'Big and powerful' shark attack left ocean glider adrift off Nova Scotia for days

An autonomous ocean glider was disabled by a shark attack Sunday night near Sable Island, abruptly ending a scientific mission and putting the vehicle out of service for months.

The wave glider was 200 kilometres off the coast of Nova Scotia listening for tagged halibut.

"We lost communication with the rudder module, so we were no longer able to steer the glider, so it was drifting freely," said Richard Davis, manager of the glider group at Dalhousie University. "But we still had communication with it. We knew where it was all the time."

An emergency 76-hour effort was undertaken to retrieve the glider which revealed teeth marks and punctures all over what is called the "thrudder," a combination thruster and rudder.

A close-up of the rudder and thruster shows the damage incurred after a Sunday shark attack. (Paul Poirier/CBC) The glider was returned to a Dalhousie facility on the Dartmouth waterfront. Fred Whoriskey of the Ocean Tracking Network examined the bite marks and swabbed the damaged area for environmental DNA traces in an attempt to "figure out who the culprit is of this particular attack on this innocent autonomous vehicle."

"It must have been a pretty big and powerful shark because it managed to penetrate three millimetres or more with teeth marks into the aluminum base of what's solid aluminum," said Whoriskey.

Identifying the culprit He said the shape of the bite marks rules out a porbeagle. He thinks it was most likely a mako or great white shark because they're regularly in the area.

Whoriskey said it might even be a tiger shark, which is cold-blooded. He said they tend to come up later in the summer when the water has warmed up.

It's unclear what prompted the attack. Noise from the propellers or electronic signals may have attracted and irritated the shark. It could have been a taste test to see if the glider was food.

"The third possibility is if you look at the colour of the machine, this is what in the industry they call yum yum yellow," said Whoriskey. "It is a high-contrast thing and can tend to excite an attack under some circumstances."

Fix will cost about $25K The attack has put the glider out of service until a new rudder system can be secured, which will likely cost around $25,000, said Davis.

"It's a pretty big deal," he said. "I don't budget for that. We do have a contingency fund, but it's not small change."

Davis hopes the glider will return to the water this year, but said the COVID-19 pandemic has slowed down getting equipment from suppliers.

Why the glider was in the water The damaged wave glider belongs to Environment and Climate Change Canada and is on long-term loan to Dalhousie University.

It was deployed about three weeks ago near a large underwater canyon known as the Gully as part of a project to monitor the movements of Atlantic halibut tagged by DFO earlier in the year.

It was also measuring meteorological and oceanographic conditions, and sending that data back to shore in real time for use in weather forecasts and climate modelling.

Fred Whoriskey is the executive director of Dalhousie University's Ocean Tracking Network. He's ruled out the culprit as being a porbeagle, but says it might have been a mako, great white or tiger shark. (Paul Poirier/CBC) Davis said he believes there have been more gliders in the Atlantic Ocean this year than ever before, meaning more shark strikes are possible.

"If we do start to see a pickup, we're going to have to find some mediation strategies as to how to reduce this kind of thing, because a valuable mission was truncated ... but what those measures are at this point, I don't know," said Whoriskey.

Who is Hal, and why are we monitoring his butt?

Hal is more than likely an abbreviation for HALIBUT.

Ocean biographers monitor many species of fish like striped bass, cod, haddock, sharks etc.

This particular "Ocean Glider" that got attacked by a shark was monitoring acoustically tagged Halibut.-Tom

We’re gonna need a bigger glider.

A lot bigger glider.

The incident below reminded me this. -Tom

Excerpt from shark research committee-
One of the more intriguing cases of a White Shark attack on a boat occurred on 9 July 1953 off Fourchu, on the southeastern coast of Cape Breton Island, Nova Scotia, Canada.

Commercial fisherman John D. Burns, with companion John MacLeod, set out daily in his dory to harvest lobsters. Many dories dotted the sea in their quest of the prized crustacean, but only Burns' had a white-painted hull.

For nearly a week the white-hulled dory was followed by a large shark after leaving the harbor. Day after day the other fishermen watched in disbelief as the shark stalked Burns and MacLeod's dory from behind, just as an African Lion (Panthera leo) on the savanna might stalk a Thomson's Gazelle (Gazella thomsoni). No sooner would their dory put out to sea than a large dorsal fin would appear astern of the boat.

Then, as the dory sailed alone on July 9, the shark charged, smashing a 20-centimeter hole through the bottom of the boat. Burns and MacLeod were thrown violently into the sea. Tragically, Burns was unable to combat the heavy seas and drowned. MacLeod, however, was rescued hours later, clinging cold and forlorn to the hull of Burns' damaged dory. The shark did not return after its initial - and only - strike against the boat.

After the boat was retrieved, an incriminating tooth fragment was removed from the hole in the dory's hull. Ichthyologist William C. Schroeder, of the Museum of Comparative Zoology at Harvard University, identified this tooth fragment as having been lost by "a White Shark about 12 feet [approximately 4 meters] in length and weighing 1,100 to 1,200 pounds [500 to 550 kilograms]."

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