Males are said to die after spawning, but this may not always be the case. Males can live to be 5-6 years old. Round gobies are benthic throughout their life, even when newly hatched. Their pharyngeal teeth are ideal for crushing shells. They are selective for small zebra mussels, less than 9 mm in length.
Round gobies eat some fish, and are cannibalistic.
Many fish eat round gobies, especially smallmouth bass. Male and female round gobies can generally be externally distinguished by their genital papillae. This appears to be unique in the species. Round gobies are difficult or impossible to age by scales, but Ohio State biologists think it can be done if one looks at many scales from a specimen. There is concern that the lake subspecies of mottled sculpin may be driven to extinction.