round goby is an aggressive feeder that spread quickly throughout the
Great Lakes basin. This small, bottom-dwelling fish is even capable of
foraging in total darkness!
The round goby was probably first introduced to the Great Lakes by hitching
a ride in the ballast water of ships traveling from its native range in the Ponto-Caspian
basin of Eurasia (Eastern Europe and Western Asia).
Gobies are bottom dwelling animals that prefer rocky cobbles in shallow
water. They have a voracious appetite and feed on a wide variety of prey including small worms, aquatic
insects, fish eggs, fish fry, and zebra mussels; about 70% of their diet is composed of zebra
While round gobies can reach 25 cm (10 in) in length, Great Lakes adults
are usually less than 18 cm (7 in) long. Female and immature male gobies
gray and brown markings and spawning males turn almost solid black. Round
gobies have a soft body with prominent eyes near the top of a round head
and a unique single pelvic fin on their ventral
side. Their body shape is similar to our native sculpin.
Once introduced, the round goby population exploded and has expanded rapidly
into all the Great Lakes. The round goby has now spread from the Great
Lakes into many other waterways, including the Mississippi River.
2010 Distribution of the Round Goby
When round gobies compete with native fish for habitat and spawning sites,
they can dramatically reduce native fish populations, particularly bottom-dwelling
fish, like mottled sculpin, log perch, and darters. In addition, the goby
is a highly prolific breeder that can spawn as many as five times a season
from April to September.
Round gobies can easily be introduced into new bodies of water as hitchhikers
in bait wells, bait buckets, and ballast water. The strongest defense
against spreading gobies to new locations is education.
To read more, view the Pennsylvania Sea Grant round goby fact sheet.
FOR MORE INFORMATION ON THE ROUND GOBY