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Entries in USGS (20)

Tuesday
Nov292016

Grass Carp: Why You Hate 'Em and Why They Are Needed

Harvest by anglers and bowfishermen has been added as a control measure for grass carp.Anglers have been complaining about grass carp for nearly 40 years. Coincidentally, that's how long fisheries managers have been using the

exotic species as a control for another exotic, hydrilla, along with other invasive aquatic plants.

What's happened recently at Texas' Lake Austin provides a prime example of why they complain. Grass carp released there in 2012 and 2013 have consumed not just the hydrilla, but all of the aquatic plant habitat, which was beneficial for bass and other species. The stocking permit has now been revoked by Texas Parks and Wildlife Department (TPWD), with anglers and bowfishermen encouraged to catch and kill the carp.

"Anglers get angry at us when we stock grass carp, and we understand that," said Dave Terre, TPWD's Management/Research chief, who emphasized that his agency strives to involve fishermen in plans to control invasive plants.

"Everywhere we've used carp has resulted in a complete vegetation community crash," he added. "But it took 10 years for that to happen at Austin. And maybe someday we'll be able to extend that to 20 years. Just three or four years ago, we were promoting the success of grass carp in Austin."

Ten years is a considerable improvement over what happened in the early 1980s. Over the objections of anglers and TPWD, the Texas Legislature authorized the stocking of 270,000 carp into 21,000-acre Lake Conroe. In just two years, aquatic plants were gone, and the long-lived carp kept it that way until the late 1990s.

About the same time, much the same thing happened up in Kansas' Big Hill Reservoir. A heavy stocking of carp "set the reservoir back eight or nine years," said Doug Nygren, fisheries chief for Kansas Department of Parks, Wildlife, and Tourism.

"We regretted it," he added. "It was a wakeup call to be careful."

Yet, there is a flip side to this grass carp decimation story, starting with the fact that Conroe will be the site of the 2017 Bassmaster Classic March 24-26. The impoundment on the San Jacinto River now has not only grass and grass carp, but a first-class bass fishery.

"It's been producing 30-pound stringers all summer long," said Tim Cook, Conservation Director for the Texas B.A.S.S. Nation. "The lake has a significant number of 8-pound fish and I'm expecting that six to ten over 8 pounds will be caught each day. We've had five Toyota Texas Bass Classics on that lake, so anglers know how good it can be."

In short, fisheries do recover, as these controversial exotics remain the best biological method for controlling hydrilla in public fisheries, as well as filamentous algae in private and hatchery ponds. Sadly, though, their use is not a precise science. Inevitably results are cyclical, as they have been at both Austin and Conroe and other impoundments across the country, and often influenced by variables that resource managers have no control of.

Weather is the most prominent. Lower water levels prompted by drought and warmer water courtesy of hotter temperatures combined to power an unprecedented hydrilla growth spurt at Austin, and suddenly 600 acres spread across the 1,600 acre fishery. "It changed the dynamics and threw everything out of balance," Terre said.

Mechanical harvest wasn't an option, because fragmentation spreads the fast-growing exotic. Neither was herbicide, since Austin serves as a public water supply. Additionally, unchecked hydrilla inevitably would impede hydropower generation.

To knock back the plant, the city of Austin's resource managers stocked 33,000 carp from late 2011 through spring of 2013. Contrast that with only 20,000 that had been stocked incrementally for eight years, starting in 2003.

"We could live with 100 acres," said biologist Marcos De Jesus. "But 600 acres was just too much. It was going to cause problems with the turbines."

Terre added, "Anglers sometimes think that we're attacking the habitat of bass. We're not. We know that vegetation is important. But there are multiple users to consider. And grass carp are a tool."

He added that in lakes like Amistad, Falcon, Rayburn and Toledo Bend, with little development, "hydrilla is not a problem for anyone and we don't touch it."

Efforts already are underway to jumpstart aquatic vegetation again at Austin, by growing it in cages, De Jesus said. "There are going to be lots of efforts to restore habitat and to provide more options, with things like brushpiles."

