The Round Goby is widespread and there is no evidence of global decline. The overall population remains very large, while expansion of its invasive range is ongoing. It is therefore assessed as Least Concern.

This species is native to coastlines and lower river courses of the Azov, Black, and Caspian sea basins, plus the northern Sea of Marmara. Since the late 20^th century its non-native distribution has increased substantially, particularly in Europe and North America where it is considered a highly invasive species.

This range expansion first took place in rivers draining to the northern Black and Caspian basins during the 1980s, when it was reported from the Moskva River, an upper tributary of the Volga River. It has since moved further upstream to the Rybinsk Reservoir in the Volga, to Orenburg in the Ural River, and to Kiev in the Dnieper River. In addition, it now occurs in most major tributaries of the Danube River, including the upper reaches of the system where it was initially discovered near Vienna (Austria) in 2000 and at Passau (Germany) in 2004.

In the Baltic region it was first recorded at the Gulf of Gdańsk, Poland, in 1990 and has since spread around the majority of the basin. In late 2004, Round Goby individuals were collected from the delta of the Rhine River (Netherlands), and in 2012 from the upper Rhine near Basel (Switzerland). The species was first reported from the Elbe River (Germany) in 2008, the Scheldt and Albert canals (Belgium) in 2010, the Weser River (Germany) in 2012, and the Oder River (Germany and Poland) in 2013. In 2020 it was collected from a tributary of the Maritsa (El. Έβρος (Evros); Tr. Meriç) River in Bulgaria, representing a first record in the Aegean Sea basin.

The Round Goby was first found in the St. Clair River, North America, in 1990. It has since spread throughout the Laurentian Great Lakes system, including a number of tributary rivers plus the outflowing St. Lawrence River downstream to Montreal (Canada) and the Illinois River, a tributary of the Mississippi River to which it arrived via the Chicago Sanitary and Ship Canal.

This species' global population trend has not been quantified, but it remains abundant within its native range. There is no evidence to suggest any decline, and its global population is increasing due to expansion beyond its natural range.

This benthic, euryhaline species inhabits both freshwater and brackish habitats including shorelines, estuaries, larger river channels, backwaters, littoral lagoons, inland lakes and artificial reservoirs. Although it has been recorded in fast-flowing submontane stretches and open areas with fine substrates, it exhibits a preference for lowland environments with sluggish current, rocky or otherwise hard substrata, and abundant aquatic vegetation or other submerged structures. It is an opportunistic predator feeding on aquatic invertebrates and smaller fishes, often specialising on bivalve molluscs when available. Larger individuals are territorial and aggressively defend the most favourable sites for foraging, spawning, and predator avoidance.

Its typical lifespan is four years, with sexual maturity achieved at around 2-3 years of age. Spawning typically occurs from April to September. Adult females are capable of multiple spawning events within a single season, during which reproductive male individuals are identified by their darkened colouration. The adhesive eggs are deposited on or beneath stones, shells or aquatic plants, and parental males guard them until they hatch.

The Round Goby's expansion into areas outside its natural range is believed to have been driven by multiple introduction events through port-to-port transport in ship ballast water. In Europe, it was first recorded in the vicinity of important river ports located on large, navigable rivers connected to the Black Sea such as the Volga, Danube, and Dnieper, plus the network of artificial canals connecting them. It was then able to spread further via downstream drift of age-0 juveniles, while upstream migration has apparently been aided by the presence of rip-rap bank stabilisation along channelised river stretches in addition to construction of industrial harbours, artificial canals and reservoirs. Genetic analyses suggest that ships from the Black Sea are also likely to have introduced the species to the Baltic Sea and North America. These processes are believed to be ongoing.

In addition, larval round gobies undertake a diel vertical migration to feed nocturnally on zooplankton at or near the water surface, favouring them being pumped into ballast water and dispersed elsewhere. A largely untested hypothesis also suggests that adult individuals may actively exploit ship hulls as foraging or spawning habitat, and that this may represent a supplementary translocation vector. Some shorter-range dispersals have also been facilitated by recreational anglers, with the fish released unintentionally while being used as live bait. Furthermore, this species is widely-acknowledged to possesses a series of biological traits that ease colonisation of novel environments, including the ability to tolerate a wide range of ecological conditions, a broad diet, aggressive behaviour, an extended spawning period, specialised male parental care which favours recruitment, and a large body size compared to other benthic freshwater fishes.

Introduction of the Round Goby is associated with a range of negative ecological consequences throughout its non-native range, including changes in entire food webs. It is now the most abundant fish species in many coastal areas of the Baltic Sea basin and has been linked to declines in a number of native fish and bivalve species, including Baltic Flounder (Platichthys solemdali), Black Goby (Gobius niger), and Blue Mussel (Mytilus edulis). Conversely, it has also become an important component of the diet for commercial fish species such as Atlantic Cod (Gadus morhua), Turbot (Scophthalmus maximus), and European Perch (Perca fluviatilis), plus fish-eating birds including the Great Cormorant (Phalacrocorax carbo) and the Grey Heron (Ardea cinerea).

In European rivers, the Round Goby has been linked to declines in a number of native fishes and invertebrates, and emerging evidence suggests it may be a vector for contagious fish diseases such as Koi herpesvirus.

In the Great Lakes region, deteriorating native fish numbers have been associated with local Round Goby abundance, since it is believed to prey on their eggs and fry while competing with them for food, spawning sites and other resources. Comparable declines in aquatic invertebrate communities have also been noted at some sites. It has also been tentatively proposed as a vector for viral haemorrhagic septicaemia in fishes, avian botulism in migratory birds, and polychlorinated biphenyls in trophic webs, often through linkages with the invasive zebra mussel (Dreissena polymorpha) and Quagga Mussel (Dreissena bugensis). Moreover, there is strong evidence to suggest that the trophic relationships between these dreissenid mussels, the Round Goby, and the invasive amphipod Echinogammarus ischnus demonstrate that they actively further each other's advancement in novel environments. Increased predation on Round Goby by double-crested cormorant (Nannopterum auritum) has been linked to reduced reproductive success due to its lower energy density compared with native fish species, although this may also contribute towards ongoing cormorant population management efforts.

Positive effects of Round Goby introduction in the Great Lakes include recovery of the locally-threatened Erie water snake (Nerodia sipedon insularum) population, for which it has come to comprise the majority of the diet. It may also have played a significant role in improving population growth of the Endangered lake sturgeon (Acipenser fulvescens) in Lake Ontario and the lower Niagara River. It is also an important prey item for a number of economically-important sport fishes, including Walleye (Sander vitreus), Yellow Perch (Perca flavescens), Largemouth Bass (Micropterus salmoides), Smallmouth Bass (Micropterus dolomieu), and Lake Trout (Salvelinus namaycush).

This species is not believed to be at risk from any particular threats, and research suggests that its non-native range expansion has in fact been favoured by anthropogenic river modification.

The Round Goby is exploited by commercial fisheries within its native range, where it is marketed as a food fish for human consumption.

In its non-native range, a commercial fishery has developed in Latvia where more than 1,000 tonnes was landed in 2018. It is also considered to be potentially valuable elsewhere, with efforts underway to develop processed products from its flesh in Denmark and Sweden, for example.

It is targeted by recreational anglers in some areas, but regarded as bycatch in others.

No species-specific conservation measures are in place, and in the species' non-native range management efforts have centred on preventing further spread. For example, a lock on the Fox River in Wisconsin, United States, is permanently closed to boats in order to prevent upstream migration of round gobies into Lake Winnebago.