An Australian fur seal which hauled itself out of the North Esk River at St Leonards dog park was likely chasing juvenile eels or bait fish after finishing a period of fasting.
The seal has since continued his journey up the North Esk, and could haul itself again further up the river.
DPIPWE Marine Conservation Program wildlife biologist Sam Thalmann said it was not uncommon for fur seals to move into larger estuaries such as the Tamar and Derwent river systems.
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"The seal is most likely moving away from the Bass Strait breeding colonies. The period of males interacting at the colonies has finished," he said.
"They have been fasting, so they would be keen to find a good prey base.
"Seals in freshwater and in the upper reaches are fine. They can very often spend a number of weeks there with no detriment."
A number of dog walkers spotted the seal this morning and dogs approached, but the seal appeared content provided they did not get too close.
Mr Thalmann said the seal was not dangerous to humans or animals if left alone.
"A seal such as this one forraging has no territorial behaviour. They need space to undertake their forraging and space to be avoided when they haul out.
"If anyone comes across a seal, maintain a minimum of 20 metres and do not get between the seal and the water. The seal is going to temporarily resident in that area and will likely move out very quickly."
The section of the North Esk where the seal was spotted has EPA signs warning of PFAS contamination and that people must avoid consuming fish.
Mr Thalmann said the seal was likely only going to be in the waters for a short period.
Anyone who spots a seal in a river is urged to contact Tasmania Parks and Wildlife Whale Hotline on 0427 942 537 (0427 WHALES).