‘Fishdozer’ May Aid In Invasive Carp Management

• from The Fishing Wire

Clarendon, AR — The Arkansas Game and Fish Commission and U.S. Fish and Wildlife Service’s Lower Mississippi River Fish and Wildlife Conservation Office in Tupelo, Mississippi, recently tested a new method of fish sampling on the White River that may help monitor the fight against invasive carp. The electrified dozer trawl method streamlines two previously used sampling techniques to collect information on the populations of silver and bighead carp, two invasive species the AGFC is working to reduce in Arkansas waters.

Previously, biologists would slowly motor through an area and use electricity to stun fish while simultaneously dipping them from the water using long-handled dip nets. 

“Dip netting those giant carp can be extremely difficult for the person on the front of the boat,” Matt Horton, Aquatic Nuisance Species Coordinator for the AGFC, said. “You also have some variability between how good different ‘dippers’ are that can make it difficult to get consistent numbers between sampling events.” 

The ‘fishdozer’ takes that variability out of the equation. Instead of people using dip nets, a device called a push trawl is lowered into the water. The trawl looks like a blade of a bulldozer that’s been hollowed out and outfitted with a length of netting as a catch bag that flows underneath the hull of the boat. As fish are stunned by the electric field, the boat cruises over them, securing them in the net like a whale swallowing krill. 

According to Jimmy Barnett, Invasive Carp Biologist for the AGFC, the dozer testing was conducted in three different scenarios along the White River to determine its effectiveness in varying aquatic habitats. Researchers are testing the experimental gear throughout the Mississippi River Basin to modify the design and technique to optimize carp capture and identify where it is most effective.

Standardized sampling methods are necessary to estimate fish abundance. Horton says the AGFC and its partners may be able to more accurately measure the effectiveness of carp removal efforts in some bodies of water using the dozer trawl.

The sampling technique doesn’t have immediate use as a fish removal strategy, but Barnett mentions that with some modifications, the tool may have some applications to help control these invasive fish. 

“We performed both active netting with gill nets and the electrified dozer trawl in Cook’s Lake, which lets us compare the two,” Barnett said. “Gill nets produced 200 adult silver carp versus 78 collected with the dozer trawl, but we did see that the trawl collected mostly fish in the juvenile size ranges up to about 8 pounds. We use gill nets that have large webbing to reduce the amount of nontarget fish we catch, so catching carp smaller than 10 to 12 pounds is pretty rare with our current netting protocol. 

“I wouldn’t say this gear is as efficient as other methods for removing carp, but it may provide managers with another tool for monitoring the distribution and abundance of carp and evaluate the effectiveness of control efforts.” 

Visit www.agfc.com/ANS for more information on aquatic nuisance species like invasive carp. 

112-Year-Old Fish has Broken a Longevity Record

By Sean Landsman from The Fishing Wire Scientists just added a large, sucker-mouthed fish to the growing list of centenarian animals that will likely outlive you and me. A new study using bomb radiocarbon dating describes a bigmouth buffalo that lived to a whopping 112 years, crushing the previous known maximum age for the species—26—by more than fourfold. That makes the bigmouth buffalo, which is native to North America and capable of reaching nearly 80 pounds, the oldest age-validated freshwater bony fish—a group that comprises roughly 12,000 species. “A fish that lives over 100 years? That’s a big deal,” said Solomon David, assistant professor at Nicholls State University in Louisiana, who was not involved in the study. In recent years, thanks to more advanced aging techniques, scientists have discovered many species of fish live longer than originally thought—the Greenland shark, for instance, can live past 270 years. Despite the age of fish being a basic aspect of their biology, we often know very little about a fish’s expected lifespan. Carbon dating Before the study authors even aged a single fish, they had a hunch that these fish, which live mostly in the northern U.S. and southern Canada, lived longer than thought. The team removed thin slices of otolith—small calcified structures that help fish balance while they swim—from 386 wild-caught bigmouth buffalo, most of which were harvested by bowfishers. The researchers then used a microscope to count the growth rings on each slice of otolith. Their first counts yielded estimates of fish that live more than 80 and 90 years old. (Related: “Meet the animal that lives for 11,000 years.”) When study leader Alec Lackmann first saw those numbers, he says his reaction was: “There’s no way!”To validate these extraordinary age estimates, Lackmann, a graduate student at North Dakota State University, and colleagues turned to bomb radiocarbon dating, a well-established method that compares the amount of the isotope carbon-14 in animal tissue to concentrations of carbon-14 released in the mid-1900s during atomic bomb testing. The method has been used to age everything from human remains to sharks. They then cross-checked their otolith results with bomb radiocarbon dating and found a match—validating the estimates of a lifespan between 80 and 90 years, according to the study, recently published in the journalCommunications Biology. In total, five bigmouth buffalo surpassed 100 years of age, but a 22-pound female caught near Pelican Rapids, Minnesota, became the 112-year-old record-setter. “She was actually on the smaller end of the mature individuals,” Lackmann notes. Aging population The first 16 fish Lackmann aged were all over 80 years old, highlighting another surprising finding: Many of the fish were born prior to 1939, suggesting a reproductive failure spanning decades. The likely cause of this failure is dam construction, which impedes—or outright blocks—upstream movement to spawning grounds. (See “Rare whales can live to nearly 200, eye tissue reveals.”) Indeed, bigmouth buffalo are often called “trash fish,” because they’re not usually eaten and are erroneously lumped in with invasive U.S. species like common carp. But Lackmann argues “we should move away from that term, because it maligns far too many native species. ”David agrees, saying that it “automatically detracts value from the organism itself,” which, in the case of the bigmouth buffalo, has an important role in maintaining the health of its native rivers—displacing invasive carp. (See the overlooked world of freshwater animals.) Though historically unpopular as a sport fish, the bigmouth buffalo is increasingly a target of bowfishers, which shoot fish with bow-and-arrow, often at night with spotlights. Almost all U.S. states where bigmouth buffalo are found have no limits on sport or commercial harvests. The fish is not considered threatened in the U. S. but is of special conservation concern in Canada. Lackmann and David hope the discovery of the bigmouth buffalo’s amazing longevity will help boost its profile.“I hope that knowing this cool fact about them will have people look at this species more closely,” David says.

