8. One factor that causes the breakdown of heme to biliverdin is exposure to ultraviolet (UV) radiation from the sun. The earth is normally protected from UV radiation by ozone in the upper atmosphere. In recent years ozone "holes" have been noted over both the north and south poles as a result of CFCs (chlorofluorocarbons) entering the atmosphere. In some species of animals, biliverdin is known to act as a photo-protectant.
9. It is possible that walleye in Canada use, as a sun screen, the very chemical which forms in their blood from exposure to too much sun. This conclusion is still only speculation but it is our best hypothesis.
Interesting, the amount UV radiation can vary as much as 20% based on the solar sun spot cycle, with increasing sunspots activity in the current cycle we should see increased UV radiation over the next few years with the next solar maximum peaking in 2013. Keep in mind this is not expected to be a very strong solar cycle, in fact the the solar minimum we are just coming out was a century class event.
