Cod's Law

Reflective surfaces polarize light, however a recent report found that silvery fish can overcome this basic law of reflection; an adaptation that may help them evade predators. Researchers found that the skin of sardines and herrings contains two types of guanine crystal. By mixing these two chemicals, the fish's skin doesn't polarize the reflected light and thus maintains its high reflectivity. This helps the fish best match the light environment of the open ocean, making them less likely to be seen. These non-polarizing organic reflectors may ultimately find applications with LEDs and low loss optical fibres.