Neogobius melanostomus
round goby

A native species to the Black and Caspian Seas, which are located between Turkey and Russia, it is an invasive species in the Great Lakes region of North America.

Bottom dwellers in the nearshore region of lakes and in rivers, gobies prefer rocky habitat that provides lots of hiding opportunities.

Able to survive extremely degraded water quality, they can live in areas where other fish have been pushed out by pollution. They can also withstand low oxygen concentrations, which makes them good species for ballast water transfer introductions, the leading pathway of aquatic invasives.

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. They also usually have a distinctive black spot on their front dorsal fin. Mature gobies are covered by black and brown splotches that lighten in color when threatened. 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 (Jude 1995).

A characteristic of the family Gobiidae is the absence of a swim bladder, which is used for buoyancy control.

Round Gobies are extremely aggresive and vicious fish for their size. Social loners, they will kill or drive other species from a habitat in order to move in. Once there, they will aggressively defend their spawning nests.

Their swimming is characterized by short "hops" between hiding places, as a result of their lacking a swim bladder (Jude 1995).

Their hops and blotchy coloration are defenses against the larger fish that prey on them.

Round gobies are voracious feeders, with a penchant for stealing the worms off an angler's hook. They also prey on zebra mussels, another Great Lakes exotic from the same native region. Young and eggs of other fishes, and even their own, as well as aquatic insects and invertebrates are choice prey. A complete lateral line system (a sensory system) allows them to feed in complete darkness (Jude 1995).

As it often eats bivalves that filter the water, the round goby is a vector for bioaccumulation of many contaminants. The contaminants that build up in the goby are passed on to larger game fish that prey on the goby and then possibly on to humans (Ghedotti et al. 1995).

They also drive native species out of preferred habitat and cause annoyance to anglers who lose their bait to them.

In its native region of the Black and Caspian Seas, the goby is a prey fish for economically important food fishes, and is also fished for food. In the Great Lakes, it feeds on zebra mussels, another exotic species that causes a host of problems. It does not reduce the concentration enough to control the mussels though (Ghedotti et al. 1995).

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