Essential Alligator Gar Research Underway in Oklahoma
Craig Springer
from The Fishine Wire

Be not afraid– unless youre a carp or buffalo fish. Alligator gar feed on rough fish photo Richard Snow ODWC

Lake Texoma lies over the Texas – Oklahoma state line. This boundary water is enormous. Denison Dam backs up the Red and Washita rivers for miles. The swollen arms of several tributary streams form massive lake coves that shoulder into the main water body. Consequently, there is much open water and ample shoreline for anglers seeking to catch black basses, crappie, sunfish, blue catfish and white bass.

The striped bass fishery is of good repute. And there is something to say for the alligator gar fishery as well: alligator gar are under-studied.

For anyone with even a perfunctory knowledge of alligator gar, this may seem counter-intuitive—that not a great deal is known about one of the largest freshwater fishes in North America.

Consider this. Alligator gar reach an enormous 13 feet long and fatten to a plump 300 pounds. It’s a long-lived leviathan with some of the eldest individuals swimming this very moment, having hatched when Apollo 10 navigated around the Moon in May of 1969.

These giant fish have a growing, almost cult-like following of anglers, and for good reason. Hook one and hang on. An eight-foot-long alligator gar can take you for a ride. You will see a tail dance in a glistening spray of water akin to a silvery tarpon over turquoise flats in nearshore salt water—except alligator gar potentially have more heft. Get a gator gar to the boat, and with a parting flick of its round tail fin, its sinuous form slips into the murk to be caught again.

Or will it?

That’s a question that Oklahoma Department of Wildlife Conservation (ODWC) research biologist, Richard Snow, seeks to answer.

“Virtually any information we glean from ongoing research is new information,” said Snow from his Norman, Oklahoma, office. Snow is seven years into research into the alligator gar’s life history and has most recently embarked to learn more on a how the fish fairs after being caught and released. The answer to this question is central to sport fishery management and has applicability well beyond the bounds of the Oklahoma state line.

The U.S. Fish and Wildlife Service’s Wildlife and Sport Fish Restoration Program funds Snow’s research—the monies derived from excise taxes paid by tackle manufacturers and then apportioned to state wildlife agencies for essential conservation work such as his.

Snow, an Oklahoma native, has had a years-long personal and professional interest in the fish. He has long enjoyed fishing for alligator gar. He earned a graduate degree at Oklahoma State University in natural resource ecology and management where he researched how to age the fish through its ear bones. The bones, called otoliths, lay down rings much like the cross section of a tree.

Snow says he also earned something else in graduate school. “I have a greater respect for the species—they’re a primitive fish, a swimming fossil that survive from long ago,” said Snow. “They are a remarkable fish—heavily armored on the outside like a tank because their insides are sensitive.”

Now, as an ODWC research biologist, Snow has waded deeper into questions associated with catch-and-release mortality, food preference studies, and growth rates.

Snow set up a hooking study with hefty captive alligator gar held in large ponds at Tishomingo National Fish Hatchery. He catches alligator gar just as anglers do at Lake Texoma and elsewhere, fishing with carp or buffalo fish heads. In the experiments, Snow allows gar to run with bait, played for 30 minutes and brought ashore, examined for noticeable internal injuries such as bleeding or air loss from the vent. The controlled environment allows him to monitor the wellbeing of the fish over a long period to detect effects of hooking that would not otherwise be noted in wild fish. The work is ongoing and results yet to be determined.

