They’re slimy, furry, and cost the U.S. economy more than $100 billion a year. Invasive species have been a costly nuisance to U.S. waterways and landscapes, and now new invaders are taking hold in the Mid-Atlantic. We find out how these species — including one known as “rock snot” — are impacting our region.


  • Lori Williams Executive Director, National Invasive Species Council
  • Jonathan McKnight Biologist, Maryland Department of Natural Resources
  • Mike Dye Wildlife Biologist, Virginia Department of Game and Inland Fisheries


  • 13:08:33

    MR. KOJO NNAMDIFrom WAMU 88.5 at American University in Washington welcome to "The Kojo Nnamdi Show," connecting your neighborhood with the world. They cost the U.S. economy more than $100 billion a year and they're slimy, furry, often ugly and incredibly damaging to the places they call home. Invasive species have been a costly nuisance to U.S. water bodies and landscapes and new invaders take hold in our region each year.

  • 13:09:11

    MR. KOJO NNAMDIJust a few years ago, wild hogs were mainly a problem in the south and west, but hundreds of these incredibly destructive animals have munched their way into our backyards and hunters are on high alert. In our rivers and oceans, cargo ships bring in new species of fish, algae and other aquatic newcomers, threatening the delicate balance of underwater life.

  • 13:09:34

    MR. KOJO NNAMDIBut states are finally cracking down on where and how these vessels can dump the water they bring in from abroad. So who are the newest invaders to our region and what's being done to control them? Joining us in studio is Jonathan McKnight. He is a biologist with the Maryland Department of Natural Resources. Jonathan, good to see you again.

  • 13:09:54

    MR. JONATHAN MCKNIGHTThanks, good to be here.

  • 13:09:55

    NNAMDIThank you for joining us. Also with us in studio is Lori Williams, executive director of the National Invasive Species Council. Lori, thank you for joining us.

  • 13:10:02

    MS. LORI WILLIAMSThanks so much.

  • 13:10:04

    NNAMDIJoining us by telephone from Frederick, Maryland, soon will be Mike Dye. He's a biologist with the Virginia Department of Game and Inland Fisheries. But in the meantime, you can start calling us at 800-433-8850 with your questions or comments. Have you been noticing new species in your backyard? Have you encountered them and do you consider them invasive? Have you noticed new or different species where you have hunted or where you fish? 800-433-8850. Lori, let's start with some of the slimier invaders that we're seeing in our area's water bodies.

  • 13:10:41

    NNAMDIWe're starting to see states really crack down on cargo ships that bring invasive species into the U.S. waters in their ballast tanks. Can you describe how our waters have been affected by these stowaways and what's going on to control them?

  • 13:10:53

    WILLIAMSSure. Ballast water is a major pathway for aquatic invasive species. Of course, it's important for the stability of ships and its water that is transferred all over the world by our cargo ships. And when they come into port, they have traditionally released that water along with the organisms that come along with it. So there's been a concerted effort by the federal government and state government to start addressing this, probably the most important pathway for aquatic species like the zebra and quagga mussels.

  • 13:11:25

    NNAMDIHow are they addressing them?

  • 13:11:28

    WILLIAMSRight now, the regulation that's in place is requiring, the federal regulation, is the ballast water exchange so that you have to exchange your ballast water way far out of port so hopefully most of the organisms then are released far out from sea and don't establish in the coastal areas. The federal government is looking at strengthening that standard. A number of states now have moved to put their own standards in place. It's a complicated technological issue, but it's one of the most important things we could do to stop invasive species.

  • 13:11:58

    NNAMDIJonathan McKnight, ballast water has recently brought in a new kind of shrimp to the Chesapeake Bay. Tell us about the oriental shrimp invasion and the threat it poses?

  • 13:12:08

    MCKNIGHTWell, we really don't know much about the oriental shrimp. We're, in fact, tracking it now trying to find out where it occurs in Chesapeake Bay estuaries that's going on in Maryland and Virginia. The problem is that this shrimp is very closely related to the native grass shrimp, which is a very basic part of the Chesapeake Bay food web. And if this oriental version of the grass shrimp is able to displace some amount of our native population, that's a big a deal because a lot of organisms in the Chesapeake Bay are counting on that shrimp population being there at a certain time of the year and acting in a certain way.

