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Entries in exotic species (190)

Friday
Jul102015

As Predictable as Summer: Another Toothy Exotic Caught in U.S. Waters

Every year, anglers catch tropical pacu, a vegetarian cousin of the piranha, in waters across the United States.  For example, Holley Luft caught a 14-inch specimen in Michigan’s Lake St. Clair last July. They do so because irresponsible aquarium owners release them into lakes and rivers.

And more infrequently, for the same reason, anglers catch one of those fish with the razor-sharp teeth and a reputation for tearing flesh to shreds. That’s what happened late this spring, when Roger Headley pulled a piranha from Arkansas’ Lake Bentonville.

“I about messed my pants,” Headley said.

Arkansas Game and Fish Commission confirmed the catch and a spokesman said the fish was “probably a pet that got too large or difficult to manage.” He added that a variety of exotic species are found in state waters annually, including an octopus in Lake Conway in 2003.

Another piranha was caught at Hickory Creek Marina on Beaver Lake in 2014. Several have been found at Missouri’s Lake of the Ozarks since 2007.

In trying to allay fears, especially regarding piranhas, fisheries managers always are quick to point out these tropical invaders can’t overwinter and reproduce because they are intolerant of cold.

But that is not always the case, as B.A.S.S. Times revealed two years ago. The Jack Dempsey, a tropical predatory fish related to the peacock bass, is thriving in South Dakota’s Fall River. How is that possible?

“The hot springs in the river makes it perfect for cichlids,” Mike Smith, aquatic nuisance species coordinator for South Dakota Game, Fish and Parks, said in 2012. “We first found a Jack Dempsey there in 2009. Then, two weeks ago, we found multiple-year classes.”

“And there’s no way that the fish could have gotten there except aquarium release.”

In that case, the Jack Dempsey’s impact on native species likely will be minimal. Few other predators live in the shallow water, and forage species gobbled up by the aggressive cichlid can be replenished from populations outside the range of the hot spring’s influence.

But the discovery was significant because it confirms that exotics can use thermal refuges provided by springs or warm-water releases from power plants to survive in cold climates. Will pacu be the next South American exotic to find such a hospitable environment?

Or maybe piranha?

Thursday
Jun042015

Less Habitat --- Not More --- Might Help Asian Carp Spread

Who would have believed that you could catch a largemouth bass, or much less a spotted bass, on a 9-inch swimbait? And how about that crazy looking Alabama rig? No way would that work.

But it’s not only in bass fishing that nature constantly reminds of how little we know.

Perhaps the coelacanth provides the best example. The primitive fish was thought to be extinct for about 65 million years when one was pulled from the depths in 1938 off the coast of South Africa. Since then, several more have been caught, including some 6,000 miles from the original location.

More recently, scientists say that they believe that a reservoir 400 miles below our feet contains enough water to fill our oceans three times. If true, this suggests that our surface water actually came from within, instead of being deposited by icy comets striking Earth billions of years ago. It also makes one wonder what the planet would look like if all that water were up here instead of down there. Those who are religious might say it would look much like it did shortly after Noah built his arc--- and they might add that explains where the water came from.

Exotic species, meanwhile, provide some of the greatest--- and costliest--- of nature’s mysteries. And, as speedier transport and improved technology facilitate their spread, they will continue to do so. That’s because the consequences of their introductions can’t truly be determined until it’s too late. Yes, we can theorize based on their size, needs, breeding habitats, etc., and the niches that they filled in their native habitats.

But as we’ve learned in recent years, zebra mussels, Asian carp, and other invaders are not subject to the same limiting factors--- predation, disease, climate, habitat--- as they were in their native ecosystems. In other words, what it was there is not what it is here.

