Photo credit: Center for Great Lakes and Aquatic Sciences,
University of Michigan, Bugwood.org
Report this Species!
If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.
Species at a Glance
The round goby is a small, aggressive, bottom-dwelling fish that has altered the Great Lakes food web since it was first discovered in Lake St. Clair in 1990. It grows rapidly and reproduces several times in one season. Avian botulism outbreaks appear directly related to the round goby due to its heavy feeding on invasive zebra and quagga mussels.
The two most distinguishing features of the round goby are the black spot on the dorsal fin, and the fused pelvic fin that forms one suction cup-shaped fin. Young round gobies are a solid slate gray, whereas older gobies are mottled with olive green, black, gray, and brown spots. Spawning males turn almost solid black. It has a soft body and a large round head with very distinctive frog-like raised eyes. On average, it grows 10 -25 cm (3.9-9.8 in) in length.
While the round goby looks very similar to the native mottled sculpin (Cottus bairdi), the sculpin has two separated pelvic fins and lacks the black spot on the dorsal fin. The round goby may also resemble the much smaller, invasive tubenose goby (Proterorhinus marmoratus), but the tubenose goby has tubular-shaped nostril extensions and lacks the protruding eyes and the black spot on the first dorsal fin.
This freshwater fish prefers shallow water with rocky and sandy bottoms where it likes to perch on top of rocks and hide in crevices. The round goby can occupy a variety of depths and can tolerate a wide range of temperatures, water quality, and oxygen concentrations. It can also survive in brackish water.
The round goby was most likely introduced to the Great Lakes through the ballast water of ocean-going cargo ships. Because it resembles small baitfish, boaters and fishermen can accidentally carry it from one body of water to another through bait buckets, bilge water, and plant debris.
Native to Eurasia, including the Black, Caspian, and Azov seas and tributaries, the round goby was first sighted in the
St. Clair River in 1990 and has since spread to all of the Great Lakes. It is now working its way inland through rivers and canal systems and can be found in the Mid-Atlantic in select locations in New York and Pennsylvania.
Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.
The round goby is thriving at the expense of native populations, many of which are important sport fish. It outcompetes native species including sculpin, logperch, lake trout, and darters for food sources, habitat, and spawning sites. It also spawns more frequently than its native competitors, and feeds directly on their eggs and young.
Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).