Dr. Rostad a marine biologist and have specialized in fish and zooplankton ecology with the use of scientific echo sounders as the main tool. This involves mainly behavior and abundance studies of fish and zooplankton, but he has also used echo sounders to record sinking polluted sediments and direct carbon vertical flux. Most of his work has been with stationary echo sounders, which are used for long term monitoring in ocean observatories. Recently he has been mainly studying mesopelagic fish; the most abundant fishes in the world, and their role in vertical flux of carbon in the world's oceans.

Marine ecology Acoustics Ocean vertical carbon flux Mesopelagic fish