Complex sentence: The grass goby is commercial fish in the Black Sea and the Sea of Azov, the Molochnyi Estuary, Tuzly's Lagoons and in the Sivash.
Split into simpler sentences: The grass goby is commercial fish in the Black Sea and the Sea of Azov. It is fish in the Molochnyi Estuary, Tuzly's Lagoons, and in the Sivash.