The gruesome discovery was made by people visiting Lake Wendouree in Ballarat in Victoria's Central Highlands, who raised the alarm with staff at nearby Pipers By The Lake.

Head chef, Matt Milner, located the adult swan's headless body in an area popular with children and families about 8am.

Mr Milner picked up the swan and placed it in a box away from the public eye before searching the area for its head and neck. It was nowhere to be found.

Wildlife rescuer, Sharon Hinchliffe, attended and transported the swan to a veterinarian. She described it as "traumatic".

"It is horrendous that this has happened and that it was likely caused by a human," she said.

With school holidays underway, Mr Milner said there were lots of children and families enjoying their Saturday morning at the lake, making the incident even more "concerning".

He does not believe much time had passed between the attack and when he found the swan.

"The fact there is someone or people out there carrying around a knife or blade of some description to do this is pretty concerning," he said.

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Mr Milner described the injury as a "clean cut" and was not the type of wound that would be the result of an animal attack.

Grampians Manager of Regulatory Operations, Brian Hamer, said a veterinarian examination revealed the base of the swan's neck was sliced through with a sharp object - likely caused by a human.

"The Conservation Regulator takes all matters of wildlife cruelty seriously," he said

Mr Hamer appealed to the community to report any information about the incident.

It is understood there have been similarly disturbing incidents involving swans at the lake in recent years.

All wildlife in Victoria is protected under the Wildlife Act 1975 and killing, harassing or disturbing wildlife can attract a penalty of up to $8000 and an additional fine of more than $800 per animal.

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Ms Hinchliffe expressed that she wished more could be done to protect wildlife.

"Our wildlife goes through so much around the lake-being hit by cars, let alone these incidents. I wish more would be done to protect wildlife."

The Courier's Nature Notes columnist, Roger Thomas, described the incident as "distressing".

"It is a senseless act," Mr Thomas told The Courier. "It's just shocking. It's hard to believe people would behave like that."

Constantly in contact with humans, Mr Thomas said the black swans at the lake were not as timid as others elsewhere.

"They could be taken advantage of because of that by someone who wanted to harm them because they would expect to be greeted in a reasonable manner."

Black swans form a pair when they mature and mate for life, raising a brood each season.

Adult swans are currently splitting into pairs, finding nests, mating and defending their territories.

If the swan was mature enough to have found a mate, it means their mate would be lost without them and it would be difficult for them to find another.

Each year Mr Thomas conducts a count of the bird numbers at Lake Wendouree, which he just so happened to complete on Tuesday.

In doing so, he found almost 40 different species of birds: 20 non water bird species and 19 water bird species.

During the endeavour, which took him about three-hours, he counted 88 black swans.

He said this figure was largely consistent with the number he counted last summer. He will further explore the numbers in his column in Friday's paper.

Mr Thomas said most people appreciated the birdlife at the lake and would be distressed by the news.

"The lake's swans are a treasured part of Ballarat's community, giving pleasure to so many citizens from toddlers to seniors," Mr Thomas said.

"It's very disappointing that anyone would deliberately hurt them."

He urged anyone who witnessed cruelty against wildlife to report it to authorities for investigation.

Anyone with information about this incident or other cases of wildlife crime should contact Crime Stoppers Victoria on 1800 333 000 or file a report online at: www.crimestoppersvic.com.au/report-a-crime

Anyone who comes across injured wildlife is urged to contact Wildlife Victoria on 8400 7300.