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Invasive Species: What is a Round Goby?

There are plants and animals that belong in an area, but invasive species are plants or animals that are brought into that area. They compete with the local plants and animals and take over. They're invasive.

The round goby is a small fish: between 6 to 20 centimeters, which is about 2 to 8 inches. But this small fish makes a big impression. Why's that? Well, the round goby it lays a lot of eggs. People can have maybe one baby a year; but the goby lays FIVE THOUSAND EGGS, six times a year!

Then, all these round gobies are aggressive and eat lots of food. This leaves less food for native fish like the sculpin. The goby also eats shellfish like mussels. The goby also eats the eggs of native fish. So it's not only laying a lot of eggs, it is eating other fishes' eggs! This means more round gobies, and less other fish.

How can you tell an invasive round goby from a native sculpin?

They are both small and kind of look like sand. But the goby has:
  • More raised eyes
  • Scales with darker spots
  • And a really noticeable black spot on its top dorsal fin.
In mating season the males turn dark olive green, almost black. The goby is also the only fish in the Great lakes with a single pelvic fin – it's like a little suction cup to hold them to rocks, but that means you'd have to turn it over... ewwww.

How did they get here?

Well, little sea creatures get moved around in the ballast water of the big cargo ships. The round goby came from the Black Sea in Eastern Europe, and hitchhiked in boats all the way to the Great Lakes.

Gobies are now in all five Great Lakes, the Saint Lawrence River, the Ottawa River, and many others. They're invading! And because there are so many gobies feeding on so many mussels, they can also pass disease like botulism to other fish and birds

If you find a round goby, you can not keep it! You can not throw it back! You can not use it as bait for fishing! You have to destroy it.

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