  • 13:12:53

    MCKNIGHTSo there's a fair amount of concern. One of the problems when you get one of these new species in is that it's very difficult to predict in advance what it's going to do. So with this shrimp, it's an experiment we're unfortunately running in the wild.

  • 13:13:06

    NNAMDIHow do these shrimp differ in appearance to grass shrimp?

  • 13:13:11

    MCKNIGHTThey're very similar. It's takes an expert to tell them apart and that's why the folks who are currently doing the work, trying to find out the degree of that invasion are university and Smithsonian-based experts on shrimp.

  • 13:13:27

    NNAMDIWhat other kinds of invasive species have infected our waters from these ballast water pumps and what kind of damage are they doing?

  • 13:13:34

    MCKNIGHTWell, the poster child for ballast water is the zebra mussel, which is a little mussel similar to what people think of as a mussel they'd find at the sea shore, except that it's a fresh-water creature. And these were released into the Great Lakes not that long ago in the early 1980s and since then, they've spread throughout different part of North America. It's actually the zebra mussel and its little cousin, the quagga mussel.

  • 13:14:01

    MCKNIGHTThey're a huge problem because they get into all sorts of water systems and they basically will attach themselves to any hard surface. So they're costing millions of dollars to states that have things like water-dependent power plants. They will get into marine engines and actually gum the works up.

  • 13:14:22

    NNAMDIWe're talking with Jonathan McKnight. He's a biologist with the Maryland Department of Natural Resources and Lori Williams, executive director of the National Invasive Species Council. Joining us now by telephone from Fredericksburg is Mike Dye. He's a biologist with the Virginia Department of Game and Inland Fisheries. Mike Dye, thank you for joining us.

  • 13:14:41

    MR. MIKE DYEThank you for having me.

  • 13:14:42

    NNAMDIMike, we're talking about invasive species that have been infecting our water. Any concerns along that line, Chinese mitten crabs?

  • 13:14:51

    DYEWell, as far as that goes, I'm not as familiar with the aquatic side. I deal more with the terrestrial.

  • 13:14:57

    NNAMDIOh, well, we'll get to that in a second so let me ask Jonathan about these Chinese mitten crabs. Are you familiar with those?

  • 13:15:03

    MCKNIGHTI'm familiar with them. We've had a number of them show up in the port of Baltimore or outside of the port of Baltimore. It's of great concern because when these affected rivers on the West coast, they found huge numbers of these things. We don't know that we have a self-sustaining population of these in the Chesapeake Bay. In fact, we think now we probably don't. It looks, however, like there may be a population in the Hudson River. My personal opinion is that the crabs that we found in Baltimore have fallen off of ships, mostly from Baltic ports, but it's one we're monitoring closely.

  • 13:15:38

    MCKNIGHTIf they become established in fresh water systems in the Hudson, it's going to be that much harder to keep them out of the Chesapeake.

  • 13:15:47

    NNAMDILori, I was about to say, what should we do if we see or catch any of these creatures in the Chesapeake Bay?

  • 13:15:50

    WILLIAMSI think it's of great concern and the people -- people really have a lot of power on this issue because a lot of the early identifications are made by citizens. The scientists can't be everywhere. The government officials can't be everywhere. And increasingly, states like Maryland have their own invasive species councils. They have numbers that you can call to report things. You can call the state officials. That's probably the best place to start is your state government, your state officials for new species. If it's a new species in the country, they will then call the federal officials.

  • 13:16:24

    WILLIAMSBut early detection and rapid response is one of our best weapons against these species. If you can find them early enough before they really become established, then you can eradicate them and then you don't have this continued cost for control over years and years.

  • 13:16:39

    NNAMDIWe're talking about invasive species and inviting your calls at 800-433-8850. Have you noticed new or different species where you live, where you hunt or where you fish? 800-433-8850. Do you think controlling or eliminating these species from our waters is possible? Again, the number 800-433-8850. Mike Dye, let's talk a little bit now about wild hogs. There's been an alarming increase in these incredibly destructive animals in the past three decades throughout the country and they're now knocking on our door. What are you seeing? What are we seeing in Virginia?

  • 13:17:19

    DYEWell, the population here in Virginia is absolutely increasing. We're noticing fairly large increases at least over the last ten years within our area. I guess the closest to your listening area is a population in Southern Culpeper County. The population there is fairly robust. We have probably three to four hundred animals in that population. But luckily, it's pretty well -- it seems to rely on one location. It's not spread out over a real wide area and we're hoping to keep it that way.

