Shag - Shags and humans

Numbers of shags appear to have been increasing, especially on the east coast of Britain, since the 1920s. There are about four times as many shags as there are cormorants. This boom in population is probably due to a decrease in human's persecution (they used to be killed by fishermen) and climatic changes improving the food supply. Unfortunately since 2000 shag populations have been becreasing all over the UK. This could be caused by over fishing decreasing the Shags food sources.

On occasions local populations of shags are reduced as a result of a natural cause - a poison produced by tiny pinkish sea creatures (dinoflagellates); these creatures can be so numerous that they colour the water in a “red tide”.