquaculture facilities because of flooding during the 1970s. Prolific, voracious, and fast-growing, they overwhelmed those Midwest waters first. They did so by gobbling up phytoplankton and zooplankton, which is critical forage not just for shad, paddlefish, and buffalo, but for fry of sport fish, including crappie and bass.

"Between 1994 and 1997 commercial catches of bighead carp in the Mississippi River increased from 5.5 tons to 55 tons," reported the Tennessee Wildlife Federation. "Today, commercial fishers in the Illinois River regularly catch up to 25,000 pounds of bighead and silver carp per day.

Asian carp harvested from Kentucky Lake. Photo by Jim PerryAnd while most attention was focused on the fear that the invaders might migrate into the Great Lakes via a manmade connection between Lake Michigan and the Illinois River, they quietly pushed east into the Ohio. That gave them entrance to the Tennessee River and Kentucky Lake, as well as Lake Barkley and the Cumberland system. Now, their numbers are exploding in those reservoirs, even as they have been found as far up the Cumberland as Old Hickory and as far up the Tennessee as Watts Bar.

"Personally, I think it's too late to fully save the Mississippi and Ohio Rivers. The quantity of carp in both those rivers is unimaginable, although, sustained fishing does help," said Ben Duncan, a commercial fisherman, as well as high school mathematics teacher. "If we don't start soon, the Tennessee and Cumberland Rivers will soon follow."

Duncan added that he already sees how native fish have changed their behavior because of the carp invasion. "I think it's even influenced the crappie population and spawn on Kentucky Lake," he said. "Commercially, we catch way fewer fish in the bays than we did seven to eight years ago, especially buffalo, a fish that competes with Asians for food."         

Even more concerning, they are growing to sizes never before seen, even in their native China. Earlier this year, Bill Shroeder foul-hooked and landed a 106-pound silver carp in Kentucky Lake. Fisheries experts say the maximum weight for that species should be about 60 pounds.

What's being done to protect sport fisheries in these imperiled waters? Not enough, stressed Byrnes, who has pressed the U.S. Geological Survey (USGS), the U.S. Fish and Wildlife Service, and other agencies to explain why they are not more aggressively exploring and implementing strategies to manage Asian carp.

"Things could be done to eradicate them that are not being done," he said, adding that lack of funding seems a contributing factor.

"We're 25 years into this, and we need some action now," the Illinois angler said. "Asian carp can take over and change our fisheries forever."


While resource agencies aren't responding to the Asian carp threat as quickly as some would like, they are working on control methods, according to Michael Hoff with the U.S. Fish and Wildlife Service.

"It is unlikely, in my experience, that any technology will be the end all," he said. "That is why we, in the U.S. agencies, are researching and developing a variety of containment and control technologies that are feasible now, and may be implemented within the next few years."

Any strategies, he added, must take into account "a variety of scientific, social, political, and environmental constraints."

Genetic modification is one option. It would require stocking hundreds of thousands of altered carp to breed with the existing population to cause reproductive failure, reduced fertility, or ineffective recruitment. But concerns about  the effects of genetically modified animals on the environment and humans makes this option less likely. Variations that do not require modification of the nuclear genome also are being explored, but they likely would work only where densities are low.

Distribution of "microparticles" that only silver and bighead carp would eat seems a more likely strategy.

"Those microparticles are being developed to kill only Asian carp," Hoff said. "I am hopeful that the microparticle technology will be approved for use within the next several years."

Photo by Nerissa McClelland


As research continues on methods to control Asian carp populations, Kentucky and Tennessee have followed the lead of Illinois in promoting commercial harvest. The mild-flavored fish is highly prized for food in Asian, and slowly is growing in popularity in the United States. Additionally, meal made from carp can be used in livestock food, as well as fertilizers.

