The Department of Conservation is urging the public to report sightings of an orca that has been freed from a crayfishing line.

Photo: Unsplash / Tim Cole

Orca Research Trust founder Ingrid Visser says the orca was freed from a crayfishing line east of Waiheke Island at 4.17pm yesterday.

The young male orca had been trapped in the line since Monday.

DOC North Island disentanglement team leader Cat Peters said the line left the orca with some injuries and it was therefore important to report sightings to monitor the mammal.

Dr Peters said the orca was not fitted with a tracker as it had gone through enough trauma with the line.

Throughout the week there were unsuccessful attempts to cut it loose since it first got caught in the line in Northland.

Rescuers feared that the line - which had a buoy attached - could have severed a fin and killed the orca.

Dr Visser said her team used a system called kegging to secure the killer whale.

"Basically you hook onto the original line that's wrapped around the whale and then you attach inflatable buoys to the new keg line that we have on and that means that it also helps keep the whale near the surface.

The rescuers had to wait until the killer whale tired to cut him free using a special hook.

"We have special hooks that allow us to get very close to the flesh - they're very soft, rounded edges on the outside and then on the inside of the hook it's very sharp so we can get it underneath the line and that meants that we don't cut into his flesh."

The rescue mission was being conducted from inflatable boats, as it was believed too dangerous to the orca - a member of the dolphin family - to have people in the water with it as it may cause the orca to dive deeper and possibly drown.

The Department of Conservation's disentanglement team and rangers, Coastguard and police all helped in the rescue.

Dr Peters said they watched the orca swim well and take several breaths after it was freed.

"It's tired from the ordeal and still needs space from the public so it can heal," she said. "The other orca were further away but he was calling, talking to them the whole time, and we're confident they could hear each other.

"This is a fantastic result after five days hard work, and a real team effort."