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.
Communication Channels: visual
Perception Channels: visual ; tactile ; chemical
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Range length: 11 to 30 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger
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.
Average lifespan
Status: wild: 4 years.
Average lifespan
Status: captivity: 4 years.
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.
Range depth: 0 to 30 m.
Habitat Regions: temperate ; freshwater
Aquatic Biomes: lakes and ponds; rivers and streams; brackish water
Round gobies are native to the Black, Caspian, Marmara, and Azov Seas and their tributaries in Eurasia.
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.
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.
Biogeographic Regions: nearctic (Introduced ); palearctic (Introduced , Native )
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.
Animal Foods: fish; eggs; insects; mollusks; aquatic crustaceans
Primary Diet: carnivore (Insectivore , Molluscivore )
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.
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.
There is almost no larval stage in the development of round gobies. Eggs take up to 18 days to hatch.
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.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
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.
Males guard nests and attract females to spawn there. Multiple females may leave their eggs in a single male's nest. In some introduced populations, there is an extremely skewed sex ratio, with 2 to 3 males for every female. In native populations the sex ratio is roughly equal.
Mating System: polygynous
Female round gobies spawn repeatedly, approximately every 20 days, from April until September while males guard the eggs and young. This repeated spawning gives them an ecological advantage over species which spawn less frequently. Females are mature by 2 to 3 years of age and males at 3 to 4 years. Females deposit 89 to 3841 eggs at a time. Fecundity is directly related to female body size. Eggs are laid on a hard substrate, such as gravel, rocks, or even submerged trash, and are then guarded by the male until hatching.
Breeding interval: Female round gobies can spawn every 20 days during the warm season, from April to September.
Breeding season: Spawning occurs from April to September.
Range number of offspring: 89 to 3841.
Range gestation period: 18 (high) days.
Range age at sexual or reproductive maturity (female): 2 to 3 years.
Range age at sexual or reproductive maturity (male): 3 to 4 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
Males aggressively guard eggs at nest sites until they hatch.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Male)
The round goby (Neogobius melanostomus), a native of freshwater and marine waters of Eurasia (particularly the Black and Caspian Seas and the Sea of Azov), was first observed in the Great Lakes Basin in 1990 when recreational anglers caught a specimen in the St. Clair River. It is believed that the species was introduced via international shipping ballast water discharge. Since that time, the fish has spread to all of the Great Lakes (Lake Erie, 1993; Lake St. Clair, 1994; Lake Michigan, 1994; Lake Superior, 1995; Lake Ontario, 1996; Lake Huron, 1998), where it is undergoing a dramatic population explosion (densities of several dozen per square meter of lakebed have been reported). Spread upstream to Lake Superior is believed to have been a result of interlake ballast water transport; downstream spread is most likely attributable to both ballast discharge and natural migration. Round gobies may prey on small fish such as darters, as well as lake trout, sculpin, and darter eggs and fry.
Adult gobies take over prime nearshore spawning sites and aggressively prevent use by native species. Long-term impacts are expected to include declines in native species populations. N. melanostomus has a well-developed lateral line which may give it a competitive advantage over native species feeding in turbid waters. Round gobies are also prolific breeders, spawning every 20 days during the spawning season.
Round gobies are problematic to anglers in that gobies are proficient bait thieves.
Neogobius melanostomus has the beneficial impact of consuming large numbers of zebra mussels; however, given the contamination found in some populations of zebra mussels, this may result in bioaccumulation of toxics in gobies and biomagnification up the food chain to shorebirds and other species which consume the fish.
The round goby (Neogobius melanostomus) is a fish. Defined as a euryhaline bottom-dwelling goby of the family Gobiidae, it is native to Central Eurasia, including the Black Sea and the Caspian Sea. Round gobies have established large non-native populations in the Baltic Sea, several major Eurasian rivers, and the North American Great Lakes.[2]
Round gobies are small, soft-bodied fish characterized by a distinctive black spot on the first dorsal fin. The eyes are large and protrude slightly from the top of the head and, like most gobies, the pelvic fins are fused to form a single disc (shaped like a suction cup) on the belly. Round gobies range in length from 10 to 25 centimetres (4 to 10 inches), with a maximum size of 24.6 cm (9.7 in). They weigh between 5.0 and 79.8 grams (0.176 and 2.816 ounces), their weight increasing with age. Male round gobies are larger than females. Juvenile round gobies (less than one year old) are grey. Upon maturation, round gobies become mottled with grey, black, brown, and olive green markings. Adult male round gobies turn inky black during the spawning season and develop swollen cheeks. Male and female round gobies are easily differentiated by the shape of their urogenital papilla, which in males is white to grey and long and pointed and in females is brown, short, and blunt-tipped.