Kentucky fisheries chief Ron Brooks said that Riverine Fisheries International, LLC has retrofitted a salmon processing ship to accommodate carp and now is towing it to his state from New Orleans. "The owner has a very aggressive plan of attack concerning fishing the carp and expects to eventually haul in about 150,000 pounds of Asian carp daily," he said, adding that he knows of at least two other processors.

"The good thing about the larger companies is their interest in Asian carp in Kentucky and Barkley Lakes," Brooks added. "The carp grow faster and are more robust in those reservoirs than they are in the rivers. They pose immediate threats not only to the fisheries, but boaters as well."

Tennessee, meanwhile has no major processors as of yet, but the Tennessee Wildlife Resources Agency (TWRA) "proposes to use commercial fishing methods to remove large volumes of bighead and silver carp in established populations such as Kentucky, Barkley, and Cheatham Lakes."

First, a few carp will be caught and then tagged.

"Silver carp tend to stay in large groups so biologists could track the tagged fish to larger groups of silver carp," it said. "Biologists or commercial fishermen could then set nets in areas of known silver carp concentrations and remove them."

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


National Policy Needed to Help Stop Spread of Grass Carp

This grass carp was illegally stocked in a lake where it wasn't needed, and the health of the fishery has suffered as a consequence. Photo by Robert Montgomery

Although grass carp have been found in every one of the Great Lakes except Superior, resource managers don’t believe that the exotic fish have established a self-sustaining population.

But the Mississippi Interstate Resource Association (MICRA) recently warned that “state grass carp regulations are varied and inconsistent, and a national policy strategy is needed to effectively minimize the risks of additional fertile and sterile grass carp introductions into the Great Lakes.”

MICRA reached that conclusion as result of a study funded by the U.S. Fish and Wildlife Service (FWS) to look at grass carp use, production, and regulations. It also made recommendations to help minimize risk not only to the Great Lakes, but other waters not yet infested by unintentional introductions of this aquatic invader.

Those recommendations include the following:

  • Production, shipment, stocking, import, and export of diploid (fertile) grass carp should be prohibited except by licensed facilities.
  • States that allow production of triploid (sterile) grass should develop a set of minimum standards, permit requirements, and recordkeeping for diploid broodstock.
  • States that allow importation of triploid carp should adopt consistent regulations that allow only FWS-certified fish.  Also, increase random inspections and enforcement of regulations in these states.
  • FWS should work with states, producers, and other partners to develop testing procedures for quality controls and law enforcement in support of random inspections.

Grass carp, a species of Asian carp, were first imported into the U.S. in 1963 as a tool to manage nuisance aquatic vegetation, including exotic hydrilla, in ponds and impoundments. But flooding allowed many to escape into rivers and streams and, by 1970, they were reported in the Mississippi River basin.


Snakeheads Growing Bigger, Spreading Farther Up the Potomac

Dan Moon caught this monster snakehead on a Booyah spinnerbait.

As state and federal resource managers revealed that the northern snakehead has spread into the Upper Potomac River, a local angler provided yet more evidence that these exotic predatory fish grow larger here than anywhere else in the world. That's a potential double whammy for bass and other native species.

"Part of the reason we should be worried about it is we don't really know what the impacts are going to be," said Joe Love, tidal bass program manager for the Maryland Department of Natural Resources (MDNR). "We do know that, in some cases, invasive species cost millions of dollars in damage to the ecosystem."

With the population of snakeheads in the tidal Potomac now an estimated 20,000, one concern  is that  aggressive snakeheads will outcompete bass for food, a fear that is heighted by the fact that they are growing to world-record proportions. In late June, Dan Moon boated the latest giant, which weighed 18.8 pounds on an uncertified scale.  The official world record checked in at 17-12, and was caught last year within two miles of where Moon caught his fish.

With both adult snakeheads and fry confirmed in the C&O canal above Great Falls, it seems almost certain that the invaders will spread up the non-tidal Potomac, as well as into its tributaries.

