Description of Age-0 Round Goby, <em>Neogobius melanostomus</em> Pallas (Gobiidae), and Ecotone Utilisation in St. Clair Lowland Waters, Ontario

Early developmental stages and ecotone utilisation of the non-indigenous Round Goby, Neogobius melanostomus (Pallas, 1811), are described and illustrated. Fish (5-40 mm) were collected in coarse gravel, rocks and debris in the St. Clair River/Lake system, Ontario, in 1994-2000. The Round Goby hatches at about 5 mm with black eyes, flexed urostyle, and developed fins and digestive system. Distinguishing characters include large head, dorsolateral eyes, large fan-shaped pectoral fins, two dorsal fins, fused thoracic pelvic fins and a distinct black spot on the posterior of the spinous dorsal fin. Modal counts for preanal, postanal, and total myomeres were 12, 19, and 31, respectively.