Iowa Public Television

 

Asian Carp




Mike Hawkins: The silver carp are known for their ability to jump out of the water when they are spooked.  Prop noise from a boat or even the hull noise of the boat splashing in the water can cause these fish to jump out of the water.  It's a defense mechanism that the fish have to get away from danger.

These aquatic aerialists are one of four assortments of Asian carp -- grass, black, bighead and the notorious leaping silver carp.  The latter two have proliferated into a hoard capable of decimating native fish populations.  Chinese in origin, the Yangtze River natives were originally imported to the ponds of Arkansas catfish farms in the 1970s to clobber overgrown algae.  Flooding allowed them to escape to confinements and to nearby waterways.  Since then, the invasive species have been able to use the Mississippi River as a super highway, infesting several of her tributaries, including a handful in Iowa.  

The Iowa Department of Natural Resources has been vigilant in tracking the mob's migration up our rivers. Mark Flammang and Joe Larscheid are two biologists in the field using technology to collect data.

Mark Flammang: This is an electric fishing boat.  We use these to evaluate a lot of different fish species.  They put about 500 volts in the water.

These are actually the electrodes.

Flammang: This would be the positive side of the current, the boat is the negative side of the current so anywhere in between here is where the power is at.

We're starting to see some fish.

Flammang: What it does is it essentially just shocks the fish, it stuns them but it doesn't actually kill them, hurt them or anything.  And then from there we can put them in a tank, measure them and weigh them and get all the data that we need to.

Bighead and silver carp advancements have been kept in check by several dams throughout the state.  These concrete monoliths are generally a dead end to the scaly assailants.

Joe Larscheid: They try to go upstream as far as they can and these flood control reservoirs are a stop cap so they're not getting above those systems.  They are an opportunity to see how many fish are in the system because then they stockpile and they're easy to sample.

Flammang: They're just a funny looking fish. The eye is very low on the head.

But a river without overhead dams is still in danger. This dam at Linn Grove on the Little Sioux River provided a weak spot that the fish were able to exploit during the floods of 2011.  The Missouri River tributary extends into northwest Iowa and connects via Mill Creek to the Lower Garst Spillway.  This gateway to the Iowa great lakes is the lowermost of six glacial lakes that are the backbone of our recreational commerce.  The rallying cry against the expected barrage is one that resonates within the rotunda of Iowa's state capitol.

Senator David Johnson: It would be devastating to the economy -- I think it's urgent that we come up with some way to keep these fish out.

A blue water or spring fed lake is a rare phenomenon.  Only three exist in the world, one of which is West Okoboji Lake in Dickinson County, Iowa.  The notion of Asian carp sneaking into one of Iowa's premier vacation destinations and besieging the natural wonder has the community on edge.

Kim Bogenschutz: It was a surprise to see them there.  I think for the locals it was very much a surprise. For those of us who work with invasive species we knew it was possible.

Kim Bogenschutz, an invasive species expert with the Iowa Department of Natural Resources, has been studying Asian carp in coordination with other states and federal agencies.  Their elusive goal is to control the number of these fish in our connected waterways.

Bogenschutz: Because they are filter feeders they don't bite on bait and they are very difficult to catch. They are net shy.  They jump over nets.  They go through nets.

According to biologists, silver carp only jump during their juvenile stage.  No leaping incidents have been reported in the Iowa great lakes, but none are expected.  Shallow rivers are more apt to promote this behavior.  It is theorized that startled fish simply dive deeper when the space is available.  The behavior tends to cease all together once a silver carp weighs over ten pounds.  

Due to their ravenous appetites, they grow quickly.  But what silver and bighead carp eat is encroaching on Iowa's native game fish.

Bogenschutz: All of our small fish species filter the same plankton out of the water while they are growing.  A lot of them then become fish eaters.  But we have native species, small mouth buffalo, for example, that eat plankton for their entire lives as well so they are in direct competition with the Asian carp.

To top it off, carp are prolific breeders.  It would seem the classic one-two punch is in store for any lake unfortunate enough to be overrun by this nuisance.  Graciously, Mother Nature appears to have granted a reprieve to large bodies of water.

Bogenschutz: Their eggs are, they are buoyant, they float and so they have to remain suspended for a period of time in order for the larval fish to develop.  If they become buried in the sediment they suffocate and die.  And so the large, the long stretches of river is a requirement to keep the eggs floating and viable.

Though it is highly unlikely that Asian carp are capable of breeding in lakes, this doesn't mean populations can't grow to be a problem.  Solutions are being implemented that would keep the fish from expanding their territory.  Mike Hawkins, fisheries management biologist at the Spirit Lake Hatchery, is working on a permanent solution.

Mike Hawkins: What we've proposed is designing and engineering an electric fish barrier at the outlet of the Iowa great lakes that would prevent them from moving upstream.  Water can pass over this type of a barrier and the flows aren't affected.  An electric fish barrier works by sending low voltage electricity into the water.  Fish experience that electrical field, it causes them to turn around and move back downstream.

With a price tag around $700,000 state funds for the barrier fell victim to legislative gridlock.  But a donation by the DNR and local grassroots efforts to raise money for the blockade put a solution within reach.

Bogenschutz: It's not something you just want to put in and hope.  It's got to be done right and we're following the steps as a state to make sure that that happens.  We can control them, we can stop them.  Will we ever get rid of them completely? Probably not but if we keep diligently working, slowing their spread so that there's less of them to get rid of once we do have some better control options -- I think there's hope for the future.


Tags: Asian Carp fish invasive species Iowa lakes pests rivers tourism travel