The round goby is a relatively small fish, but they are causing big problems in the Great Lakes, including Lake Erie and some of its tributaries in Pennsylvania. Sara Stahlman is extension leader for Pennsylvania Sea Grant, an organization focused on conservation. She’s co-organizing an event on December 6 with the PA Governor’s Invasive Species Council to get anglers in the northwestern part of the state to help stop the spread of the invasive fish into inland waterways. Stahlman spoke with The Allegheny Front’s Kara Holsopple about it.
LISTEN to the interview
Kara Holsopple: Tell me a little bit about the species. What does it look like?
Sara Stahlman: The round goby is pretty small. They can get up to about five inches, but they’re this bottom-dwelling fish. They have little like frog-like, raised eyes. They kind of look like a sculpin. That’s another species that they’re a look-alike of or a darter. But they have a suction cup-shaped fin that actually allows them to anchor to the bottom of rocks. They’re kind of cute, but it’s pretty deceiving because they can cause a lot of problems.
Kara Holsopple: How did the round goby get here to Pennsylvania?
Sara Stahlman: The round goby is actually native to Eurasia in the Caspian, Black and Azov Sea region. They’re actually from the same area as the zebra mussel. They coexist with the zebra mussel and actually feed on it.
Both zebra mussels and round goby were initially introduced into the United States through ballast water. As ships are moving cargo back and forth between these areas in Eurasia and the Great Lakes, they have cargo holds that are empty. They bring in that ballast water along with the organisms that are in the water at that time. They then come fill up with whatever they’re picking up at that port, and they dump out the ballast. They don’t need that anymore to stabilize the ship. It releases species like round goby and zebra mussels.
Round goby are very good at adapting. They were introduced in the 1990s and have spread throughout the Great Lakes region. That’s how they were able to get into Pennsylvania through Lake Erie. Then, in some of our inland areas, they’ve been introduced because the round goby is often now used as bait or mixed in with bait.
Kara Holsopple: Why round goby an issue in Lake Erie and tributaries like French Creek? What kind of problems do they cause?
Sara Stahlman: Even though they’re small, they are very aggressive. They can actually outcompete native fish for food and habitat. They’ll feed on the eggs of native sport fish like bass. They aggressively defend nesting sites, and they can actually feed in complete darkness. So they kind of have this competitive advantage over other fish. They’re actually defending nest sites, so that allows their reproductive success because their offspring are able to survive. They’re voracious feeders, so they’re consuming a lot of the resources that our native fish need. They have a pretty heavy ecological impact. They also have an economic impact through feeding on the sport fish because that can actually reduce the sport fish, and we have a pretty important economy for recreational fishing in Pennsylvania.
Kara Holsopple: The species is also an issue because of contaminants like PCBs and heavy metals. Why is that?
Sara Stahlman: It’s kind of this process of the food chain and bioaccumulation through the food chain. Like I mentioned earlier, they feed on things like zebra mussels. We have zebra mussel and quagga mussels, which is a cousin. Both are from the same area and both have the same habits. They filter feed, and as they’re filter feeding, they bring in those kinds of heavy metals and contaminants into their fatty tissues and they accumulate there.
Then you have species like round goyi that feed pretty heavily on things like those mussels. They’re bioaccumulating all of those toxins into their tissues. Then the round goby is also preyed upon by sport fish, birds, and it moves up the food chain. So there’s that movement of contaminants up the chain, which in the past has led to botulism outbreaks, fish kills and bird kills.
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Kara Holsopple: You mentioned round goby have been used as bait. That’s not legal. How has round goby spread, and what can anglers do to help prevent that?
Sara Stahlman: It’s not legal to move round goby in Pennsylvania. They’re not meant to be used as bait, but oftentimes they still are. I’ve recently heard the term that anglers use, they’re called “bass candy.” So it’s something that I think anglers find attractive without maybe understanding what a round goby is or the impacts that it can have.
There’s that intentional aspect, but there’s also the fact that there is the possibility that round gobies, when they’re small, look like bait fish. And if you’re not familiar, it can easily get mixed in with what you might think are regular shiner species that you’re using as bait. We ask anglers not to purposely use round gobies as bait, don’t move them around, but also not to dump bait. So, if you’re out fishing somewhere, and you have a bait bucket and you don’t use everything in that bucket, don’t dump that out into a water source. We always ask anglers to dispose of unwanted bait in the trash.
Kara Holsopple: You’re hosting an event with the Pennsylvania Governor’s Invasive Species Council for anglers in December to talk about round goby. What are you hoping to learn from them?
Sara Stahlman: We really want to hear from anglers because we want to be able to create messages and outreach strategies that work for anglers. We don’t want to just come up with things and throw them at a wall and see what sticks. We really want to hear it out of their mouths. Here’s where I get my information. Here’s the type of messages that resonate with me. We want to really understand the culture and the mindset and the values that anglers have so that they can work directly with us to create these strategies that protect the water source that they’re using to fish.
Kara Holsopple: Round goby is already in Lake Erie and all the other Great Lakes and some of Lake Erie’s tributaries in Pennsylvania. Is there something that can be done to reduce their population, or is it more the species not spreading to other waterways?
Sara Stahlman: Once an invasive species becomes established in an area, like how they are like Erie, it becomes very difficult, expensive, and potentially impossible to eradicate populations. It becomes, I think, more of a prevention from spreading to new areas. For example, round goby were introduced into Lake LaBeouf, which has a connection to French Creek. French Creek is a very biodiverse stream with a lot of species and connects down to the Allegheny. We don’t want to see species like round goby impacting some of those highly valuable and diverse streams like French Creek. The impetus for doing this round goby engagement session is really just helping anglers to understand that taking small steps, they can make a huge difference. Invasive species can be moved around by natural ways, that’s always a possibility, but the greatest source and vector of spread for invasive species movement is people.
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Sara Stahlman is extension leader for Pennsylvania Sea Grant. The free event for northwest anglers is on December 6.
Anyone can identify and report round goby to the state if it is seen in a new spot with a mobile app, or call the Pennsylvania Invasive Species Reporting hotline at 1-833-INVASIV.
