Round Goby

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.

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.

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, zebra mussels, insect larvae, and other small invertebrates (insects and amphipods) living on the bottom of lakes and streams. In spring, the main elements of their diet in the Sasyk Lagoon are Hydrobia, Cerastoderma, and Abra. 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. Near Sevastopol, the round goby feeds on molluscs (Mytilaster lineatus and Abra sp.). In the Baltic Sea, they impact Mytilus edulis populations.

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.