Neogobius melanostomus
round goby

Round gobies are native to the Black, Caspian, Marmara, and Azov Seas and their tributaries in Eurasia. (Fuller, Benson, and Maynard, 2007; Jude, 1995; Marsden and Jude, 1995; Pascualita, 2008; Sapota, 2006)

Round gobies have been introduced in several areas outside of their native range. They are an invasive species in the Great Lakes region of North America, with a rapidly expanding range there. Round gobies are beginning to enter the river drainages of the Great Lakes, including the Chicago River, eventually resulting in the invasion of the Mississippi River drainage. (Sapota, 2006)

They have also been introduced into the Moscow River and the Baltic Sea. They are especially problematic in the Gulf of Gdansk, where populations densities have exploded, but they have been subsequently found in many parts of the Baltic Sea and into the Danube River. It is not clear how round gobies were introduced to the Baltic Sea. (Sapota, 2006)

Bottom dwellers in the nearshore region of lakes and in rivers, round gobies prefer rocky habitats that provide lots of hiding opportunities. These habitats also include areas with sunken objects, piers, and mussel beds. Round gobies can be found in fresh or brackish water and at depths of 0 to 30 meters. They can survive in water temperatures of 0 to 30 degrees Celsius, but tend to thrive in warmer waters. Round gobies are able to survive in areas with poor water quality. They can also withstand low oxygen concentrations. Both of these qualities made them well-suited to surviving in ballast water, which is how they were introduced in the Great Lakes. (Fuller, Benson, and Maynard, 2007; Jude, 1995; Marsden and Jude, 1995; Pascualita, 2008; Sapota, 2006)

Typically under 18 centimeters in length, but with some individuals reaching 30 centimeters, round gobies have large frog-like heads with raised eyes, soft bodies, and spineless dorsal fins. Males are generally larger than females, although size varies regionally. They also have a distinctive black spot on their front dorsal fin. Mature round gobies are covered by black and brown splotches that lighten in color when threatened. Round gobies are distinguished from sculpins of similar appearance by their fused pelvic fin, which is characteristic of the family Gobiidae. This fused fin is also called a suctorial disc and is used to help attach to a surface in flowing water. A characteristic of the family Gobiidae is the absence of a swim bladder, which is used for buoyancy control. Round gobies can be confused with native black gobies in the Baltic Sea. (Jude, 1995; Pascualita, 2008; Sapota, 2006)

There is almost no larval stage in the development of round gobies. Eggs take up to 18 days to hatch. (Sapota, 2006)

Maximum reported lifespan in round gobies is 4 years. After males defend their nests during the breeding season, they die. Females can live to about 3 years old. (Pascualita, 2008; Sapota, 2006)

Round gobies are extremely aggressive fish for their size. They will attack other fish to drive them away from an area and defend spawning areas aggressively. They are solitary, although they may occur at very high densities. They do not travel far, generally staying in one place. Their swimming is characterized by short, darting movements, making it look as if they are "hopping" between hiding places. They lack a swim bladder, so generally stay near the bottom of the water. They may make very small, local migrations to deeper water in fall and back to shallow water in spring, but these migrations are only up to several kilometers in length. (Jude, 1995; Pascualita, 2008; Sapota, 2006)

Home Range

Round gobies remain in very small home ranges.

Round gobies, like most other fish, use visual and chemical cues in communication. They have a complete lateral line system that helps them to hunt in dark water or at night. (Sapota, 2006)

Round gobies are voracious feeders, with a penchant for stealing bait off the hooks of anglers. They eat mussels and other mollusks, with up to 60% of their diet made up of mussels in some places. They also eat aquatic insect larvae and the young and eggs of other fish. In the Baltic Sea they impact blue mussels populations. In the Great Lakes they prey on zebra mussels, another Great Lakes exotic from the same native region. A complete lateral line system allows them to feed in complete darkness. In the Great Lakes they also eat the young and eggs of mottled sculpin, logperch, darter species, and lake trout, among other species, making them a threat to those native populations. (Fuller, Benson, and Maynard, 2007; Ghedotti, Smihula, and Smith, 1995; Jude, 1995; Marsden and Jude, 1995; Pascualita, 2008; Sapota, 2006)

Their hop-like swimming style and blotchy coloration that helps them blend in with their surroundings are defenses against predators. Round gobies are eaten by large, predatory fish, such as walleye, and diving and wading birds. In the Baltic Sea they are important prey for great cormorants. (Jude, 1995; Sapota, 2006)

Round gobies compete with native species where they are introduced. In the Great Lakes, they compete directly with similar fish, such as mottled sculpin, which they completely displace from spawning and foraging areas. They also compete with, and eat the young and eggs of, logperch and darter species. In the Baltic Sea they compete with three-spined sticklebacks, flounder, and viviparous blennies. (Fuller, Benson, and Maynard, 2007; Marsden and Jude, 1995; Pascualita, 2008; Sapota, 2006)

Because round gobies often eats bivalves that filter the water, they are vectors for bioaccumulation of many contaminants. The contaminants that build up in round gobies are passed on to larger game fish and then possibly on to humans. Round gobies are a threat to native fish species, which they drive out of preferred habitat and compete directly for prey. Round gobies are a nuisance to anglers who lose their bait to them. (Ghedotti, Smihula, and Smith, 1995)

In its native region of the Black and Caspian Seas, round gobies are prey fish for economically important food fishes, and are also fished for food. In the Great Lakes, they feed on zebra mussels, another exotic species that causes a host of problems. It does not reduce the concentration enough to control these mussels, though. (Ghedotti, Smihula, and Smith, 1995)

As an invasive species in the United States, efforts to reduce round goby populations are underway. They have no special status in their native range, though their cousins, tubenose gobies, which are also invasive in the Great Lakes, are endangered in the Black Sea region. (Jude, 1995)