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Entries in exotic species (216)

Wednesday
Jan182017

New Invader in Great Lakes: Thermocyclops Crassus

It's not much to look at. In fact, it's impossible to see without a microscope.

But for the first time in a decade, an exotic aquatic species has been found in the Great Lakes. That makes 185 or 186  non-native species, depending on who's counting, now established in the basin. Some, including the lamprey and alewife, migrated up the St. Lawrence Seaway, but most, including the zebra mussel as well as this latest, probably were introduced via ballast water from ocean-going ships.

Thermocyclops crassus, a type of zooplankton, was discovered in water samples taken from Lake Erie by limnology technician Joe Connolly of Cornell University.

“It’s kind of like looking for a needle in a haystack,” Connolly said. “I didn’t know what it was, but I knew it wasn’t something we’d seen before.”

He found both male and female specimens in low numbers, but enough to say that an established population exists of the invertebrate that is native to Europe, Asia, and Australia. Officials from both the U.S. and Canada have planned more sampling to determine how widespread this new invader is and what its impact may be.

 “We don’t know enough yet about what this species could or could not do in the Great Lakes,” said Elizabeth Hinchey Malloy, an environmental scientist with the U.S. Environmental Protection Agency.

Size isn't an indicator of impact, as the zebra mussel, a fingernail-sized shellfish, and the round goby, a small bottom-dwelling fish, have proven.

Confirmed in 2006, the bloody red shrimp was the last previously discovered invader. It now swarms in excess of 135 individuals per square foot.

"The impact of this species on the Great Lakes is yet unknown, but based on its history of invasion across Europe, significant impacts are possible," said Wisconsin Sea Grant Institute. "The bloody red shrimp is an omnivore. Its diet includes waterfleas and algae. They may compete with young fish, while providing food for larger fish. The invasion of this species in some European reservoirs has been documented to accelerate silica cycling, resulting in blooms of diatoms and, in some cases, plating out of silica onto pipes."

Friday
Jan132017

Zebra Mussels Threaten Popular Connecticut Bass Fishery

The largest reservoir in Connecticut and one of its most popular bass fisheries is at risk of infestation by zebra mussels.

"They're not on in Candlewood yet, but they're right on our doorstep," said Len Greene of FirstLight Power Resources, which owns and manages the lake and a hydro power station on it. "It was only a matter of time before they migrated there."

"There" is the station's foundation on the Housatonic River and nearby boulders. In 2009, the invasive mussels were found in nearby Lakes Lillinonah and Zoar and in the river itself.

And the threat lies in way that power is generated, by pumping water between the lake and the river. In the past, FirstLight has voluntarily limited pumping during times when mussels reproduce to lessen the threat, and plans to continue doing so.

"We've been able to buy five years with the pumping restrictions," Greene added. "It's an unfortunate situation that I think was inevitable at some point, given that zebra mussels spread everywhere they can."

As officials try to decide on the best way to repel a zebra mussel invasion, Candlewood Lake Authority has suggested  a smaller than normal winter drawdown to reduce the risk when the lake refills with river water. Typically, water is drawn down 6 1/2 feet to knock back another invasive, Eurasian watermilfoil. Executive Director  Larry Marsicano added that the authority can monitor the area around the intake pipe.

"We're still trying to manage the risk of them getting a toehold," he said. "Even if one gets pumped in, it takes two to tango."

Aside from the threat that they post for blocking water intakes with their dense colonies, zebra mussels also improve water clarity as they feed on algae and plankton. That would allow for more light penetration, encouraging already problematic watermilfoil to grow faster and spread into deeper water.

Wednesday
Jan042017

Record 'Atomic Sunfish' Caught in Florida

Freshwater fishing in South Florida is unique. Largemouth bass share canals and small lakes not only with peacock bass, but with many of their smaller cousins from Central and South America.

Using a lipless crankbait in a Collier County canal, Jonathan Johnson recently established the first state record for one of the latter, a 2.37 pound Mayan cichlid.

“I looked up the record about six months ago and saw that it was vacant,” said Johnson. “I have caught hundreds of Mayan cichlids but only a couple that I thought were large enough. I was targeting them specifically that day and caught about 25, this being the largest one by about half a pound."

The Florida Fish and Wildlife Conservation Commission (FWC) made the Mayan cichlid, a nonnative species from Central America, eligible for state record status in 2012. But the record has remained vacant until now.

It was first reported in Florida in the early 1980s. During the mid-1990s, the fish began expanding its range and has become common throughout south Florida’s freshwater lakes and canals. Both local and out-of-state anglers target the now-popular fish. Its bright red coloration and scrappy disposition when caught prompted FWC biologists to nickname it the “atomic sunfish.”

In fact, the Mayan is equivalent of a bluegill or crappie in more ways than one. Neither largemouths or peacocks are true bass, but the largest members of fish families with lots of relatives, cichlids for the former and sunfish for the latter. Another of the peacock's cousin, the Oscar, is the No. 1 fish caught in portions of the Everglades and the No. 2 fish sought, behind largemouth. Although reputed to grow to a weight of 3 pounds or more, the state record is 2.34 pounds, caught in 1994 in Lake Okeechobee.

The state record butterfly peacock bass, meanwhile, weighed 9.08 pounds, and was taken in Kendall Lakes during 1993.

