[1] Žulkus started his career as an archaeologist in the Institute for Monument Preservation in Klaipėda.
From 1969 till 1990 he was fellowship of the institute (from 1979 in position of head of archaeologists group) and investigated mainly the old town and the castle ruin in Klaipėda.
In 1988, after studying in Institute of Archaeology of the USSR Academy of Sciences, he defended his doctoral thesis on Klaipėda and the region in the 11th - 17th centuries.
He originated the underwater archaeology research in Lithuania and in 1999 defended his habilitated doctoral thesis on the role of Curonians in the culture and society of Western Balts in the Iron Age.
In 2009 he was designated a member of the scientific and technical advisory body of the UNESCO Convention on the Protection of the Underwater Cultural Heritage.