After seeing an article about a woman being killed by a ray jumping out of the water and striking her head (http://www.cnn.com/2008/US/03/21/eagleray/index.html?imw=Y&iref=mpstoryemail), I want to delve into the reasons fish jump.
A Great White Shark Leaping for Dinner
There are several “scientific-based” reasons for fish jumping out of the water. The first possible reason is that they are trying to loosen the eggs in their skeins prior to spawning. Another possible reason is that they are trying to rid themselves of sea-lice. The first hypothesis however is probably not true. Based on that logic, every jumping fish is a pregnant female.
The more likely reason is that they simply want to move around something that obtrudes their desired path. Salmon will leap up waterfalls to arrive at the freshwater water sources where they can mate and spawn. Sharks will leap in the air to catch the agile seals they are hunting. Some scientists also believe that jumping may serve a purpose in courtship and dominance rituals for dolphins, killer whales, and belugas (not fish, but aquatic life none-the-less. Those who can jump higher are stronger and more fit to be a father or group leader. Jumping and crashing back into the water may also be akin to scratching for some fish, which dislodges certain parasites like remoras and other copepods that attach themselves to the skin of whales sharks, and other large fish. So even though nobody really knows why this phenomenon occurs, you now have something cool to say to your buddy on your next fishing trip.