  • 13:17:49

    NNAMDIHow destructive are these animals and what kind of damage do they do?

  • 13:17:52

    DYEWell, they can be very destructive. Of course, you know, you think of eating, you know, someone eating like a pig. You know, basically they eat anything and everything. They eat a lot of the native wildlife, for example, a ground-nesting songbird nest or if you think of a wild turkey or a quail nest. If they come across that, they're going to eat it.

  • 13:18:14

    DYEThey also do a lot of ecological damage from the standpoint of damage along creek banks. They're very tied to water because they do not have the ability to thermo-regulate so they need to use the water and the mud in order to, you know, cool themselves down. So they can do a lot of damage, you know, from a water quality standpoint, but also they can damage a lot of fragile eco-systems along the raperian edges that can lead to increased runoff, increased, you know, levels of bacteria in the water. But they can really damage those fragile plants on those raperian areas.

  • 13:18:57

    NNAMDIWhy are they spreading in Virginia?

  • 13:19:01

    DYEWell, unfortunately, the biggest cause of spread for wild pigs is people hunting them. It's a very popular pastime especially in the southeast and hunters are learning that they're fun to hunt because they are -- they're very intelligent, very wary of people so they are kind of fun to hunt. And hunters are, a lot of times, relocating these animals to different locations. And we're hoping to stem the tide on that and try to prevent people from moving them around. But a lot of people -- with feral pigs, it's something that unless you have had to deal with them, you don't realize how bad they can be, how destructive they can be.

  • 13:19:40

    NNAMDILori, these animals are now in at least 39 states, including Pennsylvania and West Virginia. What is the National Invasive Species Council doing to try to prevent their spread?

  • 13:19:51

    WILLIAMSThis is a very difficult species, just as you've discussed. One of things that we're doing is that we're encouraging the states to work together. They can learn from each other best management practices. And what's happened in Texas, they've a lot of experience with these species in different states. And we are having a meeting here in a couple weeks, the National Invasive Species Awareness Week. And the states will be getting together and sharing best management practices, sharing how they control different species, sharing how they can work better together and find better funding sources. So this is really important on a wide spread species like this.

  • 13:20:26

    NNAMDIMike, how do these wild pigs differ in size or demeanor from domestic pigs?

  • 13:20:31

    DYEIn size, they tend to be a little bit smaller. You have to remember they're living out in the wild. They're finding their own food sources. They don't have a person supplying, you know, constant supply of corn to them. So they tend to be a little bit smaller. They can be a little bit more aggressive. You know, once a pigs been out in the wild for a couple generations, you know, they become -- they start to become more like their ancestral European wild boars.

  • 13:20:57

    DYEAnd they still have all the same genetics. They tend to start showing a little bit more of a wild nature. They will grow tusks. They will grow longer hair and, you know, start to redevelop a more wild appearance.

  • 13:21:11

    NNAMDIOn -- go ahead.

  • 13:21:12

    DYEBut as far as demeanor, they're not extremely dangerous. They can in some instances become a little more aggressive than a standard domestic pig. But most of the time they're pretty afraid of humans.

  • 13:21:23

    NNAMDIMike Dye is a biologist with the Virginia Department of Game and Inland Fisheries. He joins us by telephone. In our studio is Lori Williams, executive director of the Invasive Species Council and Jonathan McKnight, a biologist with the Maryland Department of Natural Resources. We go to James in Hurlock, Md. James, you're on the air. Go ahead, please.

  • 13:21:43

    JAMESYes, good afternoon, Kojo. Thank you very much for the opportunity. I'd like to thank the Department of Natural Resources for the successful -- I hope eradication of the mute swans in the Chesapeake Bay water shed. I know that they've been a problem for some years and I'd like to ask the DNR if they've a got a handle on them now and are they gone? Thank you.

  • 13:22:03

    NNAMDIJonathan McKnight?

  • 13:22:05

    MCKNIGHTThanks, James. I appreciate your pat on the back. Yeah, the mute swans, Kojo, were a population of escaped feral swans that at one point had reached about 4,000 in the Chesapeake Bay. A number of years ago, we became increasingly concerned about the effect they were having on native water fowl. And after a long court battle, we ended up with a very aggressive program to reduce those numbers.