Because it is smaller than Conroe and because state agencies have begun  to partner with other entities, including bass clubs, in recent years to re-establish aquatic vegetation, Terre is hopeful that Austin's recovery will be rapid.

Activist Angler with 30-pound-plus grass carp that was illegally stocked in community lake.Conroe, meanwhile, serves as a model for restoration not only for Austin, but for the nation, with much of the credit going to Seven Coves Bass Club. The B.A.S.S. affiliate spearheaded growing and planting of native vegetation, even as officials continued to combat hydrilla with more stockings of grass carp.

As part of an overall management plan for the lake, the club was awarded a grant for about $45,000 from B.A.S.S. and the U.S. Fish and Wildlife Service to build a plant nursery on property provided by the San Jacinto River Authority. The latter and TPWD also helped finance the effort.

Additionally, occasional harvest by anglers and bowfishermen has been added to the overall strategy for using and controlling grass carp. In 2011, they removed more than 5,000 pounds of carp from Conroe during a tournament.

The event was intended to reduce carp population "to a number capable of preventing re-sprouting of hydrilla but which will allow us and our partners to better enhance important native aquatic vegetation for fish habitat and water quality improvement," said Craig bonds, TPWD's Director of Inland Fisheries.

While habitat initiatives and angler harvest have been added to help control carp and restore beneficial vegetation more quickly, not much has changed in terms of overall strategies for stocking grass carp to keep problematic vegetation under control, said John Biagi, Chief of Fisheries Management for the Georgia Department of Natural Resources.

Two of the most notable are smaller, incremental stockings as opposed to one massive release, and replacing diploid grass carp, which can reproduce in the wild, with triploid, which are sterile and have shorter live spans.  

"And we are learning," said Texas biologist De Jesus. "We're refining the way we monitor the effects of carp on vegetation."

Terre added, "Instead of stocking carp per surface acre, we're looking into doing it per the biomass of the plants. Our goal always is to maintain good aquatic habitat for fisheries."

Other Considerations

Most anglers think about grass carp only in terms the damage that they do to bass fisheries. But they've been used since the late 1960s by aquaculture facilities to keep filamentous algae blooms under control. They still serve that important purpose today, both in hatchery and private ponds.

A disturbing corollary to that, however, is that they also can cause algal blooms, explained Doug Nygren, Kansas fisheries chief. "When they eat the plants, that releases nutrients that can feed those harmful blooms," he said.

At Clarks Hill, meanwhile, grass carp could help save bald eagles, as well as coots, among their favorite prey on that Georgia-South Carolina border reservoir. Researchers say that a toxic cyanobacteria grows on submerged aquatic plants, especially hydrilla. Coots feed on the plants, contract Avian Vacuolar Myelinopathy, and die, as do the eagles that eat them.

"Native plants are coming on and hydrilla seems to be diminishing," said Georgia fisheries chief John Biagi. "We're in discussions with the Corps (of Engineers) on stocking rates. This is a tough one. We don't want to eliminate good habitat, but the eagles have to be considered."

In the Wild

Diploid grass carp are reproducing in Missouri's Truman Lake, and that's just one of many waters where this plant-eating exotic now has sustainable populations, according to Duane Chapman, Asian carp expert for the U.S. Geological Survey.

While Texas reports they are spawning in the Trinity River and Kansas indicates the same for the Missouri, Chapman said, "The Illinois River has a large wild grass carp population."

In fact, he added, they are reproducing in free-flowing waters from Louisiana up into Illinois and Iowa, including in the Mississippi River. And some have turned up on "the wrong side of the (electric) barrier" designed to keep Asian carp out of Lake Michigan. They're also in the Sandusky, a tributary of Lake Erie.

Although some might believe that dams will stop them, Chapman said, "I suspect that when we start looking, we're going to find diploids fairly common above dams."

He added that some believe that silver and bighead carp pose more of a threat to our waterways than grass carp, both because they are more prolific and because data already has revealed how they are outcompeting and replacing native species.

