Boat users around Geelong and the Bellarine are being warned to watch out for seals, after the death of a fur seal on Port Phillip Bay.

The body was discovered earlier this week and an autopsy has found it had suffered a blunt force trauma to the head - most likely caused by a boat.

GLEN SHARPE from the Department of Sustainability and Environment says people in boats should not go anywhere near seals:

Picture: A colony of Australian fur seals on Port Phillip Bay