Scientists in Halifax have recovered a trove of research data lost on the ocean floor off Nova Scotia for 3½ years.
The remarkable retrieval includes 19 hours of video from a camera attached to a grey seal. The camera was lost in 2018 and dragged up 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, it still works and will be redeployed next month.
Lidgard had attached the device to a young male grey seal on Sable Island on Dec. 31, 2017.
He hoped to see the male come ashore where he could easily recover the camera and another built-in sensor that records dive depth, temperature, acceleration and other data.
“Basically for the next three or four weeks, every single day, I searched Sable looking for that male and never found him,” said Lidgard.
The device likely fell off the seal when it molted in the spring.
Where do they go? What do they eat?
The $10,000 camera was deployed as part of an Ocean Tracking Network research project to follow the movements of grey seals from the giant Sable Island colony. Scientists want to know where they go and what they eat.
The instrument was believed to be lost until this summer when it was scooped up from the ocean floor by the Arctic Endurance, a Clearwater Seafoods vessel fishing for surf clams on Banquereau Bank.
Clearwater surf clam crew made the find
A crew member on board contacted the Australian manufacturer, Customized Animal Tracking Solutions (CATS).
The company contacted Lidgard asking if it was part of his research project. An Arctic Endurance crew member brought it ashore and handed it over to Lidgard.
“There were some marks on the camera, but generally it was in very good shape,” he said. “My first impression was that it’s survived remarkably well, given that it’s been at the bottom of the sea.”
The camera was sent back to Australia where the company downloaded data from its memory storage card.
“I didn’t really have much hope that there’s going to be anything on there, but I had a full set of data,” said Lidgard, noting there were 59 20-minute videos on the storage card.
Lidgard received the video a couple of weeks ago and is still going through it.
One of the high-resolution videos shows the male seal diving, foraging and chasing females on the surface in January 2018. Exxon’s Sable natural gas production platform is visible in the distance.
Did you know seals sleep on the ocean floor?
The video is still being checked for one of the more noteworthy behaviours revealed by other grey seal cams off Sable: sleeping on the ocean floor and rolling with the current.
The video provides insight not available from other sensors.
“The dive profile of a sleeping seal is like a U-shape,” said Lidgard. “The seal goes down to the bottom, spends time at the bottom, then comes up to the surface.
“Well, that is a remarkably similar dive profile to a foraging seal. So without video, you can’t say if you see it as foraging or if the seal is sleeping. But now we can based on this video footage.”
He said a previous video shows a seal sleeping for 16 minutes at the bottom of the sea at a depth of 120 metres. The heart rate slows to a few beats per minute, a deepwater nap on fishing grounds that can be over 100 kilometres from Sable.
Lidgard said researchers in the past interpreted behaviour based on numbers from satellite transmitters and time-depth recorders. They looked at how deep did the seal dive and how long was it diving for.
“With the video camera, I can sit at my desk and actually watch this animal out at sea, behaving, diving deep, foraging, chasing 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 it returns to the shore to give birth, the camera will be retrieved.
“Less stress. Less anxiety,” said Lidgard.
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