"But grass carp don't require huge populations to have detrimental effects," he said, adding that they could destroy Great Lakes wetlands, re-established through time-consuming and costly mitigation projects.

"Grass carp remove vegetation and they dig, causing destabilization and turbidity," the carp expert continued.

Additionally, diploid grass carp can live nearly 30 years, surviving on very little when plants are scarce. "They just shut down when the food is not there and don't expend energy," Chapman said. "They're just waiting for things to change, and then they gorge."

How did this happen?

"When grass carp were brought into this country by aquaculture facilities in the late 1960s, they weren't worried about security," he said. "The belief was that they wouldn't reproduce."

Sadly, that has proven to be wrong in waters all over the country.

Additionally, while some states now prohibit diploid grass carp, others do not. And anyone can buy them.

"It might be difficult to take them into some states, but it's tough to police that," Chapman said. "States might agree to make diploids less available. But in states like Iowa and Missouri, where grass carp already are all around you, it's not a big issue. There's no downside."

(A variation of this article appeared originally in B.A.S.S. Times.)

Wednesday
Nov022016

Walleye Will Decline as Bass Expand With Climate Change 

Warming winters and waters will encourage largemouth bass to expand their range in northern states, while walleye populations will diminish and retreat, according the U.S. Geological Survey (USGS) researchers and fisheries scientists in the Upper Midwest.

In a recent study about the effects of climate change, USGS revealed that walleye numbers have been declining and bass numbers increasing in Wisconsin during the past 30 years. It added, "This downward trend in walleye populations is likely to continue as climate change will cause lakes to get warmer over time. Researchers identified characteristics of lakes where walleye or largemouth bass were most likely to thrive and found that both species were strongly influenced by water temperature.

"While walleye populations thrived in cooler, larger lakes, largemouth bass were more abundant in warmer lakes."

In other words, what's best for bass is not best for walleye, added Gretchen Hansen, an author of the study and research scientists for the Minnesota Department of Natural Resources."Going forward, we predict that many Wisconsin lakes are going to become more suitable for largemouth bass, and less suitable for walleye."

The trend will be most notable, she added, in smaller inland lakes.

Larger fisheries are not immune, however, with Minnesota's Mille Lacs a notable example. Biologists believe that warming water is a primary reason for walleye decline in this 132,516-acre lake.

But it's not just that the walleye don't thrive in warmer water. Neither do forage, such as cisco, which they rely on to stay fat and healthy. Also known as tullibee, these baitfish seek refuge in the coldest parts of lakes during summer.

"I liken them to sticks of butter swimming around, a pretty fatty fish with high energetic content," said Paul Venturelli, an assistant professor in fisheries at the University of Minnesota.

In looking at 2,100 lakes in Wisconsin, USGS scientists considered not just water temperatures from 1979 to2014, but acreage, depth, water clarity, and historical weather. "Wisconsin's lakes are going to get warmer in the future, but how much warmer they will get varies among lakes," said Luke Winslow, a research hydrologist.

Scientists estimated that the percentage of lakes with conditions conductive to high largemouth bass abundance will increase  from 60 to 89 percent by mid century. In contrast, the percentage of lakes likely to support natural reproduction of walleye is predicted to decline from 10 to less than 4 percent.

On a positive note for walleye, the percentage of lake acreage likely to support natural reproduction should decline by a much smaller amount, from 46 to 36 percent. "Walleye populations in large lakes appear to be more tolerant of warming than walleye populations in small lakes," said Hansen, who added increasing stocking rates could help mitigate the decline.

Monday
Oct172016

Smallmouth Expansion With Climate Change Not All Positive

At a glance,  what's there not to like about milder winters and warmer waters for northern waters?

"Smallmouth bass, a popular recreational species, are expanding their range northward with climate change," said the U.S. Geological Survey (USGS), in reporting on findings that it compiled from reviewing 31 studies across the U.S. and Canada that document fish responses to climate change.