"Eradication is not possible once these fish become established in an open river system such as the Potomac," said MDNR biologist John Mullican. "We expect that these fish will eventually become a permanent part of the Upper Potomac fish community. Confronting snakeheads in the canal system is the best way to mitigate their emigration into the Upper Potomac.

Consequently, Maryland is working with the U.S. Fish and Wildlife Service and the National Park Service to develop control strategies.

MDNR emphasized that the snakehead can be caught legally in any season and at any size. "We'd like it to be harvested if anyone catches it," Love said. "We'd like it if they took it home and possibly ate it. Anglers and archers enjoy fishing for them, which is great. And they enjoy eating them, which is great."


Hydrilla Creeps Closer to Great Lakes

Hydrilla is creeping ever closer to Lake Erie, the warmest and shallowest of the Great Lakes. Most recently, it has been found about 20 miles away in Lake Pymatuning, a 17,000 -acre impoundment on the Ohio/Pennsylvania border.

"It is a serious situation," said Brian Pilarcik of the Crawford County Conservation District. "It can grow very fast, almost an inch a day and forms large, dense masses that can and will impact water sports and will have a negative impact on tourism in the county.

"We are very concerned that the plant could eventually reach Lake Erie."

An environmental educator at Pymatuning, Linda Armstrong added, "The lakes here get quite a bit of use and people will go from one to another, so it is critical to clean all equipment as well as boats."

Already Pennsylvania resource managers have talked with their counterparts in Florida about the discovery, with the latter promising assistance in containing the invasive plant.

Long a problem for many fisheries in the South, hydrilla was first reported in Pennsylvania during the mid 1990s, according to Pennsylvania Sea Grant (PSG).  It's also now established in Bucks County and the Schuylkill River in Philadelphia. The next closest infestation to Pymatuning is Lake Arthur, about 60 miles to the south.

"Hydrilla is a federal noxious weed that continues to spread to new regions in the United States," PSG said. "It is unknown exactly where hydrilla originated, but Asia, Africa, and Australia are all mentioned in the literature as native ranges.

"Currently, Antarctica is the only continent without records of hydrilla."


Asian Carp Spawn Raises Threat for Barkley, Kentucky Lake Sport Fisheries

Can an Asian carp invasion destroy a world-class sport fishery? We're about to find out. And, no, it won't be in the Great Lakes.

Ground Zero will be Kentucky and Barkley Lakes, where anglers and commercial fishermen now are seeing millions and millions of young-of-the year silver carp.

Commercial fisherman Ben Duncan sent me these photos that he recently took at Boswell Bay, where he caught about 500 of them.

"I've seen similar schools in Cypress Bay, Eagle Creek, and Blood River," he said. "My conjecture is this year's mid-summer flood has made the 2015 spawn one for the record books."

And Paul Rister, a Kentucky fisheries biologist, confirmed that assessment. "Yes, we are aware of the tremendous spawn of Asian carp in the tailwaters and lakes this past spring," he said, adding that the state recently implemented a nickel a pound subsidy to encourage commercial harvest.

He also said that the numbers of carp likely will be far more than commercial fishermen can harvest, especially since nets can capture only larger specimens.

"So, what is the answer?" he continued. "There is not one yet. The good news is that it is still very unlikely that the carp have impacted sport fish in the lakes."

They may have displaced them, though, meaning anglers might find the fishing tougher as they are forced to fish new areas. Also, with so much forage, bass and crappie might be more difficult to catch on artificial baits--- at least immediately after the carp spawn. But within a few months, the fast-growing carp are too large for sport fish to eat.

Those impacts are short term. What's going to happen during the next year? Or five? Will the invasion overwhelm the sport fishery as carp occupy so much water that there's no room for other species?  That's happened in portions of major rivers, including the Missouri and Illinois.

Will commercial fishing contain carp numbers? Will scientists develop a chemical or biological control?

We will just have to wait and see.