It was hoped the whale, spotted off the coast of St Clair and St Kilda, Dunedin, at the weekend, would stay in the area so a whale entanglement rescue team from Kaikoura could attempt to disentangle it.
St Clair photographer Mark Stevenson alerted the Department of Conservation to the whale's plight at the weekend.
Using a large camera lens, he was able to see the line around the whale before it disappeared off White Island.
"It was like it was trying to flick it off and on closer inspection I could it was around its whole body."
Doc Coastal Otago acting manager David Agnew said he had notified the team at Kaikoura which was experienced in dealing with whale entanglements but they needed to find out where the whale was.
"If any fishing boats are out there or people living along the coast who might see it, they should give us a call."
Doc Kaikoura ranger Mike Morrissey said the whale could survive for months with the rope tied around it, as it was migrating through, but with it wound around the tail or if it was through its mouth it could die.
A team of Doc and whale experts would travel down with their specialised equipment to try to disentangle the whale, a process which could take an entire day, Mr Morrissey said.
"We're hoping it will stay around for a few days. Southern rights are prone to do so."
It would be the first time the team had tried to disentangle a southern right whale, he said.
Advice from Australia and the United States, where they dealt with the whales more often, was to "be very wary".
Anyone who sees the whale is asked to call 0800 362-468
