Seal-mounted camera recovered after 3 years on Nova Scotia ocean floor produces hours of video
Halifax scientists have recovered a wealth of research data lost to the ocean floor off Nova Scotia for 3½ years.
The remarkable recovery includes 19 hours of video from a camera attached to a gray seal. The camera was lost in 2018 and dragged in fishing gear this summer.
“I was shocked, absolutely shocked,” said Department of Fisheries and Oceans biologist Damian Lidgard.
Not only did they recover the camera, but it is still working and will be redeployed next month.
Lidgard had attached the device to a young male gray seal on Sable Island on December 31, 2017.
He hoped to see the male disembark where he could easily retrieve the camera and another built-in sensor that records dive depth, temperature, acceleration and other data.
“Essentially, for the next three or four weeks, every day I searched Sable for this male and never found him,” Lidgard said.
The device probably fell out of the seal when it moulted in the spring.
Where are they going? What are they eating?
The $10,000 camera was deployed as part of an Ocean Tracking Network research project to track the movements of gray seals at the giant colony on Sable Island. Scientists want to know where they go and what they eat.
The instrument was believed to be lost until this summer when it was retrieved from the ocean floor by the Arctic Endurance, a Clearwater Seafoods vessel fishing for surf clams on Banquereau Bank.
The Clearwater clam team made the discovery
A crew member on board contacted the Australian manufacturer, Customized Animal Tracking Solutions (CATS).
The company contacted Lidgard to ask if this was part of their research project. A crew member from Arctic Endurance brought him ashore and handed him over to Lidgard.
“There were a few marks on the camera, but overall it was in very good condition,” he said. “My first impression was that he survived remarkably well, considering he was at the bottom of the sea.
The camera was returned to Australia where the company downloaded the data from its memory storage card.
“I wasn’t really hoping there was anything on it, but I had a full set of data,” Lidgard said, noting there were 59 20-minute videos on the card. of storage.
Lidgard received the video a few weeks ago and are still going through it.
One of the high-res videos shows the male seal diving, feeding and chasing females on the surface in January 2018. Exxon’s Sable natural gas production platform is visible in the distance.
Did you know that seals sleep at the bottom of the ocean?
Video is still being verified for one of the most notable behaviors revealed by other gray seal cameras off Sable: sleeping on the ocean floor and rolling with the current.
Video provides information not available from other sensors.
“A sleeping seal’s dive profile resembles a U-shape,” Lidgard said. “The seal goes down to the bottom, spends time at the bottom, then comes up to the surface.
“Well, it’s a remarkably similar dive profile to a seal looking for food. So without video you can’t tell if you’re seeing it as feeding or if the seal is sleeping. But now we can rely on this video footage.”
He said a previous video showed a seal sleeping for 16 minutes on the sea floor at a depth of 120 meters. The heart rate slows to a few beats per minute, a nap in deep water on fishing grounds that can be over 100 kilometers from Sable.
Lidgard said researchers in the past interpreted the behavior based on numbers from satellite transmitters and time depth recorders. They looked at how deep the seal had dived and how long had it dived.
“With the video camera, I can sit at my desk and watch this animal at sea, behave, dive deep, feed, hunt females,” he said. “I don’t have to make assumptions about what the seal is doing.”
The camera will be attached to a female seal next month. When she returns to shore to give birth, the camera will be retrieved.
“Less stress. Less anxiety,” Lidgard said.