A dramatic moment fitting a scene from a Melville novel broke the white water of the Cowrie Hole in Newcastle on Friday afternoon as a migrating whale became tangled in a shark drumline just offshore.
A local lifeguard had described the intense moment when the Humpback, which had been travelling up from the south, collided with the drum line suspended between a pair of buoys near the Newcastle Ocean Baths.
"There was an explosion of water, quite violent and aggressive," he said as the tangled leviathan thrashed about, trying to dislodge itself from the line before it seemingly turned on a dime and swam out to sea.
The witness said the buoys were dragged for a short distance before the spooked whale, which appeared to have a calf in tow, was able to dislodge itself and escape unharmed. Moments later, a boat was on the scene to reset the drumlines, which are used as an alert system for sharks swimming off the coast.
The drumlines consist of an anchor, two buoys and a satellite-linked GPS communications unit attached to a hook baited with one sea mullet, according to the Department of Primary Industries, which operates them.
A triggering magnet is attached to the communications unit. When a shark takes the bait and puts pressure on the line, the magnet is released, alerting the boat crew and DPI scientists that there is an animal on the line. Once alerted, the team responds immediately (within 30 minutes) to tag and release the shark or other marine animal.
Drumlines are set every morning, weather dependent, approximately 500 metres offshore at a depth between eight and 15 metres of water. They are collected at the end of each day and are not left overnight.
While the drumlines are designed to be relatively harmless to sharks and any other wildlife and have been shown to be more effective than shark nets, they can mistakenly take in other bycatch.
"The difference with the smart drum line is that the operator is made aware that an animal is caught on the line. From there, it depends on the specific policy, availability of a boat and crew, and sea conditions as to whether the animal gets released. If it takes too long to get to the animal, it is likely to die from stress, suffocation or being eaten by another animal," Marine biologist Alison Kock told the ABC in 2015.
Whales have been a daily sighting off the Newcastle coast as more than 40,000 whales start their epic journey north to warmer waters, but a spate of big surf crashing on the coast over the past week has muddied the waters and the event's witness suspected that the murky conditions could have played a part in Friday's entanglement.
Still, it was the first time in memory that a whale had come afoul of the lines, except for a similar event a few seasons ago, the local lifeguard said.
Rough surf tends to keep the whales further out to sea, he said, but he suspected the conditions caused the whale to catch the drumline around the pectoral fin, leading to a short panic before it ultimately escaped.
A wet weekend in the forecast for much of Newcastle bodes for a chilled and grey few days, with the chance of a thunderstorm on Saturday. Surfline forecasters say a deep Tasman low that has been the source of all the solid south swell this week has wound down, but a shift in the sub-tropical jet stream is moving over the Tasman could see a return of south swells over the weekend.