  • 13:22:31

    MCKNIGHTAs I said, we had about 4,000. We've been working very hard on this with our biologists and our trained teams in the field. Currently, the Chesapeake Bay population is just below 200 swans. Obviously, the thinner that population is, the harder they are to get to. But that population is down to less than 5 percent of its original size. Frankly, it's been a very successful program and I appreciate James noticing. They're not gone from the Chesapeake, but they're a much reduced hazard.

  • 13:23:00

    NNAMDIThank you very much for your call, James. We move on to Matt in Washington, D.C. Matt, you're on the air. Go ahead, please.

  • 13:23:09

    MATTHey, good afternoon, thank you for having me on.

  • 13:23:11

    NNAMDIYou're welcome.

  • 13:23:13

    MATTMy question is really what constitutes a -- you know, specifically to the German brown trout, which I know that Maryland DNR and I'm sure the Virginia DNR and I know Pennsylvania's DNR, stocks. And, you know, those initially were brought over -- and correct me if I'm wrong, but they were initially brought over during the German times to stock their more hardy fish than the natural brook trout in the area. And, you know, what constitutes a non-native species or invasive species and when do we start supporting it and, you know, is there talk?

  • 13:23:48

    MATTI mean, to get rid of them. You know, I mean, this is obviously something that my tax dollars go to support. I support -- I fish them, you know, myself, but, you know, is there a time frame that we now say, okay, this is a native species, been around for 50 years?

  • 13:24:03

    NNAMDILori Williams?

  • 13:24:05

    WILLIAMSYes. Just to clarify the definition of an invasive species at least under our executive order, it's really important to distinguish between just non-native species, which we have many of. In fact, many of our crops are non-native, many of the species that we depend on are non-native and invasive, which are both non-native and considered harmful to the economy, the environment or sometimes even human health.

  • 13:24:28

    WILLIAMSSo that is -- sometimes a difficult determination, but it's got to be both. And very few species are listed as federally invasive, just a few noxious weeds and a few species of animals. The states often make that decision. So I'll turn it over to the states. But not all non-native species, by any means, are considered invasive. I just wanted to make that point.

  • 13:24:49


  • 13:24:50

    MCKNIGHTI think Matt makes a really good point. States, agencies, people in general, actually, have a long history of being the ones who are purposely spreading many of these species around. And certainly the Fish and Game Departments of the various states and the Federal Department of the Interior have been very guilty of haphazardly spreading biological material around. The brown trout, for many years, was one of those species everyone pointed to and said, well, here's a great species. It's not native, but everybody likes to catch it. It doesn't do any harm.

  • 13:25:20

    MCKNIGHTMore and more, we're seeing evidence that the brown trout, in fact, does behave, in some circumstances, as a invasive species. It can drive ecological pressure on natives species and, I think, the question of where is it appropriate to stock this and when is the time to stop is an important issue Matt's tapped into. It's a conversation that's ongoing in every department of natural resources certainly, including Maryland.

  • 13:25:47

    NNAMDIMatt, thanks for your contribution to that conversation. Back to you, Mike Dye, and wild pigs. What kind of health threat do wild pigs pose for humans and other animals?

  • 13:25:57

    DYEWell, they do pose quite a few threats. They carry -- they are a reservoir of several diseases, such as Brucellosis, Leptospirosis, Salmonella, you know, Pseudorabies and, you know, several other diseases. A lot of these diseases are, you know, especially dangerous in the transmission to livestock. That's one of our main concerns. We've actually been working quite closely with the U.S. Department of Agriculture through their wildlife services unit trying to capture some of these hogs and take some disease samples from them, you know, that way we can test these to make sure they're not spreading diseases around to, you know, local wildlife populations or local livestock.

  • 13:26:40

    NNAMDIIs it open season on these pigs for hunters?

  • 13:26:43

    DYEAbsolutely. They are declared a nuisance species here in Virginia and they can be hunted any day of the week except Sunday. And you can also hunt them at night with the aid of a spotlight and you can also use bait to hunt them with.

  • 13:26:59

    NNAMDICan you eat them if you hunt them?

  • 13:27:02


  • 13:27:03

    NNAMDIHave you tasted wild pig yourself, Mike?

