Here’s a nice article By Amanda Schaffer (NY Times, May 28, 2012) that summarizes new research about how fish detect the presence of predators. It’s really quite cool, and a little bizarre. Keep in mind the concept of umwelt, and imagine what it might be like if we sensed our world in a similar manner.
When one fish is injured, others nearby may dart, freeze, huddle, swim to the bottom or leap from the water. The other fish know that their school mate has been harmed. But how? In the 1930s, Karl von Frisch, the famous ethologist, noted this behavior in minnows. He theorized that injured fish release a substance that is transmitted by smell and causes alarm. But Dr. von Frisch never identified the chemical composition of the signal. He just called it schreckstoff, or “scary stuff.”