Jack Dempsey---A New Invasive Threat

Tropical Fish in South Dakota Highlights Threat Posed by Exotic Species

 

                                                 (Photo Source: http://fish.netscype.com)

                        This tropical fish, the Jack Dempsey, now is established in South Dakota.

What resource managers long have feared would happen because of irresponsible fish hobbyists has become reality: An exotic species has established itself in a waterway far north of where it should be able to survive.

Earlier this summer, biologists confirmed that the Jack Dempsey, a South American cichlid related to the peacock bass, is reproducing in South Dakota’s Fall River.

How it that possible?

“The hot springs in the river makes it perfect for cichlids,” said Mike Smith, aquatic nuisance species coordinator for South Dakota Game, Fish and Parks. “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.”

Water nearest the springs stays at about 70 degrees year around, which allows the exotic fish to survive brutal South Dakota winters.

In this 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 is 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.

Jack Dempsey and another popular aquarium species, the red-rimmed melania snail, now live in the hot springs of South Dakota's Fall River because of irresponsible aquarium owners. Photo courtesy of South Dakota Game, Fish & Parks.

Could the piranha be the next exotic fish to become established? Or its much larger cousin, the pacu? Every summer, media across the country report catches of both fish in ponds, lakes, and reservoirs. For example, a pacu was caught in Illinois’ Lake Lou Yaeger in June. And at Missouri’s Lake of the Ozarks, piranha captures have been reported several times since 2007.

Fish hobbyists also have contributed to troublesome infestations of plants such as Brazilian elodea, parrot feather, yellow floating heart, and even hydrilla.

“At a lot of our lakes, people just dump their aquariums to get rid of whatever they don’t want anymore,” said Tim Banek, invasive species coordinator for the Missouri Department of Conservation.

Bill Frazier, conservation director for the North Carolina B.A.S.S. Federation Nation, also has seen evidence of aquarium dumping while serving as monitor of water quality for the city of High Point. He thinks the time is long past for directing blame primarily at anglers, especially bass fishermen.

Much of the problem, he insists, lies squarely with aquarium hobbyists and the pet industry that supplies them, as well as with nurseries that sell exotic aquatic plants.

“I haven’t seen a single trace of any invasive (plant) at the ramps, transferred by boat in 28 years,” he said.

“I know the overall perception is that weeds can be spread by anyone with a watercraft. I am not denying this pathway,” Frazier continued. “I just do not believe it as significant as everyone would have you believe.”

The North Carolina water expert has found parrot feather upstream of a submerged roadbed, where boats can’t go. He has discovered water hyacinth just downstream from a farmer’s market that featured the exotic in a water fountain. And he has seen a discarded aquarium underneath a parrot feather infestation, where the shoreline borders a large apartment complex.

“Some time later, a bank fisherman caught a skillet-sized pacu there,” he added.

And while anglers and the fishing industry pay license fees and excise taxes to finance management of aquatic resources degraded by aquatic invaders, these special interests are allowed to escape responsibility for the damage they do.

“This is what we need to be attacking and taxing,” he said.

The North Carolina conservation director added that waterfowl, wading birds, and even mammals can spread plants as well.

“I have seen beavers moving this stuff from decorative ponds to natural lakes,” Frazier said. “I watched a momma beaver taking parrot feather by the truckload from a decorative pond to a stream below --- and her den.”

Water quality expert Bill Frazier found invasive water hyacinth at this farmers market, just a short distance from a river.

Yes, anglers do contribute, transporting plant fragments and --- more likely --- mussels on boats, trailers, and tow vehicles, as do owners of jet skis, cabin cruisers, and pontoon pleasure boats. Resource managers are combating this threat with both mandatory and voluntary boat inspections at put-in and take-out sites, as well as check points at state borders.

“This year alone, nearly 80 infested boats have been stopped on the borders of Idaho, Montana, Oregon, and Washington, most coming from Lake Mead,” reported the San Francisco Chronicle.

In those western states, mussels are considered the primary danger, because they can impede water flow by blocking intakes at major reservoirs.

For much of the country, though, Asian carp are the major concern. They are spreading up the Missouri and Mississippi and east and south in the Ohio, Cumberland, and Tennessee River systems, well as threatening to enter the Great Lakes.

“Asian carp are the No. 1 threat for us,” said Missouri’s Banek. “The floods of 2011 made it worse, and they have the potential to be more detrimental than zebra mussels.”

South Dakota’s Smith echoes that sentiment. “We’re seeing exponential growth in their numbers,” he said.

And while floods have helped bighead and silver carp move into new areas, anglers also might have contributed.

“Most people don’t know how to identify fish,” Banek explained. “In collecting bait below dams, they could be getting juvenile Asian carp as well as shad.”

Uneducated anglers might even unknowingly move adult Asian carp from one fishery to another, as a South Dakota creel survey clerk learned on Lewis and Clark Reservoir.

He approached two young anglers who said that they had fished all day and caught “only one walleye and one salmon.”

That “salmon” turned out to be a bighead carp that the two had caught in the river below the dam, before they moved their boat up into the lake in the afternoon.

The clerk reported that the anglers never had heard of Asian carp.

“This is what we are up against in trying to stop the spread of these fish,” said South Dakota biologist Sam Stukel. “It’s going to take a miracle.”

Bait fishermen also are unknowingly spreading invasive crawfish species. About half of U.S. states and Canadian provinces have restricted use, sale, and transport of crawfish, or are considering doing so because the threat that these invaders pose to native crawfish and the fisheries that they inhabit.

In considering regulations to prohibit the import and sale of crawfish, the Missouri Department of Conservation discovered 25 invasions in its streams. It also learned that 40 percent of anglers surveyed release live bait that they don’t use, more than 50 percent of bait shops sell species not native to regions where they are sold, and 97 percent of bait shop owners admitted or showed that they didn’t know what species they were selling.

“It is important for anglers to understand that any crawfish species moved from its natural range to new water bodies has the potential to become invasive in those new waters and to adversely affect fisheries,” said Missouri biologist Bob DiStefano.

Not surprisingly, the aquaculture industry and Farm Bureau oppose Missouri’s proposed regulations, citing economic hardship for those who import, grow, and/or sell crawfish. In the Mid-South years ago, fish farmers made the same argument in convincing resource managers to allow them to import and sell bighead and silver carp.