Yes, we knew that zebra mussels would filter the water in the Great Lakes. But we had no idea that this process would contribute to a resurgence in blue-green toxic algae blooms or that the shellfish would link with another invader, the round goby, to cause fish-eating birds such as loons to die of botulism poisoning. Yes, we knew that Asian carp would compete with native species for food and habitat. But we had no idea that the silver would become a serious navigation hazard on some waters because of its leaping when frightened.

Which brings us to a recent revelation by a scientist at the University of Waterloo in Canada. Her proposal turns on its head the idea that Asian carp and other exotic species require an abundance of suitable habitat to thrive and spread. And if she’s correct, that means total lockdown of the Great Lakes from its manmade connection with the Illinois River is more important than ever.

“We recently found that only 10 Asian carp are needed to establish a population in the Great Lakes,” said Kim Cuddington, an ecology professor. “But then we asked, if there are so few individuals initially, how do they find a mate and create an ecological disaster?”

The answer is “landmarking.” And it works this way: Where is it easier for you to locate bass, in a pond with one laydown or a pond with a dozen? Yes, fishing might be better overall in the latter, but that’s not what we’re talking about.

We’re talking about a “hook up” --- forgive the pun--- in a non-angling sense. Whether a lonely male is an Asian carp or a butterfly, he instinctively knows to hightail it to the nearest preferred landmark habitat--- or "hangout"--- of his species to find a mate. This strategy allows species to reproduce even when population densities are low.

"With an endangered species, if the number of landmarked sites is increased, the individuals will have a lower chance of finding a mate," said Cuddington. "By contrast, decreasing the number of landmarked sites in an effort to keep invasive species from reproducing has the opposite effect, and ensures individuals have a near certain chance of finding a mate.”

Asian carp use river water quality and flow rate as landmarks to find mates more easily than originally thought, she explained.

"For species like Asian carp, precautionary measures have to be extraordinary to prevent establishment in the Great Lakes," said Cuddington. "When we see Asian carp use landmarking, officials need to worry."

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

Friday
May222015

Monster Silver Carp Suggests Nightmarish Future Awaits Anglers, Native Species

What will happen to fisheries nationwide and even to outdoor recreation in general as Asian carp continue to spread, reproduce, and outcompete native species? We’ve just received a glimpse of a nightmarish possibility from Kentucky Lake, where angler Bill Schroeder foul-hooked and landed a 106-pound silver carp.

Although I’ve been unable to confirm it, I suspect that’s the largest silver carp taken in the United States, and possibly even the world. Experts say maximum weight for the exotic fish is about 60 pounds. And even now, the Tennessee state record for the silver carp, caught in 2013 on Kentucky Lake, was just 14 pounds, 13 ounces.

What’s going on? Silver carp like it here. So do bighead carp. Typically a larger fish, its maximum weigh is about 90 pounds. But in 2011, an angler targeting paddlefish hooked and landed a 106-pound specimen at Lake of the Ozarks.

And the exotic lionfish likes it here too. As it spreads all across the Gulf of Mexico and up the Atlantic coast, anglers are catching larger and larger specimens of this voracious predator. In its native range, it grows to 12 to 15 inches. Just a few days ago, one was caught off in the Florida Keys that measured nearly 19 inches.

Why are these exotics growing to horror-movie size proportions in our waters? Because they are exotic species, they have no “natural” predators, as they do in their native ranges. And they’re feasting on an abundance of food in our relatively fertile and healthy waters. By contrast, Asian carp struggle to survive in their native range because of pollution and overfishing.

Will the same happen with the Burmese python in the Everglades? Introduced to the wild by an irresponsible and little-regulated pet industry, it is now gobbling up native mammals and reptiles, and likely will expand its range into more developed areas. Will it grow to unprecedented size as well?

Now consider this: Asian carp are schooling fish. Frightened by disturbances on the surface, silver carp often go airborne, striking and injuring anglers and other boaters.

But the fish we see in videos of these airborne attacks usually weigh no more than 10 or 15 pounds. Imagine dozens of 100-pound silver carp taking flight all around you as you motor to your favorite fishing hole.