  • 13:27:06

    DYEYes, I have. They're very delicious. They have a little bit stronger flavor than domestic pork does. So, you know, some people don't like it as much. I tend to favor it a little bit more over domestic pork myself.

  • 13:27:18

    NNAMDISo people can hunt them and they can eat them, too?

  • 13:27:20


  • 13:27:22

    NNAMDIMike Dye, thank you so much for joining us. Mike Dye is a biologist with the Virginia Department and Game and Inland Fisheries. Still with us is Jonathan McKnight, biologist with the Maryland Department of Natural Resources and Lori Williams, executive director of the Invasive Species Council. If you have called, stay on the line. We're going to take a short break. After all, this is our winter membership campaign. But after that, we'll come back to this conversation about Invasive Species. So you can still call 800-433-8850 or you can go to our website and join the conversation, ask a question or make a comment there, that's I'm Kojo Nnamdi.

  • 13:37:16

    NNAMDIWelcome back to our conversation on Invasive Species with Lori Williams, executive director of the Invasive Species Council and Jonathan McKnight. He's a biologist with the Maryland Department of Natural Resources. I'm going to step back and allow the callers and e-mailers to take over because you've been waiting for a while. Thank you for doing that. So first, here is Clyde in Berryville, Va. Hi, Clyde.

  • 13:37:41

    CLYDEHi, Kojo. Thank you for taking my call.

  • 13:37:44

    NNAMDIYou're welcome.

  • 13:37:45

    CLYDEI live in the Northern Shenandoah Valley and I'm told we have an invasive species called stink bugs and I'm experiencing an invasion of them. Is there anything that can be done about them?

  • 13:37:59

    NNAMDIClyde, I'm going to put you on hold for a second so you can continue to listen even as we hear from Nigel in Shepherdstown, W. Va. Nigel, your turn.

  • 13:38:10

    NIGELYeah, I -- thank you, Kojo. We do have an invasion of stink bugs. The county this year, Jefferson County, was taken over by stink bugs. The soybean crops were decimated completely. There was a lecture at the National Conservation Training Center last week, but I was in England so I missed it. So I would love to know what your panel thinks about it.

  • 13:38:40

    NNAMDIWell, first you, Lori.

  • 13:38:42

    WILLIAMSWell, this is a little bit embarrassing because I have stink bugs in my neighborhood and I'm one of the few households that have not suffered from them. And that, of course, is the purview of U.S.D.A. some of these flying invasions.

  • 13:38:57

    NNAMDIIs there a sign outside your house saying, executive director of the Invasive Species Council?

  • 13:39:01

    WILLIAMSThere must be.

  • 13:39:01

    NNAMDICan the stink bugs read?

  • 13:39:03

    WILLIAMSExactly. But I'm not an expert on the stink bug. I'm...

  • 13:39:06

    NNAMDIHow about you, Jonathan?

  • 13:39:08

    MCKNIGHTThis is the brown marmorated stink bug, which is an exotic stink bug. We actually have a lot of native stink bugs which behave much more nicely than this one does. This one tends to come into people's houses. Like many of these others, it's an experiment that's being fought out in the wild. First, it was a problem in suburban neighborhoods. The last couple of years, it's been an increasingly major agricultural pest.

  • 13:39:32

    MCKNIGHTWe're waiting to see what it will do as far as natural ecosystems and places out in the wilderness. I don’t know of any way to stop this one. And it really illustrates the situation with invasive species where often once they're introduced, there's nothing that you can do about it, practically, which is why our focus really is focused on preventing these things from getting in in the first place.

  • 13:39:59

    NNAMDILori Williams?

  • 13:40:00

    WILLIAMSAnd that really is a huge emphasis both to the states and the federal government, and prevention sounds very difficult, but there are known pathways that these species get in, trade, travel and tourism, the three Ts. And their best management practice is that we can start taking, and have started taking in some cases, that can limit the introduction of these species. So we have fewer stink bugs in the future.

  • 13:40:22

    NNAMDINigel, thank you very much for your call. Clyde, does that work for you also?

  • 13:40:27

    CLYDEYes, you're welcome. Thank you.

