Plans to deter Asian carp

Exotics...they're here, right here in the Midwest. Thousands of foreign species have been brought to this country both knowingly and unknowingly. Some have been beneficial, while others have been a detriment and have had a profound negative impact on our fragile environment.

One that is really of concern in the Midwest is the Asian carp, both bighead and silver. They are exotic filter feeders, water cleaning machines. They consume plankton and other microscopic organisms, which takes away an extremely important source of food for all sizes of game fish.

As a result, the bighead and silver carp carve out their spot in the system and basically clean out part of the food chain for our game fish. The average size of an adult Asian carp is 30-40 pounds. Since they are capable of eating 5-20 percent of their body weight daily, I think you get the idea of how they can harm the food chain in a body of water.

Currently, they are in the southern Iowa tributaries of the Missouri River, the Big Sioux River, the Mississippi River, the Iowa River south of Iowa City, the Cedar River, the Chariton River below Lake Rathbun and the Des Moines River below Red Rock Reservoir.

The river systems have provided them with the plankton and microscopic organisms for food and the free-flowing waters in which to spawn. Biologists say the flowing water is crucial for egg survival. For a successful spawn to occur, the eggs need to be laid in water that moves fast enough to keep them from sinking to the bottom until they hatch and then the larvae continue to drift for another three days or so.

That means the carp need a river with an unimpeded flow of about 60 miles to pull off a successful spawn. If there is not or the current is too slow, the eggs and larvae are thought to sink to the bottom and die. Thus, the reason for their success in the river systems.

USGS research in the Missouri River shows that the bighead and silver carps can be what are called incremental spawners, which means they spawn a portion of a year's egg production several times over a year. Research shows that they can spawn any time between May and September, but most often in June through early July.

For the larvae that do survive, both the bighead and silver carp grow rapidly. One study showed silver carp reaching up to 12 pounds in a year. Another showed them reaching between 44-66 pounds in 5-8 years. That's under optimal growing conditions. Scientists have also found that when the population explodes, as it has in some of the rivers, growth slows because there are more fish depleting their food source.

While Asian carp are small, they are part of the food chain. Birds and predacious fish will feed on them, but Asian carps grow quickly and soon become too large for native predators. Once that happens, they are at the top of a very short chain and there are very few predators to keep them in check.

One of the areas that people are concerned about is the Great Lakes. The Great Lakes fishery is valued at $7 billion annually. The most probable access to the Great Lakes is through the Chicago Sanitary and Shipping Canal, an artificial connection at the southern basin of Lake Michigan and the Illinois River system. Currently, a permanent electrical barrier is in place to stop the carp movement.

What are some of the other possibilities? What happens if the bighead and silver carp make it into some of our most prized bodies of water? First off, as with other exotics introduced into our country, the impact won't be felt immediately.

It took years before the Asian carp began to be seen as a problem. It simply takes a while, often generations of fish with only a few fish reproducing before a population explosion occurs. For that reason, one long-term solution would be to deny the carp access to their key spawning areas. This plan is being incorporated into several shallow water lakes in the Midwest as a way to control and hopefully to eliminate the common carp with some pretty successful reports.

If the invaded water is a reservoir or lake with no such river tributary, then Asian carp would most likely eventually die out (although this may take more than 20 years).

If there are a limited number of such rivers present in the invaded watershed, it might be possible to deny those rivers to the carp by erecting barriers prohibiting upstream movement to spawn. This strategy might even be used to control or eradicate Asian carp from the Great Lakes, should they become problematic there. Erecting barriers in the extremely large rivers of the central United States where Asian carps are already very abundant is highly unfeasible.

Let's take a look at the current management plan based on the efforts from years of study by the Asian Carp Working Group, which was formed by the U.S. Coast Guard, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, fisheries agencies from the Great Lakes states and provinces, and other organizations, who submitted a Management and Control Plan for Bighead, Black, Grass and Silver carp in the United States to the Aquatic Nuisance Species Task Force.

This 223-page document offers a complete look at the different species of Asian Carp, along with possible ways to stem the tide. The one being used currently is drawing a "line" in the water so to speak, points where the goal is to not let any Asian carp in systems that currently do not have Asian carp populations. Thus, the goal is what biologists call ecological separation: not allowing the carp to move into Asian carp-less waters. Part of the answer is through an intense education program. In other words, getting the words out to the general public. This holds true for all invasive exotic species.

So, what can the general public do? The real answer is using common sense and being an informed and educated general public. First and foremost, do not transport fish from one body of water to another. This holds true for both adult fish and also baitfish. Scientists at USGS stress to all anglers that Young Asian carps could easily be transferred from one body of water to another as baitfish.

In particular, juvenile Silver carp sometimes school with gizzard shad and they are similar in size, shape and color. If you catch your own bait, in addition to being familiar with the bait regulations of your state, it is safest to use the bait only where it was caught and not to transport it to new waters, especially above dams. Many reservoirs in the United States may be vulnerable to invasion by Asian carps, and if they reach high abundance in reservoirs, recreational fishing and boating may be seriously and negatively affected.

If you are interested in learning more about this topic, Chapman recommends these sites: http://www.fws.gov/contaminants/OtherDoc..., http://www.cerc.usgs.gov/ScienceTopics.a... and

http://pubs.usgs.gov/fs/2010/3033/pdf/FS....