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Entries in Great Lakes (121)

Thursday
Feb182016

Although Not as Lethal, LMBV Still in Our Waters

Bass infected with LMBV appear normal, unless the disease turns lethal.

For the majority of bass fishermen, Largemouth Bass Virus (LMBV) is out of sight and out of mind, and has been for more than a decade.

But it's not out of our waters.

Is that reason for concern?

Yes. And no.

No, we aren't seeing numerous die-offs related to the virus that occurred for about a decade during the late 1990s and early years of this new century. And there's no reason to believe that's going to happen again. For example, it has not turned lethal in Saguaro Lake, where it was found in 2010. That discovery made Arizona the 19th state to detect the virus in its fisheries since 1991.

But it's still out there, and, yes, it still can kill, as evidenced by a die-off attributed to LMBV at a small Indiana fishery in 2012. It was the first documented in that state since 2001 at Hamilton Lake.

"Although the die-off was disappointing, it was not devastating," said biologist Neil Ledet, who accurately pointed out that nothing can be done to eradicate the virus."But we want to document where it causes fish kills," he added.

About the same time, resource managers reported finding the virus in four West Virginia fisheries.

Two years before, fisheries managers attributed LMBV as the cause for the decline in both catch rates and size of bass caught in Kerr Lake/Buggs Island on the Virginia-North Carolina border. “We’ve seen some declines in the growth rate, and it’s taking longer to catch a 5-pound fish,” biologist Dan Michaelson said. “But the big key has been the increase that we’ve seen in mortality. Since 2004, it’s up 10 percent, and that’s a lot.”

He added that testing also showed LMBV was present in bass in both the Roanoke/Stanton and James River drainages. "We're going to have to look around some more," he said.

More recently, biologists confirmed that northern snakeheads taken from two Potomac tributaries were infected with the virus. That might seem a good end for a bad fish that could cause the decline of bass and other native species.

But as we learned a decade ago, fatalities aren't always a foregone conclusion. In fact, the exotic fish simply could be carriers for spreading LMBV to bass throughout the Chesapeake Bay watershed.

Over the years, the virus has been found in other species as well, but, thus far, only in bass does it sometimes evolve into a fatal disease.

Why that is the case is one of many specifics that we still don't know about LMBV, including its origin, its means of movement from one water body to another, and why it proved fatal so often for about a decade, but since has leveled out to little more than a foot note--- albeit an intriguing one-- in fisheries management.

"The fisheries management community largely ignores it now," said Gene Gilliland, B.A.S.S. National Conservation Director. "It's not the threat it first seemed to be. It did not wipe out bass everywhere. And it's pretty species specific, unlike VHS, so it doesn't get much attention anymore."

By contrast, viral hemorrhagic septicemia virus has caused massive die-offs of several species, including bluegill, black crappie, drum, gizzard shad, and muskellunge, mostly in the Great Lakes. It also has been confirmed in smaller kills of smallmouth bass and walleye, and more than a dozen additional species have been identified as carriers.

VHS seems the most lethal in colder water, which is just the opposite for LMBV. Both are among more than 100 naturally occurring viruses that affect fish, but not warm-blooded animals.

"LMBV was suspected to be a new virus that evolved from a virus that infects amphibians, as I recall," Gilliland said. " Bass had no natural immunity to it so it spread quickly via who knows what means of transport.  It has now runs its course in most places. Although it can be found in many populations, apparently immunities have built up and so far, the virus has not mutated enough to cause additional fish kills.

Still, we have educated guesses regarding the specifics of LMBV, thanks to annual seminars that B.A.S.S. convened until 2004. At those sessions, fisheries experts from around the country shared information and developed strategies for dealing with the outbreak. For example, they theorized that "stressed" bass seemed to be most susceptible and anglers likely aided in spreading the virus by moving fish and/or water in their livewells.

You can read about their findings and conclusions in a "fact sheet" posted at Bassmaster.com.

Sunday
Dec202015

Noise Could Be Way to Slow Spread of Silver Carp

Anglers and other boaters already know that silver carp don't like noise, and arguably that's not a good thing. That's because huge schools of these exotic fish go airborne as they flee the sounds of outboard engines, often damaging boaters and injuring people.

But this aversion to noise also could provide a silver lining in the quest to slow the spread of silver carp, according to scientists with the University of Minnesota-Duluth (UMD) and the U.S. Geological Survey (USGS).    

“Our complex noise findings suggest that certain sounds could be used to divert silver carp away from strategic points on waterways or herd them into nets,” said Brooke Vetter, a UMD researcher and graduate student.

After placing speakers at the ends of outdoor concrete ponds, scientists tested carp response to pure sounds, which resemble a dial tone, and more complex noises. The fish quickly adjusted to the pure tones, never swimming away more than two consecutive times. But they continuously fled the more complex sounds.

Now researchers are testing complex noise as a way to control silver carp in the Illinois River.

“Silver carp threaten many waterways in the Great Lakes basin by competing with native species,” said USGS's Mark Gaikowski. “Understanding silver carp behavior is critical for determining effective techniques to minimize the ecological and economic damage of this invasive species."

Monday
Sep212015

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."

Monday
Sep072015

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.

Friday
Aug212015

Tennessee, Cumberland River Fisheries Threatened by Asian Carp

Most anglers know that Asian carp are overwhelming populations of native fish in portions of the Mississippi, Missouri, and Illinois Rivers. Likely they are aware that the invaders could have catastrophic consequences for the sport fishery if they migrate into the Great Lakes.

And almost certainly they have seen photos of silver carp leaping from the water, like the one above, as they are frightened by passing boats. This iconic shot was taken in 2007  by Nerissa McClelland of Illinois Department of Natural Resources from the chase boat as an electrofishing survey was conducted on the Illinois River, just upstream from Havana.

What most anglers do NOT know is that silver and bighead carp also threaten the Tennessee and Cumberland River systems , along with the world-class sport fisheries in their reservoirs. Most at risk right now are Kentucky and Barkley Lakes, but the invaders are moving steadily upriver from there.

In the October issue of B.A.S.S. Times, I'll have a detailed report on what's happening to these fisheries and what might be done to save them. Following is some insight regarding the problem from Ben Duncan , a commercial fisherman:

"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. If we don't start soon, the Tennessee and Cumberland Rivers will soon follow.

"Using the Cumberland River as an example, the numbers on the Barkley pool are large, while two pools up--- Old Hickory Lake --- catches, while becoming more frequent, are still at manageable levels.

" I have been on these lakes all my life, and spend more time on the water in a year than most people do in 10, and I can already see how native fish are changing their behaviors due to the invasion of carp. I think it's even influenced the crappie population and spawn on Kentucky Lake. Commercially, we catch way fewer fish in the bays than we did seven or eight years ago---  especially buffalo--- a fish that competes with Asians for food. Such large schools of carp decimate the food source so there's no reason to enter the bays. I have observed the same patterns in gizzard shad. 

"Currently, commercial harvest is the only defense. Kentucky and Barkley lakes are two of the most productive reservoirs in the country and it's concerning that Asian carp have made them so vulnerable. There are still several anglers unaware of the severity of the problem and most need to be educated on how tackling the problem is a collaborative effort among all stakeholders."