The ScienceDaily reports that Norwegian researchers have developed an echo sounder that simultaneously emits 100 frequencies. This enables the selective identification of a species of fish or zooplankton for viewing on the echogram or sonogram.
Source: The Research Council of Norway (2012, November 8). Next-generation echo sounder ready. ScienceDaily. Retrieved November 10, 2012, from http://www.sciencedaily.com/releases/2012/11/121108073807.htm