A shark strike has caused a setback to Rena salvage operations after container-seeking sonar equipment was damaged in an attack.
Braemar Howells, the container and debris recovery team, said its magnetometer had been damaged while it was being trawled behind their boat in the search for sunken containers.
Braemar's New Zealand operations manager Neil Lloyd said the equipment was worse for wear after its encounter with the shark.
"The sonar is trawled behind the vessel. It suddenly stopped working and we've brought it in.
"It's impacted on to the surface of the magnetometer and there's some damage to the cable. Apparently it happens quite a lot," he said.
The delicate sonar equipment inside the trawling capsule wasn't damaged and Mr Lloyd hoped to have the apparatus back out in the water today.
"It wasn't like a crushed can or anything. These things are quite robust. The sonar vessel is being repaired now. We're hoping to have it back operational by tomorrow," he said yesterday.
The shark strike wasn't immediately noticed at the time it occurred, so the breed of predator wasn't known.
"We didn't see anything. We bring it to the surface, and there it is," Mr Lloyd said.
The most common type of shark in Bay of Plenty waters is the bronze whaler, often mistaken for the thresher.
Department of Conservation marine scientist Clinton Duffy said sharks commonly found inshore in Bay of Plenty waters were the school shark, rig (also known as gummy shark or spotted dogfish), bronze whaler, juvenile smooth hammerheads and juvenile thresher sharks.
Offshore, blue and mako sharks were commonly encountered species, he said.
"Bronze whalers can be common on offshore reefs and there are reports of what sound like large dusky sharks [usually misidentified as bronze whalers] from Mayor Island and Volkner Rocks most summers. "
Braemar Howells' media liaison Grant Dyson said he had been told by Braemar's operations manager Neil Lloyd that divers had seen hammerhead sharks - highly effective predators that are about 4m long - around Rena.
"All those sharks (species) are out there, it could have been any of them. We're all speculating here. Neil did say to me that divers had sighted hammerheads," he said.
While the retrieval of sunken containers has momentarily stalled, container recovery from Rena's decks has finally gotten back underway after an idle four days.
The repaired crane on the Smit Borneo, combined with some calmer weather, saw a total of 17 containers removed from the beleaguered ship over the weekend.
Nine containers were retrieved on Saturday and eight more on Sunday. The total removed from Rena is now 227.
One more container, which fell off Rena on Sunday, has already been recovered. The container, filled with meat products, followed the two which were washed off the deck on Thursday and brings the number of containers washed overboard from Rena to 89.
Meanwhile, 23 little blue penguins from the western side of Motiti Island were released yesterday. The penguins, from Sandy Bay, north of Panaturi Point, were released by boat. This means only 43 little blue penguins and one dotterel remain at the Te Maunga oiled wildlife facility.
Four new oiled penguins were picked up over the weekend: two from Motiti Island and two from Mount Maunganui.