Round gobies are widespread in the Sea of Marmara and in the rivers of its basin and can also be found in the Black Sea and the Sea of Azov, along all coasts and fresh waters of their basins as well as in the coastal lakes and lagoons. They are also found in the rivers of Crimea and the Caucasus (Mezib, Pshada, Vulan, Kodori, and Çoruh) and in the Caspian Sea, represented by subspecies Neogobius melanostomus affinis.
Since 1990, the round goby has been registered as introduced in the North American Great Lakes, in parts of Europe, and in the Baltic Sea as an invasive species.[3] The first catch in North America was documented by Jude et al 1992 and Crossman et al 1992, caught by an angler in Sarnia, Ontario, fishing the St. Clair River on June 28, 1990. The studies of Jude, Crossman, together with Jude et al 1995 found a range of sizes between 29 and 180 millimetres (1+1⁄8 and 7+1⁄8 in) in the St. Clair.[4] Round gobies are also rapidly expanding into tributaries of the Great Lakes in North America and were recently discovered in at least one of the Finger Lakes in New York State (Cayuga Lake) and the first round goby was discovered by the state of New York in the Hudson River in 2021.
Round gobies are euryhaline (salt-tolerant) and live in both freshwater and marine ecosystems, up to a mineralization of 18–24%. They are commonly found on continental shelves with sandy and rocky bottoms with low silting at depths from 1–2 m (3.3–6.6 ft) to 10–17 m (33–56 ft).
Round gobies actively feed both nocturnally and diurnally and are believed to detect prey only while stationary. The primary diet of round gobies includes mollusks, crustaceans, worms, fish eggs, zebra mussels, small fish, insect larvae, and other small invertebrates (insects and amphipods) living on the bottom of lakes and streams.[2] In spring, the main elements of their diet in the Sasyk Lagoon are Hydrobia, Cerastoderma, and Abra.[5] In the same season, near the Romanian coasts of the Black Sea, the round goby feeds on polychaetes, crustaceans (Idotea balthica, Pachygrapsus marmoratus, Xantho poressa, etc.), and juvenile gobies.[6] Near Sevastopol, the round goby feeds on molluscs (Mytilaster lineatus and Abra sp.).[7]
In the Gulf of Odessa, twenty-three items are identified in the diet of the round goby;[8] Mytilus galloprovincialis, Setia pulcherrima, Mytilaster lineatus, Lentidium mediterraneum, Idotea balthica, and Alitta (Nereis) succinea dominate in the spring, while in the summer, the diet consists mainly of Sphaeroma pulchellum and L. mediterraneum. The mussels M. galloprovincialis and M. lineatus are important in all seasons.
Female round gobies reach sexual maturity in one to two years while males do so in three to four years. Gobies in the Laurentian Great Lakes typically mature up to one year earlier than in their native habitat in Europe. Females can spawn up to six times during the spawning season, which spans April to September in most areas.
Males will migrate from deeper water, where overwintering occurs, into shallower breeding grounds during the beginning of the mating season. They then release a steroid sex pheromone that attracts females to their territory. Males also use visual displays, including posturing and changing color from beige to black during mating season, and can produce sounds during courtship. The females deposit their eggs in male-guarded crevices between rocks. Eggs are 4 by 2.2 mm (0.157 by 0.087 in) in size, while egg clutches can contain up to five thousand eggs. Males are territorial and will defend eggs from predators as well as continuously fan them to provide the developing embryos with oxygenated water. This results in successful hatch rates of up to 95%.