But, it cautioned, "one of the takeaway messages is that climate change effects on fish are rarely straightforward, and they affect warmwater and coldwater fish differently."

For example, an expanding smallmouth population  will result in new species interactions and altered predator-prey dynamics. That will  complicate life even more for coldwater fish species already stressed by milder conditions. Thus, managers will be tasked with both accommodating the desires of anglers who want to catch bass and  maintaining native species.

That means managing not only the fish but "the expectations of the stakeholders for fisheries changing with climate change," said USGS.

Fish most at risk are those living in arid environments and coldwater species, including walleye and trout, as well as prey species that these larger fish depend on for food. "Climate change can cause suboptimal habitat for some fish," the agency said. "Warmer water, for example, can stress coldwater fish. When stressed, fish tend to eat less and grow less."

Other climate change consequences:

  • Increased frequency and severity of droughts, especially in arid areas, will exacerbate the impacts of regulations on water flow and use for fish and aquatic systems, as well as people.
  • Altered migration times for some coldwater species will allow species that never spawned together before to hybridize. Native westslope cutthroat trout in the Rocky Mountains already are hybridizing with rainbow trout, a non-native species.
  • Abundance and growth of some coldwater species will be reduced. Changes in range, abundance, migration, growth, and reproduction already are occurring for sockeye salmon.

“Even though climate change can seem overwhelming, fisheries managers have the tools to develop adaptation strategies to conserve and maintain fish populations,” said Craig Paukert, a lead author and fisheries scientist at the USGS Missouri Cooperative Fish and Wildlife Research Unit at the University of Missouri.

“Thanks to this synthesis, we can see the effects of climate change on inland fish are no longer just future speculation, but today’s facts, with real economic, social, and ecological impacts,” added Doug Austen, Executive Director of the American Fisheries Society.

 “Now that trends are being revealed, we can start to tease apart the various stressors on inland fish and invest in conservation and research where these programs will really make a difference in both the short and long term.”

Friday
Oct072016

What You Don't Know About the Common Carp

Bluegill and bullheads got me started. But long before I became a semi-skilled bass angler,  common carp educated me. They pulled drag. They broke line. They made my heart pound and my pulse race. And one of them stole my Johnson spincast outfit as it rested in a forked stick on a creek bank.

As I pursued them, I learned the benefits of subtlety and finesse and the importance of tying good knots. And I gained valuable experience combating  double-digit carp hooked on Wheaties, dough balls, and worms long before I encountered my first five-pound bass on an artificial.

Many anglers who grew up in the Midwest and Mid-South, where common carp are especially common, shared similar experiences, I suspect.

What I didn't know then and what thousands and thousands of still don't know today is that the common carp also has altered, degraded, and even destroyed sport fisheries in every state except Alaska.  They've been in our waters so long that most just think of them as natives, which they are not.

Rather, they are arguably the most destructive aquatic species every introduced into the United States. But, as the U.S. Geological Survey (USGS) points out, because they have been present in some areas since the first surveys were taken, their impact can't be definitively determined.

Long before political favoritism, poor judgment,  illegal acts, and under-regulated pet and shipping industries led to the introduction and spread of  other exotic fish, including bighead and silver carp, the federal government championed  import of the common carp. A fish native to Asia and Eastern Europe, it had been cultivated as a food fish and water-garden inhabitant for thousands of years.

Pressure on the feds came from immigrants, who could not believe that the waters of their new homeland did not contain carp. Out in California, Julius A. Poppe imported five carp from Germany in 1872, and, four years later, was shipping them by train throughout the country.

"There ought to be one person in every county who would raise choice carp as stock fish to sell to others to fatten for their own tables," he said.

Listening to Poppe and others, the U.S. Commission of Fish and Fisheries began to intensively cultivate and distribute carp in 1877, with state fish commissions soon following suit. Additionally, the carp's ability to live and reproduce in most every water condition allowed it to spread on its own as well.