  • 13:40:28

    NNAMDIThank you also for your call, Clyde. You too could call us, 800-433-8850. Earlier in the conversation we were talking about invasive species infecting our water from ballast water dumps. I think that is what Gary in Alexandria, Va. would like to ask about. Gary, you're in the air. Go ahead, please.

  • 13:40:47

    GARYYes, good afternoon. I was wondering if there are any efforts being made to stop the invasive species like the fish and mussels that get in these tanks at the source, electrifying the water in the tanks or doing something chemically. It seems like dumping the water further out to sea is just gonna shift the problem elsewhere.

  • 13:41:10

    WILLIAMSYou're very correct in that my understanding of the ballast water issue is that ballast water exchange is not the best method. What -- what the Coast Guard is doing is trying to develop a standard of what is safe and what do these -- the technologies need to meet to make sure very few species are introduced. And there's a whole range of entrepreneurs out there that are experimenting with everything from chlorine to electrifying the water to all kinds of strategies.

  • 13:41:39

    WILLIAMSThe difficulty has been making those strategies not so much that they can kill the invasive species, they can kill the species, but are they gonna work in the very complicated environment on board a ship. And it's those two things that need to come together. But I -- I believe that given the level of activity now that we're gonna start seeing progress on this issue. I'm very hopeful in the next few years.

  • 13:42:00

    NNAMDIJonathan McKnight?

  • 13:42:02

    MCKNIGHTYeah. It's interesting. There's actually an experimental ship in Baltimore Harbor where some terrific scientists from the University of Maryland are testing out some of those technologies. It's fascinating to watch.

  • 13:42:12

    NNAMDIBecause I was gonna ask, do U.S. vessels take an invasive species to other regions of the world also?

  • 13:42:19


  • 13:42:19

    NNAMDIIt's a problem on both sides. And so that's why I guess this kind of experiment is important.

  • 13:42:23

    MCKNIGHTThat's correct.

  • 13:42:24

    NNAMDIBecause it can teach people all over the world. Gary, thank you very much for your call. We move on to Erik in Alexandria, Va. Erik, you're on the air. Go ahead, please.

  • 13:42:36

    ERIKHi, good afternoon. Thank you for accepting my call.

  • 13:42:39

    NNAMDIYou're welcome.

  • 13:42:39

    ERIKMy question is, I'm a contract police officer for WASA, Department of Water and Sewer Authority for Washington D.C.

  • 13:42:47


  • 13:42:48

    ERIKAnd we have 30 hits that we hit, and most of the hits are on water, and the question I have is about these, I think, Canadian geese, the big brown multi-colored birds -- is that Canadian geese?

  • 13:43:01

    NNAMDIYes, indeed.

  • 13:43:03

    ERIKOkay. They are, oh, my goodness, they wreak havoc.

  • 13:43:06

    NNAMDIThey can be very aggressive, too.

  • 13:43:07

    ERIKIs that -- is that -- oh, yes, very aggressive. Is that considered an invasive bird?

  • 13:43:13

    NNAMDIJonathan McKnight.

  • 13:43:15

    MCKNIGHTActually, it is. There are two different kinds of Canada geese in the world, one is our migratory geese that go up to northern Canada and hang out there in the warm weather, and then only come back and they're in the Chesapeake Bay region in the winter time. And the other is this population of resident Canada geese which are giving you such a hard time around the waterways. And I think if you talked to golf course owners and park managers, you'd find out they're a big problem wherever you go.

  • 13:43:43

    MCKNIGHTWe've got right now about 80,000 of these resident Canada geese in our -- in an area around Maryland and Washington. The number ought to be much lower, and it's a terrific problem. What a lot of people don't realize is that these are not just geese that decided to stop migrating. These are actually the descendents of pet geese that were released that were part of flocks that were kept for live decoys when it was made illegal to hunt over live decoys, people just released their geese.

  • 13:44:16

    MCKNIGHTThey're a different subspecies from our migratory geese, and they're really just a feral goose population that are out there multiplying and growing and growing. Like a lot of other invasive species, they found terrific habitat in the suburbs and in the interstitial areas of where we're living.

  • 13:44:37

    ERIKSo what is being done to try to get that together?

  • 13:44:41

    MCKNIGHTThe basic mechanisms we use are that if people are having a tremendous problem with them, we'll give them technical support in what they can do to control them, and we'll give them permits so that they can control them. Some people are trying to drive them off, other people are trying to actually round them up and lethally control them, to kill them to get rid of them.

