Imagine buying 3-inch fish for an aquarium, with no idea that they have the potential to reach the size in the photo above. That happens time after time all over the U.S. when hobbyists buy pacu, which resemble their smaller piranha cousins. They have impressive dentures of their own, but their teeth are flatter and used mostly for cracking nuts and seeds.
And every summer, the consequences of those purchases play out, as anglers report catching pacu released into public waters by irresponsible aquarium owners. For example, this year, two were caught in Michigan's Lake St. Clair and another in the Port Huron area.
Standard response from both anglers and the public in general when this happens is "Well, they wouldn't have survived the winter anyway." In most cases, this is true.
But not always, as I reveal below in a story that I first wrote for B.A.S.S. Times and Activist Angler three years ago.
And one of these days, pacu or piranha, maybe both, just might find welcoming waters where they too can survive in a climate far too cold for them under normal conditions. Those areas might be springs or perhaps warm-water discharges from power plants.
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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.
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.