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characteristics
Round gobies are small, soft-bodied fish, characterized by a distinctive black spot on the first dorsal fin. Their eyes are large and protrude slightly from the top of the head and, like most gobies, round gobies have pelvic fins which are fused into a single pelvic suction disc on the belly of the fish. Round gobies range in length from 4 to 10 inches (maximum of 9.7 inches


Feeding/Habitat
Round gobies usually feed nocturnally (but have been observed to feed diurnally as well) and are believed to detect prey only while stationary. The primary diet of round gobies includes mollusks, crustaceans, worms, fish eggs, small fish, and insect larvae. Round gobies are native to the Ponto-Caspian region of Europe, but are now considered an invasive species in the North American Great Lakes (where the first round goby was detected, in the St. Clair River, in 1990) and newly colonized regions of Europe such as the Gulf of Gdansk


reproduction
Round gobies exhibit male parental care. Females can spawn up to six times during the spawning season, which spans April to September. Males will migrate from the deeper water, where overwintering occurs, into shallower breeding grounds during the beginning of the mating season. The males are territoral and will guard nests of eggs and newly hatched young, resulting in successful hatch rates of up to 95%. Its eggs are 4 mm by 2.2 mm in size. Female round gobies reach sexual maturity in 1 to 2 years while males do so in 3 to 4 years