So, what happened?  First, the common carp did not prove to be the popular food and sport fish that it was in Europe and Asia. By the turn of the century, in fact, fishermen saw it supplanting the fish that they preferred to catch and eat. Additionally, both anglers and fisheries managers noted  that formerly clear lakes and ponds where carp had been introduced were turning  muddy.

That's because the common carp is a bottom feeder, not a filter-feeder like silver and bighead carp. It uproots vegetation, as it sucks in mud and other matter, retaining the nutrients it finds, while spitting out the rest. This increases turbidity, which, in turn, reduces the ability of predator fish to see their prey. It also hinders light penetration, which aquatic vegetation requires for growth. Plus, the USGS said, "There is also evidence that common carp prey on the eggs of other fish species."

Now factor in the carp's productivity. A female can lay up to two million eggs during one spawn, and the young can grow as large as eight inches in the first year.

Of course, bottom-feeding carp were not solely to blame for murky water and declining populations of native fish. Their introduction came at a time when we also were oblivious to the impacts that pollution and land-use practices had on our lakes and rivers.  As much as anything, carp simply took advantage of conditions that harmed native species while allowing them to thrive.

Today, state agencies spend millions of dollars annually rehabilitating fisheries that have been overrun with carp. For example, Kansas recently contracted with commercial fishermen to catch and remove them from Milford Reservoir, the largest impoundment in the state.

"Agency officials hope that removing carp from Milford will improve water quality and reduce the potential for blue-green algae blooms, while also providing benefits to sport fish," said Kansas Department of Wildlife, Parks and Tourism."

Yeah, the common carp is a great "starter" fish. But who knows what bounty that I and many others might have enjoyed as kids if our waters had not been invaded and degraded by them.

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

Wednesday
Sep212016

More Intersex Bass Found--- This Time in Illinois

The more waters that scientists investigate, the more intersex bass they find. Latest discovery is in the Des Plaines River, about 125 miles downstream from here.

In dissecting 51 male largemouth bass, researchers from the Illinois Natural History Survey (INHS) found that 21 had grown oocytes, or female eggs, in their testicular tissue.

“Long-term surveys conducted by the INHS in this region have shown big increases in largemouth bass over the past 40 years since the implementation of the Clean Water Act,” said fisheries biologist Mark Fritts. “It's a dichotomy here because we're seeing a population that has increased dramatically, but we're also seeing this potential problem rising.”

But this part of the river is far from pollution free. Treated sewage from Chicago flows into this area from the Chicago sanitary and Ship Canal. In a 2016 water quality report, the Illinois Protection Agency found 12 out of the 14 segments of the river tested were impaired by contaminants such a fecal bacteria and toxic industrial chemicals.

Pollution seems to be the common thread in other discoveries of intersex bass, both from municipal sewage and agricultural runoff. Specifics are elusive, except for the belief that chemicals acting as "endocrine disruptors" are causing the mutations.  They distort functions that regulate hormones and the reproductive system.

"This is an emerging field of research. We're kind of on the tip of the iceberg," Fritts said. "There are still a lot more questions than answers."

Starting in 2003, scientists with the U.S. Geological Survey (USGS) found male smallmouth and largemouth bass with immature eggs in several areas of the Potomac River. Then they noted intersex smallmouth and white suckers at 16 sites in the Delaware, Ohio, and Susquehanna Rivers in Pennsylvania.  At one site near Hershey, Pa., 100 percent of male bass sampled had eggs.

Of these findings, USGS scientist Vicki Blazer said, "We keep seeing a correlation with the percent of agriculture in the watershed where we conduct a study."

Additionally, studies conducted from 1995 to 2004, revealed  intersex bass in the Apalachicola, Savannah, and Pee Dee River basins of the Southeast.

Just last year, meanwhile, two federal agencies found significant numbers of male bass were intersex in waters of or near National Wildlife Refuges in the Northeast. Eighty-five percent of male smallmouths and 27 percent of male largemouths tested positive, according to USGS and the U.S. Fish and Wildlife Service.