A recent research has found out that fishes communicate in the deep blue seas with their red signals. Some fishes have fluorescent cells which absorb blue light from the bluish grey surroundings of the deep sea, and emit it as red light. The ecological significance of this mechanism has been studied and published in the magazine- Frontiers in Ecology and Evolution.
The research head Professor Nico Michiels and his team of biologists from the University of Tübingen's Institute of Evolution and Ecology studied over 600 species of fishes to screen their red fluorescence production capacity. Upon comparing those fishes against their ecological functions, three important functions of their red light were found.
The first is that, predators like flatfish and scorpion fish have fluorescent lights unevenly distributed over their bodies. This camouflages them against a substrate with lots of red fluorescent algae. The second is that, plankton eaters have red fluorescent rings surrounding their eyes. This helps them find their tiny transparent prey better. The third is that, in fish species in which males and females have different colors, males use their red fluorescent fins to send courtship signals.