However, Illinois plans to look for them in 1996. Round gobies have a fascinating, and not completely understood, life history. Females mature at one year of age, as small as 58 mm, and spawn every 20 days, up to six times, during the spring. Total fecundity is about 5,000 eggs. The eggs are cone-shaped and adhesive, clinging to rocks and other structure.
Males guard the nests, and turn dark black when spawning.
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.