Of course, no one thought about such possibilities when the carp were imported by aquaculture facilities during the 1970s. And it wasn’t until the 1990s that we really started worrying about them crowding out native species in our rivers.

And then there’s the snakehead . . . 

Tuesday
May192015

Public Outcry Forces Minnesota to Delay Invasive Species Training Program

Following public outcry from resort owners, anglers and boaters, the Minnesota Department of Natural Resources (DNR) will postpone an invasive species training and trailer decal program that was set to go into effect July 1.

In the state legislature, a House committee voted to cancel the law, while a Senate panel has proposed a compromise that would delay implementation and remove charges for the class and decals. As the law was originally enacted, “lake service providers” are required to pay $50 for a three-year permit.

Passed in 2012, the law also requires boaters and others who tow boats and water-related equipment to take classes about how to avoid transporting aquatic invasive species, such as zebra mussels and milfoil, form one water body to another and then buy decals for their trailers to confirm that they have taken the class (usually online).

The DNR supports the education that would be provided under this law, but recognizes there are some concerns with the way the law is currently written,” the agency said. “For example, people transporting boats on trailers through Minnesota to another destination are required to take the course and display a decal even if they don’t put their boat in Minnesota waters.”

DNR Assistant Commissioner Bob Meier added, “With the legislative interest in this educational program and ongoing discussions about possible changes, we are postponing the launch until we see if the legislature acts this session to modify the program.”

State Sen. Tom Saxhaug said, “Education is critical to this whole aquatic invasive species idea. We are not trying to stop tourism in the state in any way, shape or form, but what we are trying to do is to make sure everyone in the state knows how to clean their boats.”

For funding its Invasive Species Program, Minnesota includes a $5 surcharge on watercraft registered in the state and a $2 surcharge on nonresident fishing licenses. Resort owners say current fees and decal requirements already have cost them business. 

Monday
May042015

Lionfish Threat Continues to Spread

As harmful invasive fish species, Asian carp seem to garner most of the headlines, mostly because of the threat that they pose to the Great Lakes.  But the lionfish, a marine invader from the Pacific Ocean, is decimating native species through much of the Caribbean, as well as spreading up the Atlantic coast and across the Gulf of Mexico. (See previous post.)

And now it’s been discovered off the coast of Brazil, which suggests the entire  coast of South America likely will be invaded.

“When the researchers analysed the fish’s DNA, they found that it matched the genetic signature of the Caribbean lionfish population, and not that of specimens from their native Indo-Pacific region. This suggests that the fish may have reached Brazil through natural larval dispersal from the Caribbean, the study’s authors say,” reports Nature.

“But Mark Hixon, a marine ecologist at the University of Hawaii at Manoa, says that ocean currents typically flow in the wrong direction for larval dispersal from the Caribbean to the southeastern Brazilian coast. He says that it is just as likely that the lionfish was brought to Brazil by humans. ‘Lionfish are easy to capture and make beautiful pets,’ says Hixon. ‘It’s easy to imagine boaters carrying lionfish as short-term pets in bait tanks or other containers on their vessels.’”

The Invasive Species Action Network adds this:

“Lionfish are vicious predators that eat any fish or invertebrate they can fit in their mouth. They reproduce easily and the rate at which they have expanded their range shows that they are thriving in this environment. With no predators in our waters they are rapidly impacting many habitats.

“Humans can have an impact. Fortunately, lionfish are very tasty and many restaurants have added them to the menu. In many areas concentrated spearfishing is keeping local populations in check but this is not a practical method of control across their range. In the USA, NOAA is the lead agency on this problem and they are the best source for lionfish information and research.

“NOAA has recently released the draft National Invasive Lionfish Prevention and Management Plan While the plan is still in draft form, it is scheduled to be approved at the next meeting of the Aquatic Nuisance Species Task Force meeting scheduled for the first full week in May.”