Sep. 18, 2012 Anyone with an iPhone is familiar with what an accelerometer does, even if they've never heard of one before. It's the device that tells the screen to turn depending on how the phone is being held.
That same technology is the cornerstone of Dalhousie University student Franziska Broell's research study, which focuses on biological oceanography and sensor development for marine animal tracking. The Ocean Tracking Network is supporting the study.
Broell has an undergraduate degree in applied statistics and marine biology from Victoria University and came to Dalhousie to pursue a PhD in biological oceanography.
When she got here, Chris Taggart, Dalhousie professor and her research supervisor, had a challenge waiting.
"When I first came to Dal, I remember my supervisor gave me a box of circuits and wires and said, 'Here. That's your project.' It took me quite awhile to get into this and to even figure out what an accelerometer was," recalls Broell.
Tracking fish by the tail
She was tasked with developing an accelerometer that could be attached to a fish to record its movements. This device would collect data that would help the team learn more about fish behaviour and growth based on the movement of the tail -- invaluable information for fisheries all around the world. Currently, no one uses a reliable measurement of growth rate in the field.
But first, she needed to learn a thing or two about engineering. Enter: Andre Bezanson, a Dalhousie grad student in biomedical engineering.
The two students met through a mutual friend and ended up talking about Broell's research. Bezanson was drawn to the idea of helping design the accelerometer, even if it meant hours and hours of part-time work on top of the work he's responsible for in his own studies.
"My parents started their careers in oceanography and I grew up living next to the ocean," says Bezanson. "It seemed like an interesting project and a great opportunity to work with the end-user of a product I had personally developed."
Going smaller, more precise
The two students have been refining the technology for over a year now by adapting open source hardware developed by the Arduino electronics community. Over that time, their device has evolved into a much smaller circuit that requires less power to operate while maintaining the quality of the data.
"The first version was a lot larger and it needed a lot more power. Since then I've been able to refine it to eliminate components and simplify the design," says Bezanson.
"We've designed our tags so they can sample up to 500 movements per second," explains Broell as she watches a slow-motion video of a large fish eating a smaller fish. The moment passes so quickly that it's easy to miss. The high-definition video has helped her team show that an accelerometer capable of recording such fast movements is necessary to learn more about feeding behaviours and growth rates.
In January, Broell will bring her fish back to the Aquatron to fit them with the latest version of the accelerometer. By then, the fish will have grown, so she'll re-do all of her previous experiments done with older models of the accelerometers to see what kind of influence the change of size has on the movement of their tails this time around.
"When I can show that the movement relates to the size of the animal, then we can put this into the field," says Broell.
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