Along about May of the year, mature alligator gar move into shallow weedy coves of Lake Texoma and broadcast their eggs that adhere to vegetation. That act is replicated in tanks at the national fish hatchery where he and hatchery staff monitor the young gar.

“Alligator gar have explosive growth in their first year of life,” said Snow. “In the span of only nine days, they go from egg to a larvae with a sucker-disc on its head, and then to a predator. They pack on weight and by the end of the first growing season they’re a foot and half long.”

Alligator gar eat other fish. In examining stomach contents of adult gar, Snow determined that sport fish species make up very little of the diet. Their common foods include common carp, river carpsucker, buffalo species, gizzard shad and white bass.

“These predators typically ambush their prey, but they also actively forage or scavenge their food,” said Snow. “In the heat of the summer when oxygen is low, they gulp air into a highly vascularized swim bladder to ‘breathe.’ Bowfishers and anglers take advantage of these habits to locate alligator gar.”

Snow says the ongoing research will help his agency steer alligator gar fisheries toward sustainability.

Cliff Schleusner, Chief of the Wildlife and Sport Fish Restoration Program, Southwest Region agrees. “These Holocene hold-overs have been understudied and the angler-funded work underway by the Oklahoma Department of Wildlife Conservation adds to a woefully scant body of knowledge,” said Schleusner. “Alligator gar, an apex predator, provide an ecological balance that regulate the populations of other fish species—not to mention an angling experience unequaled.”

— Craig Springer, External Affairs, U.S. Fish and Wildlife Service – Southwest Region

Know the difference: Invasive Carversus Common Carp

Michigan DNR Staff
from The Fishing Wire

There’s a lot of talk around the Great Lakes these days about carp, especially invasive or Asian carp. What about common carp, those monsters of Michigan waters anglers love to battle with fly rods? Are these fish one and the same and what’s the big deal about carp anyway?

The issue can be confusing.

To better understand the important differences, it’s best to start with a definition of what an “invasive” species is.

“Invasive species are those species which are not native to a particular area – in this case Michigan – and whose introduction causes harm or would be likely to cause harm to the state’s economy, human health or environment,” said Joanne Foreman, communications coordinator for the Michigan Invasive Species Program.

Just because a species is not native does not make it invasive.

“Whether fruits, vegetables, livestock or field crops, most non-native species are not harmful and many provide benefits to Michigan, from boosting the economy to beautifying landscapes,” said Nick Popoff, head of the Michigan Department of Natural Resources’ Aquatic Species and Regulatory Affairs Unit. “When it comes to fish, some non-native species beneficial to Michigan through sportfishing enjoyment have included coho and Chinook salmon and brown and rainbow trout.”

Invasive species are those particular non-natives that pose potential harm.

As the name “invasive” suggests, these species can out-compete native species by reproducing and spreading quickly in areas where they have no natural predators, thereby changing the balance of the ecosystems Michigan relies on for recreation, commerce, food and jobs.

Means of introduction

From the emerald ash borer and sea lamprey to rusty crayfish and Eurasian watermilfoil, numerous invasive species have found their way to Michigan, often by interesting means.

Some traveled here in the ballast water of ships. Others escaped from pet stores or were household pets let go into the wild where they adapted to local conditions. Still others hitched rides on planes, trains and automobiles.

In the case of all carp species, they intentionally were introduced to North America.

Common carp

Common carp were brought to the United States during the late 1800s as an esteemed food of European and Asian markets. Native to Eurasia, common carp are found today in the Great Lakes, large inland lakes and reservoirs, small and large rivers, swamps, canals and drains. Many frequent places where water quality is less than ideal.

An increasing number of sport anglers enjoy battling these fish and some charter operators now offer carp excursions.

Common carp average 15 to 32 inches and 4 to 31 pounds. They have triangular heads, blunt snouts and small barbels (fleshy, whisker-like filaments) at the corners of their mouths.

Because they have been widely distributed and their demand as a food source has diminished, common carp sometimes are referred to as a nuisance species. However, they are not considered invasive in Michigan.

Invasive carp

There are four carp species that are described as invasive – bighead, silver, grass and black.

In the 1970s, invasive carp were brought to the U.S. from Asia, primarily to eat algae in the ponds of aquaculture operations located in the South. During flooding events, these fish escaped into the Mississippi and Illinois rivers and have been migrating north toward Lake Michigan.

Because the invasive carp problem is a binational and multistate issue, U.S. federal and state governments are working together with Canada on a resolution.