The species was accidentally introduced into the North American Great Lakes by way of ballast water transfer in cargo ships. First discovered in North America in the St. Clair River in 1990, the round goby is considered an invasive species with significant ecological and economic impact;[9] the consequences of introduction are quite complex as the fish both competes with native species and provides an abundant source of food for them while consuming other invasive species.[10] In other words, the round goby behaves much like most biological invasive controls. An aggressive fish, the round goby outcompetes native species such as the sculpin and logperch for food (such as snails and mussels), shelter, and nesting sites, substantially reducing their numbers. Round gobies are also voracious predators of eggs of native fish, many of them important to the angling industry. The goby's robust ability to survive in degraded environmental conditions has helped to increase its competitive advantage compared to native species.
Many native predatory fish such as smallmouth bass, largemouth bass, walleye, salmon, and trout have begun to prey on round gobies. The incorporation of the round goby into native foodwebs, coupled with the goby's ability to consume large numbers of invasive mussels (zebra and quagga), may result in greater bioaccumulation of toxins such as PCBs higher in the food chain, since these mussels filter-feed and are known to accumulate persistent contaminants. However, this is partly beneficial because even though they do not reduce the population of zebra mussels, they do control their population. Hence, it prevents a large-scale spread of the zebra mussel, which is also an invasive species in the Great Lakes. Another unintended benefit of the round goby's introduction is that the Lake Erie watersnake, once listed as a threatened species, has found the goby to be a tasty addition to its diet. A recent study found the introduced fish now accounts for up to 90% of the snake's diet. The new food supply means that the water snake is now staging a comeback.[11] Round gobies also serve as food for a variety of predatory fishes in the Great Lakes, including bass, lake trout, lake whitefish, burbot, lake sturgeon, and walleye.[12]
The round goby is also considered invasive in parts of Europe. This process was started by its introduction to the Gulf of Gdańsk (southern Baltic Sea) in 1990.[13] Locations recently invaded by round gobies include the Aegean Sea,[14] different parts of the Baltic Sea,[15] the North Sea basin,[16] and the Danube and Rhine basins.[17][18] In the German part of the Baltic Sea this fish was first noted near Rügen Island.[19] It is now distributed all along the southwestern Baltic Sea coast, including Stettiner Haff (Szczecin Lagoon), the Unterwarnow (Warnow river estuary), the mouth of the Trave, and the Nord-Ostsee (Kiel) Canal.
As of 2010, the westernmost site of round goby occurrence in Europe was the lower Scheldt, including the tidal zone in the river mouth, and Albert Canal, Belgium.[20] In 2011, the round goby began invading the fresh waters of France; the species appeared in the Rhine River (on the border between France and Germany) and in the French part of the Moselle River.[21]
In total, fifty-two parasite species are registered in the round goby in its native area.[22] The most abundant parasites of the Black Sea round goby are metacercariae of trematodes of the Heterophyidae family, such as Cryptocotyle concavum, C. lingua, and Pygidiopsis genata.[23] The trematodes C. lingua and P. genata can infest humans.[24][25] In the 1950s, along the coast of the Gulf of Taganrog (Sea of Azov), the round goby was registered as a host of epizootic nematodes Tetrameres fissispina and Streptocara crassicauda, which were fatal to ducklings.[26]
In the Gulf of Gdańsk, Baltic Sea, the parasites of the invasive round goby consist of twelve species.[27] The core of the parasite fauna comprises two species of trematode metacercariae: C. concavum and Diplostomum spathaceum. Also in the Baltic Sea, the round goby is a paratenic host of the invasive nematode Anguillicoloides crassus.[28] In the Vistula Lagoon, the most abundant parasites of the round goby are nematodes Hysterothylacium aduncum and Anguillicoloides crassus.[29]
Twenty-five species of parasites are noted in the round goby in the American Great Lakes.[30][31][32][33] The trematode D. spathaceum is the most abundant core species overall, while the cestode Proteocephalus sp. and the trematode Neochasmus umbellus are also well represented. The round goby may prevent some of the metacercariae of N. umbellus from completing their life cycle.[34] The parasite "load" on the invasive gobies in the Great Lakes appears relatively low in comparison with their native habitats, lending support to the "enemy release hypothesis".
The round goby (Neogobius melanostomus) is a fish. Defined as a euryhaline bottom-dwelling goby of the family Gobiidae, it is native to Central Eurasia, including the Black Sea and the Caspian Sea. Round gobies have established large non-native populations in the Baltic Sea, several major Eurasian rivers, and the North American Great Lakes.
