Tomas works with different issues of fish biology/ecology and aquatic ecology in general. In his research he often uses hydroacoustics, both applying it as a method to study fish (but not only) and taking part in its development. Previously he worked at Stockholm University, where he studied the offshore wind farms possible effects on the pelagic fish populations the Kalmar Sound, Baltic Sea. He received his PhD at the Dept. of Systems Ecology, Stockholm University in 2005. His thesis focused on the characterization of acoustic properties of the Baltic Sea clupeids (new target strength to fish length relationship, i.e. methodological part) and studies of fish distributions and their behaviour in relation to the physical and biological environment. Before the PhD studies (1995-2001), while working at the Institute of Ecology, Lithuania, he was responsible for the acoustic assessments of pelagic fish stocks in the Baltic Sea, and was also involved in different projects investigating fish and their populations in fresh waters.