The U.S. Army Corps of Engineers, in a partnership with state and federal agencies, has erected electric barriers in the Chicago Area Waterway System and a berm in Indiana to try to keep the carp from reaching the Great Lakes.

The Michigan DNR is among the leading agencies advocating for additional efforts to stop the spread of these fish.

The watch list

Michigan maintains a “watch list” for invasive species. Species on the watch list have never been confirmed in the wild in the state or have very limited distribution. If they are encountered, they should be reported as soon as possible.Silver carp, one species of invasive carp, are pictured leaping out of the water after being disturbed by a passing boat.

“Early detection and timely reporting of these species are crucial for increasing the chances of preventing establishment and limiting potential ecological, social and economic impacts,” Foreman said.

Bighead, silver, grass and black carp are on the watch list. They also are “prohibited” invasive species in Michigan.

Prohibited and restricted species

Some invasive species are legally designated by the state of Michigan as either “prohibited” or “restricted,” making them unlawful to possess, introduce, import, sell or offer for sale as live organisms, except under certain circumstances.

• The term “prohibited” is used for invasive species that are not widely distributed in the state. Often, management or control techniques for prohibited species are not available.

• The term “restricted” is applied to invasive species that are established in the state. Management and control practices usually are available for restricted species.

Michigan’s Natural Resources Environmental Protection Act (Part 413 of Act 451) established the list of prohibited and restricted species, which is regularly amended by Invasive Species Orders.

Bighead and silver carp

Of the four invasive carp species on the watch list, bighead and silver carp pose the most concern.

“Bighead and silver carp are spreading to lakes, rivers and streams in the Mississippi River and Great Lakes region. They have been moving steadily north, but are not yet established in the Great Lakes,” said Seth Herbst, a fisheries A bighead carp, bottom, and a silver carp are pictured. These two invasive carp species are of the biggest concern.biologist and the DNR Fisheries Division’s aquatic invasive species coordinator. “These two species like large lakes and connecting rivers, and if introduced would have the ability to adapt to Michigan’s cold winters.”

Biologists expect that if these invasive carp make it to Michigan waters, the fish will disrupt the food chain that supports native fish of the Great Lakes, such as walleye, yellow perch and lake whitefish – which could diminish fishing opportunities for sport and commercial anglers.

“Due to their large size and rapid rate of reproduction, bighead and silver carp pose a significant threat to the ecosystem of the Great Lakes Basin,” said Tammy Newcomb, DNR senior water policy advisor and fisheries research biologist. “Silver carp leap high out of the water when disturbed by watercraft. Boaters can be and have been injured by these leaping fish. Fear of injury could diminish the desire for recreational boating activities in areas inhabited by these fish.”

Bighead and silver carp have eyes situated below their toothless mouths. Silver carp may grow to longer than 3 feet and weigh up to 60 pounds, while bighead carp are even larger – up to 5 feet long, weighing up to 90 pounds.

Adult bighead carp are dark gray, with dark blotches. As the name implies, silver carp are silver colored with white bellies.

Black carp

Black carp are the largest of the four invasive carp species, able to grow to over 6 feet long and weigh more than 150 pounds.

Black carp are the largest of the four invasive carp species. They can be over 6 feet long and weigh more than 150 pounds. These fish have blackish-brown-bluish scales and an almost white belly.

So far, bighead, silver and black carp have not been found in Michigan waters. There is no evidence that these three carp species have colonized or are present in any numbers in the Great Lakes.

Grass carp

“Grass carp have been detected in low numbers in all the Great Lakes, except Lake Superior, since the early 1980s (Lake Erie in particular) and have historically been introduced into waterways for aquatic nuisance vegetation control in some Great Lakes states,” Popoff said.

Grass carp can grow to more than 5 feet long and weigh more than 80 pounds. They have eyes that sit in line with their mouths, or slightly above, and scales that look to be crosshatched.

“In the mid-1980s, a grass carp sterilization program was put in place to reduce the risk of introduced fish reproducing and reaching nuisance levels that would result in detrimental impacts,” Herbst said. “The sterilization program has worked to some extent, but fertile fish are still being captured in locations where only sterile fish introduction is authorized.”

Despite the reduced threat of grass carp, Michigan is still taking a proactive approach with regulations, enforcement, and using a scientific approach to increase the effectiveness of control efforts.

Knowing the difference between common and invasive carp is not as difficult as it might seem at first, once you know the facts.

“Educating ourselves and others on these species can go a long way in the fight against the proliferation of these non-native, invasive species of carp – fish that have the potential to dramatically damage or destroy Great Lakes ecosystems, causing untold losses to Michigan’s economy and world-class natural resources,” Foreman said.

Watch Michigan DNR staff training to catch invasive carp in Illinois.

Report invasive (Asian) carp and get more information on invasive species. Find out more about the history of common carp in North America.