The Department of Environment, Land, Water and Planning advised the seal at the Port Fairy boat ramp was put down on Monday.

The operation involved staff from the Department of Environment, Land, Water and Planning (DELWP), Department of Jobs, Precincts and Regions (DJPR), Victoria Police and Moyne Shire.

DELWP's Mark Breguet said forest and wildlife officers had been monitoring the seal and sought specialist advice from veterinarians before the seal was euthanised.

"All management options, including translocating the seal, were considered, however based on our observations and reports from the public, the seal's aggressive and unpredictable behaviour posed too great a risk to the community," Mr Breguet said.

"The seal was also suffering from a jaw deformity, which we believe influenced its increasing reliance on humans for food.

"Translocating the seal was not considered suitable as it would have struggled to survive in the wild with the jaw deformity and its food source removed."

Mr Breguet said euthanising the seal was considered the only viable option to ensure public safety.

"The seal had been at the boat ramp for around four months and became increasingly dependent on fish scraps being discarded by anglers," he said.

"This dependency led to it becoming more aggressive as it sought food from humans.

"Unfortunately, a member of the public was bitten by the seal in late March, which prompted investigations to manage the seal.

"It's a sad outcome, however the decision was based on community safety and concerns for the seal's capacity to survive in the wild.

"This situation highlights how quickly a wild animal can become dependent on humans for food to the point where they show aggression."

It is illegal to feed seals. Under the Wildlife (Marine Mammals) Regulations 2009, the offence for feeding a seal carries a $242 on the spot fine, and a maximum fine of up to $3,223.80.

Minimum distances apply around seals. Remain at least 30 metres clear of seals on land, or five metres from seals on boat ramps or piers.

Dogs are not permitted within 50 metres of a seal on land and should be kept on a lead.