A seal had hoped to return to the salmon farm it had been evicted from several times but was foiled by authorities.

A seal's insatiable hunger for fresh-farmed salmon has ended in an epic 130-kilometre trek around the South Island.

John Lynn discovered the small fur seal while walking his dog in the North Canterbury suburb of Ohoka on Thursday morning.

It appeared to be exhausted, snoozing on the bank of a stream 11km from the coast.

When Lynn called the Department of Conservation, local ranger Anita Spencer sensed an old foe. She had a feeling she knew this particular seal.

Three weeks prior, she had removed it from a nearby salmon farm, when the manager found it sitting outside the sliding doors on his deck.

She took it to the river, shaving a small patch of fur from its head so it could be identified.

It returned to the salmon farm three days later and was quickly evicted.

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The rangers decided to release it at Birdling's Flat about 75 kilometres away, hoping it would not return.

"We joked about how long it would take to get around the peninsula," Spencer said.

"It has to pass all these seal colonies, two marine reserves . . . I really didn't expect to see it again."

But it came back, fatter and healthier than before. Over three weeks, it had swum around Banks Peninsula, along the east coast and back up the Kaiapoi river, a journey of around 130 kilometres.

The shaved patch confirmed it was the same seal.

It had likely hoped for a triumphant return to the salmon farm but missed its turn-off, ending up further inland at Ohoka.

Spencer, again, foiled the seal's plans – this time she took it to Taumutu, about 100 kilometres away, hoping the extra distance would be a deterrent.

"It's got another 30km to swim this time but it seems quite determined . . . we've got at least another three or four weeks before it comes back again.

"Seals just do these things and we've just got to enjoy them."