  • 13:45:03

    NNAMDIOkay. Thank you very much for your call, Erik. We got an e-mail from Zack in Washington. "What do panelists think of the use of biological controls, especially in the case of invasive plants such as kudzu, mile-a-minute vine and others? I think they can be very effective. But at the same time, I am very cautious about releasing more non-natives."

  • 13:45:24

    WILLIAMSThat's an excellent question, and this is another tool that can be used on invasive species, especially wide spread species. And the key is to do the scientific research to make sure you find a biological control that only eats that invasive species, that doesn't eat the native species, or doesn't prey on -- or doesn't damage the native species. So there's a whole series of scientific experiments you need to do to make sure you're only affecting the target species. And then it really can be very effective.

  • 13:45:55

    NNAMDIAgain, we're taking your calls at 800-433-8850. Have you noticed new or different species where you hunted or fished, or would out eat wild hog, Asian carp, or even a snakehead fish if you could? 800-433-8850. I bring up the snakehead fish because one of our regular guests on the show, Candy Thompson of the Baltimore Sun, just wrote a piece about the northern snakehead fish, which have exploded in number in the Potomac in recent years. How has it gotten so bad, and do you worry about them getting into the Chesapeake Bay?

  • 13:46:29

    MCKNIGHTWell, unfortunately, Kojo, they've already apparently been able to get very close to the Chesapeake Bay and perhaps even around the corner of the Chesapeake Bay into some other rivers. I think there's a real danger that some misguided fisherman will transport them around as well. Uh, it's another example of a species that's found a habitat that it can adapt very well to, once it was introduced there.

  • 13:46:54

    MCKNIGHTThere are tens of thousands of them here at the -- in the nation's river, in the title part of the Potomac River. And very little chance that we can do much with them. It's...

  • 13:47:05

    NNAMDIWe've got a lot of calls and e-mail about snakehead fish, so let me try to get through a couple of them quickly. Here's Erik in Arlington, Va. Erik, you're on the air. Go ahead, please.

  • 13:47:15

    ERIKHow you doing? Love the show, Kojo. I just wanted to say that I read a couple years ago, an article about -- in the Washington Post, about snakeheads and everything and how their introduction into the waters was affecting it. Because years ago I used to go fishing with my father and we'd always catch bass or something, and just encounter a couple snakes here and there, but now it seems that you -- like you see very rare people going into the river because the only thing they come up with snakeheads.

  • 13:47:42

    ERIKAnd is there any real thing that they're -- any real measure that is taking to -- to try to prevent it to spread other rivers and stuff?

  • 13:47:51

    NNAMDIErik, hold for a second and let me get to Jonathan in Fairfax, Va. before I ask our panelist to answer those questions. Jonathan, you are now on the air. Go ahead, please.

  • 13:48:02

    JONATHANThank you, Kojo for taking my call. I have a comment and a question. When I hear about a lot of the early identifications about non-native species, the news tends to portray them in worst case scenarios, and I think the snakeheads is a great example. You know, ecosystem collapse, native fish species collapse, and it seems like some of the articles I've read about snakeheads haven't really found that they've had a huge detrimental impact on the ecosystems, perhaps even they're a tasty game fish.

  • 13:48:29

    JONATHANAnd I kind of worry that when these things fall out of the news that people tend to think that scientists are over exaggerating the fears and I didn't know if you guys wanted to comment on some of the complexities of, you know, the early stages of development when you're looking at invasive species, especially snakehead versus later and how, you know, you can portray these complexities to the public.

  • 13:48:47

    NNAMDIFirst you, Lori Williams.

  • 13:48:50

    WILLIAMSI think that's a very good point, and what we're really talking about is the risk to the environment. Early on we really don't know what impact they're gonna have, but the question is, if we know they've been a problem somewhere else, or we know that they're gonna adapt well to the conditions, we have to state the risk. And the risk is ecological collapse. That doesn't mean it's gonna happen in all cases and there aren't things that we can do.

  • 13:49:15

    WILLIAMSI guess what our preference is, is prevention is most cases unless there's a real reason to introduce a new species into -- into a river because what you don't know can hurt you, and that's our point. But I think we have to be very careful that you don't know how these species are exactly gonna interact with the environment until you do as we've talked about, an uncontrolled experiment. It's just those uncontrolled experiments can be very costly.

