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Competition seeks student input on controlling Asian carp

Voracious fish are a threat to North American waters

Nick Mandrak and graduate students (photo by Don Campbell. Photo below courtesy Great Lakes Fishery Commission)

When most of us think of Asian carp we think of YouTube clips of flying fish smacking boaters and water skiers as they pass – although only one species, the silver carp, actually jumps. 

Silver, black, bighead and grass carp all pose a significant ecological threat to the Great Lakes and an existential one to native fish. It’s an issue that’s forcing environmental scientists to come up with ways of reducing the population and preventing the carp from migrating into different watersheds.

The Asian Carp Innovative Solutions Competition hosted by U of T Scarborough on March 5 features student teams pitching their designs and technologies to prevent, control and even eliminate the Asian carp invasion. Writer Don Campbell spoke to U of T Scarborough Professor Nick Mandrak, an expert on aquatic invasive species and the event’s keynote speaker.

Why are Asian carp an important environmental issue?

Asian carp are troublesome because they’re such voracious eaters. Silver carp, for example, can eat a third of their body mass a day and can grow up to a metre long and weigh 50 kilograms (110 pounds). They basically displace native species because they eat all of the available food in a habitat. They also grow so large so quickly that they have no natural predators in North America. In some areas of the United States Asian carp already make up 95 per cent of the total weight of freshwater fishes.  

How did they get introduced into North America?

They were introduced into Arkansas fish farms back in the 1970s. Asian carp were sold to farmers as a means for pest control mostly by the channel catfish industry. Grass carp were used if you had an aquatic weed problem, bigheads were used to control algae and so on. They got into the Mississippi River after a massive flooding where channel catfish farms were built on a flood plain. Since then they have spread north through the Mississippi River, into the Illinois River and are now even in parts of Lake Erie.

Have they made their way into Canadian waters?

You do come across the occasional straggler in Canadian waters, specifically in the Great Lakes. Many of them are around 10 to 15 years old, which is around the time they were banned. They are successfully reproducing in some U.S. waters of Lake Erie but haven’t really infiltrated Canadian waters just yet.

So they aren’t established in Canada but two risk assessments done on three of the four (grass, silver and bighead) carp species show there’s a high probability they will become established in the Great Lakes over the next 20 to 50 years. These assessments also found the impact will be significant, except perhaps for Lake Superior because it’s too cold, unless of course the climate changes, which could likely happen.

Research in my lab is looking at ways in how to control Asian carp or even prevent them from becoming established in the Canadian Great Lakes. In general, not enough is being done. It’s part of the reason why I asked my students to come up with innovative ways to address the problem using not only physical barriers, but biological tactics like hormone disruptors and carbon dioxide bubbles.

What are some ways they can migrate into Canadian waters?

The most obvious route is by spreading into the Great Lakes. But they may also be introduced by anglers using them as illegal fishing bait or by people simply buying them in live fish markets and releasing them. I remember the first Asian carp I saw in Canada was found swimming in a water fountain just south of Queen’s Park. I was working on my PhD and we got a call from a security guard about a funny looking fish that someone had caught in the fountain. Turns out it was a bighead carp that someone had probably bought in a nearby live fish market and released into the fountain, most likely as a prank. It’s the same issue with goldfish. People will just release them into the wild without thinking about the consequences.  

What’s being done to curtail the population and prevent them from migrating even further?

In the U.S. they’ve hired commercial fishing boats to net Asians carp but the problem is that a lot of fish need to be caught. In a couple of hours a boat can catch literally a ton of carp. They tried doing this this two times a day over the course of four weeks using four separate fishing boats and there was no sign that stocks were diminishing. To reduce the population, you would need to catch at least 30 per cent of them to start to see a change. Another issue with fishing for Asian carp is there is hardly a market for them, so the fishing industry has to be subsidized to do it.

Another big challenge is controlling the spread of the fish without disrupting shipping traffic, especially south of Chicago, which accounts for a lot of economic activity. The U.S. Army Corps of Engineers is responsible for maintaining an electrical barrier there meant to prevent the carp from spreading into the Great Lakes, but these barriers are not 100 per cent effective. This is the challenge that my students and students from six other universities and colleges will be rising to at the competition on March 5.