In some parts of the world Carp are a coveted part of the culture, while in others, they are despised. Many species of Carp are a huge part of aquaculture, medicine, and food in most parts of Asia. Carp are primarily filter feeders but also eat vegetation in aquatic environments. In the 1970's, aquatic managers decided to begin using Carp to rid their ponds of vegetation. The carp were an instrumental aspect of the aquaculture economy and sewage treatment plants in the southern United States. Years after they began being stocked in the south, record rainfall fell and the escape of an invasive species began.
Silver, Bighead, and Grass Carp gained access to tributaries of the Mississippi when the ponds they were contained in ran over their banks. In the early 90's, these fish made their way out of a contained environment and began their spread. Due to their fast growth and large adult size, the fish have very few predators.
The Bighead and Silver Carp are also prolific reproducers. With these characteristics combined, they have quickly gained the label as one of the most invasive species in North America. Silver carp can produce nearly 300,000 eggs per spawn. In ideal conditions, these fish can spawn three times per year, producing just under one million eggs per fish each year. These numbers far out reach reproduction rates of native species of fish.
These fish aren't eating what native species eat, but the plankton the Carp filter out of the water is taking food away from many of the bait fish native fish feed on. Their incredible reproduction allows them to far outnumber other species and they quickly begin to outcompete others for food. Soon after their escape from aquaculture ponds and sewage plants, they began to hinder the growth of highly sought after game fish in areas of the Mississippi river. Just as any species does, they began to expand their range in search of food. They spread into tributaries and began to come north into the mid-west.
A few weeks ago, I traveled to the Illinois River and spoke with a large river ecologist who studies invasive species on an 80 mile stretch of the river. This 80 mile stretch is often referred to as the epicenter of the Asian Carp invasion. The first Asian Silver Carp was found in the 90's. In the time since then, fisherman have gone from catching very few to the point where few spend time fishing the river. The Carp are not only depleting sport fish such as Bass, Walleye, and Catfish, but also find their way into the fisherman's boats. The Silver Carp are a nervous species and the noise and vibration of boat motors and paddles often makes them jump out of the water. These fish can rocket some 5-8 foot into the air. They will not only land in boats splattering slime and blood, but can also hit boaters creating a high risk for injury or even death. The fish can grow to sizes over 30 pounds. Imagine a 30 pound fish coming out of the water and hitting a boater who is traveling 20 miles per hour down the river! There have been reports of broken jaws and concussions from boaters and jet-skiers all throughout the range of the Asian Silver Carp. A census in 2007 found 7,000 Asian Carp per square mile of this portion of the Illinois River. The sizes and numbers of native fish in this area have shrunk since the Asian Carp first arrived.
We only spent an hour of filming Carp and had more than enough footage to produce a 30 minute television episode regarding the management of Asian Carp. The number of fish in the air at once was incredible! One of the boats was equipped with a generator and shocking electrodes. Good numbers of fish were in the air nearly constantly, but when the electrodes were turned on, the numbers were astounding! It was a battle to dodge the fish and prevent being slimed and to keep the cameras safe. Hundreds of fish found their way into the bottom of the boat, but luckily, only a few used us as a target.
Many fear the Asian Carp species will continue to spread north and find their way into the Great Lakes. If they were to make their way there, it would be devastating to the vast fishing industry that calls the Great Lakes home. Electronic barriers have been utilized in canals leading to Lake Michigan in Chicago, but recently a Bighead Carp was found past the barrier. Many opinions on management methods have been discussed and some are being tried, but it is yet to be determined if they will work.
Asian Carp are found all throughout the world, and in every location other than the United States, they are over fished. Many people here in the states want nothing to do with eating Carp due to their boney structure. In other countries they are considered a delicacy and can easily be found at fish markets and grocery stores. They are commercially fished and this allows these countries to keep their numbers in check. Since very few people in the United States are interested in eating the fish, there has been very little market for them until recently. The United States has signed a multi-million pound deal with Asia to export commercially caught Asian Carp. An average commercial fishing outfit can pull around 10,000 pounds of fish a day. There are hopes that the deal is a success and the partnership will continue. If all goes well, this will hopefully keep the invasive Asian Carp from further spreading and depleting the native species in waters throughout the United States.
Up until recently, the Asian Carp have only been affecting the river communities along the waters they exist. But with the quick spread of their range, they could begin to affect many others if they were to gain access to the waters of the Great Lakes. Much is being done to prevent this, but for now everything is trial and error. Let's hope the commercial deal will allow us to prevent the further spread of the invasive Bighead, Silver, and Grass Carp.