  • 13:49:40


  • 13:49:41

    MCKNIGHTWell, to Jonathan's point about a worst case scenario, I think that the snakeheads certainly captured the popular imagination. I mean, movies have been made about the snake fish. It was pretty dramatic as far as the way the press treated that one. It was sort of uniquely ugly and nasty. As far as it being a tasty game fish, that is absolutely the case, and I encourage everyone to go catch a snakehead right away, take it home and cook it and eat it. Make sure you kill it first.

  • 13:50:11

    MCKNIGHTBut that's one of the -- our best hope is that we can get everybody to eat those things. Going to Erik's point about the snakeheads in the Potomac River, the snakeheads are not actually driving out other fish, and he made mention of bass and snakes and things like that. There are still a tremendous bass fishery in the Potomac River. What people don't often realize is that the bass and the catfish and many of the other fish that people are worried about protecting in the Potomac River are in fact non-native species themselves.

  • 13:50:41

    MCKNIGHTSo in the Potomac River because it's such an urban river, we've got just a mishmash of species from other places that are kind of going to fight it out over the next 10, 20, 50, 100 years, and we'll have to wait and see what the ecological effects are, and who the winners and losers will be in that game. What we know from experience is that the winners are very rarely the native species.

  • 13:51:05

    NNAMDIAnd finally there's this from Dan. "I enjoy spear fishing and wanted to know if targeting the snakehead fish by spear would be an effective method of controlling the Potomac? A trained spear fisher can target a particular fish species and especially in an environment where they are not used to seeing divers, can rack up a good number of kills in a short time." Jonathan?

  • 13:51:27

    MCKNIGHTDan, go get them, buddy.

  • 13:51:29

    NNAMDIAnd this Jonathan, thank you so much for calling. And to you, Erik, thank you for calling also. Wanted to get to another issue, speaking of slimy stowaways. Another more disgusting organism is hitching a ride into Maryland waters, and its presence is literally changing the way fisherman dress. Tell us about the didymo, also known as rock snot.

  • 13:51:53

    MCKNIGHTYeah. This is sort of a tragic story. This is a fairly horrible creature. It's a unicellular algae, fairly innocuous on its own, native in fact to parts of the northwestern United States. But what it's been able to do is move itself around the planet, clinging to the shoes of fisherman. It's been a problem in New Zealand, it's in Scotland, it's in many of the major fly fishing rivers, and in fact its occurrence in famous rivers is what first give scientists the idea that uh-oh, this is traveling fly fishermen who may actually be the vector for the spread of this critter.

  • 13:52:34

    MCKNIGHTIt first showed up in Maryland two years ago in one of our rivers known for its fly fishing opportunities, the Gunpowder Falls. And we've been working really hard to contain it there. One of the things that's come out of that is that some fly fisherman favor a wader with a felt sole which is -- has remarkable traction on slimy rocks, and they'll use it to get a good grip on the bottom.

  • 13:53:01

    MCKNIGHTUnfortunately, research has shown that this felt sole is an almost ideal environment for sustaining and transporting this unicellular algae around. So like many other states, Maryland is getting ready to make it illegal to use that sole in fishing, and...

  • 13:53:17

    NNAMDIAnd that's -- that's my final question for you, Lori Williams. Those felt-soled waders as Jonathan pointed out are likely to be banned in Maryland after March, and they're already banned in Alaska, Vermont and New Zealand. Is banning these waders enough, or do we think it's being transferred by other means as well?

  • 13:53:32

    WILLIAMSIt could be transferred by other means as well. One of the encouraging things though on this story is that that fly fishing associations are getting involved. Some of the tackle stores are getting involved. This is a pathway that can be addressed. Not just by banning certain equipment which might be important, but also through public education. These -- the fisherman don't want to see this spread around, and we can make them allies in our fight against this invasive species.

  • 13:53:59

    NNAMDILori Williams is executive director of the Invasive Species Council. Thank you so much for joining us. Jonathan McKnight is a biologist with the Maryland Department of Natural Resources. Good to see you again. Thank you for dropping by.

  • 13:54:09

    MCKNIGHTThank you.

  • 13:54:10

    NNAMDIAnd thank you all for listening. I'm Kojo Nnamdi.

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