The population of common seals in the UK cannot be estimated very accurately but humans have historically hunted the common seal in great numbers. The Seal Conservation Act of 1970 gives a degree of protection as shooting is outlawed during the breeding season, however if a seal is deemed to be interfering with fishing nets, it can legally be shot at any time under the 'Fisheries Defence Clause' (5). In 1988 a disease caused by the newly emerged phocine distemper virus killed about 3,000 of the UK's common seals. Such drastic population crashes seem to be a natural occurrence, and little can be done to prevent them (3). Common seals are also susceptible to oil and chemical pollutants (3).