Following thorough study to determine that this subspecies of peacock would have little impact on the largemouth population, it was intentionally introduced into the canal system around Miami in 1984. Biologists hoped that it would join the bass in gobbling up smaller cichlids that had been released by irresponsible aquarium owners and could threaten native species via their sheer numbers. While doing just that, it also provides an increasingly popular sport fishery.

Many of the 34 species of nonnative fish now established in Florida are cichlids, including the jaguar guapote. As with the Mayan, FWC requires a minimum of 2 pounds to qualify for a state record.

Fortunately, none of these invaders seemed to have caused major disruptions in native ecosystems "or reduced harvest of native sport fishes," said the FWC. But it encourages anglers to keep all cichlids that they catch, except for the legally-introduced peacock.   

"Most exotic fishes provide excellent table fare," the agency said. "In addition, releasing fish from aquariums or moving them between water systems is illegal and could produce detrimental effects."  

Thursday
Dec082016

Snakehead a Concern in Arkansas, as Well as Potomac

Although the Potomac receives most of the notoriety for its snakehead population, some Arkansas waters have them as well. And that has prompted Arkansas Game and Fish Commission (AGF) to begin a new monitoring program that it hopes will help keep the population in check.

"We need to refresh our information on exactly what species are in these areas and what the population dynamics are before the snakehead populations grow to cause any sort of impact," said Jimmy Barnett, AGF aquatic nuisance species program coordinator." "These baseline data will be critical in future management of the fisheries and the fight against invasives."

According to Barnett, biologists are concerned about the possible impact that the exotic predator is having on bass and other native fish. To find out what is going on, the agency will conduct in-depth fisheries profiles of about 40 sites in eastern Arkansas.

Back in the spring of 2008, a breeding population of northern snakeheads was found there in ditches and near an irrigation pump. Worried that they would spread into waterways connected to the White, Arkansas, St. Francis, and Mississippi Rivers, resource managers quickly applied rotenone, killing about 100 of the invasive predators and collecting 55 specimens for live study. AGF also  attempted to eradicate the fish with  the Piney Creeks drainage near Brinkley. But occasional reports still surface of someone catching or seeing a snakehead there.

"Snakeheads have spread slowly since their introduction, but the last three years in a row, we've seen them expand their range," Barnett said. "They once were only found in one of our fisheries districts, but now we're seeing them reach out to the edges of three other districts."

Barnett says the recent prolonged flooding in east Arkansas and the drainages connecting the White, Cache, and Arkansas Rivers may have increased the speed at which the species has spread.

"There have been a lot of sloughs and ditches that have had water in them for a longer period of time that could have helped the species reach new areas," Barnett said.

Anglers can help in the fight against snakeheads by continuing to kill any they catch and reporting them to the regional AGF office nearest the body of water where it was found.

"People should take a picture of the fish for positive identification, and try to keep the fish until they've talked to a biologist about it," Barnett said. "A native species, the bowfin, looks similar to the snakehead, so we want to verify these sightings to help paint an accurate picture of the species' expansion."

Snakeheads likely were introduced into Arkansas waters by a fish farmer, who intended to raise the exotic fish commercially before their possession became illegal. Upon the advice of state and federal officials, he decided to kill the fish by removing them from his ponds and dumping them on levees. Unfortunately, snakeheads can live for several hours out of water and even crawl to water, which probably is what happened.

Saturday
Dec032016

New State Record for Florida: Mayan Cichlid

Florida has a new state record fish, a 2.37-pound Mayan cichild. Jonathan Johnson caught the fish in a Collier County canal on a lipless crankbait, and says that his record catch was not by accident.

 

“I looked up the record about six months ago and saw that it was vacant,” said Johnson. “I have caught hundreds [of Mayan cichlids] but only a couple that I thought were large enough. I was targeting them specifically that day and caught about 25, this being the largest one by about half a pound,” he said.

 

Johnson took the fish home where his scale confirmed that it was eligible for the vacant state record, which had a minimum submission weight of 2 pounds. Johnson then called the Florida Fish and Wildlife Conservation Commission (FWC) offices to get his record fish certified.

 

With one state record in his pocket, however, Johnson is not resting on his laurels.

 

“I am also targeting the blue tilapia and peacock bass records, but since I use only artificials it will be a challenge,” he said.

 

The FWC made the Mayan cichlid, a cousin of the peacock bass and nonnative species from Central America, eligible for state record status in 2012. But, the record has remained vacant until now. It was first reported in Florida in the early 1980s. During the mid-1990s, the fish began expanding its range and has become common throughout south Florida’s freshwater lakes and canals. Both local and out-of-state anglers target the now-popular fish using methods similar to those used for sunfish. The bright red coloration and scrappy disposition of the Mayan cichlid when caught caused FWC biologists to nickname it the “atomic sunfish.”

 

There are 34 nonnative freshwater fish species that have become established in Florida. Although these species have not caused major disruptions in native ecosystems or reduced harvest of native sport fishes, the FWC strongly encourages anglers not to release them (except legally-introduced peacock bass and triploid grass carp). Most exotic fishes provide excellent table fare. In addition, releasing fish from aquariums or moving them between water systems is illegal and could produce detrimental effects.

 

To properly certify a new Florida state record, a FWC biologist must identify the fish species and witness its weighing on a certified scale. Anglers can check the current state records at BigCatchFlorida.com by clicking on “State Record,” and should notify the nearest FWC regional office if they believe they have caught a record fish. Contact information for FWC regional offices can be found at MyFWC.com/Contact by clicking on “Contact Regional offices.”