Meet Dr. Louise McGarry, Ocean Scientist

Published August 3, 2021

(Photo credit Kathleen Ballard)

Dr. Louise McGarry is an ocean scientist working at Fundy Ocean Research Centre for Energy (FORCE).

What drew you to ocean science?

I moved to Maine with my family when I was 10, spending time camping in the (US) Northeast and Canada. My dad was a sailor, and of the five of us kids, I was the one who spent time with Dad getting the boat ready. I loved being on the water. But as a kid I saw it as recreation…not a job. It wasn’t until I was a junior in college and watching James Bond [in A Spy Who Loved Me] posing as a marine biologist that something sparked. To support his disguise, Bond rattles off all this information about a fish – and in that moment, I knew I wanted to know more about how the ocean worked. The next morning, I ran across campus to find the oceanographers’ offices. I burst in and literally said, “What is it you guys do for a living?” At the end of that year, I spent a week in the marine labs at the University of Maine, learning how a single snapshot of a beach can tell us the story of motion over time – in other words, how beaches migrate. And I learned how core samples of plankton from the sea floor can tell us the temperature of the ocean surface millions of years ago. The first time I looked at those core samples under a microscope, it floored me that there could be that much beauty in such a tiny space.

How did you first get into hydroacoustics?

Before going to grad school in ocean science, I lucked into a job with a dream team of scientists on a boat in the Gulf of Maine, using hydroacoustics to map copepods – the food that Right Whales eat. Copepods are so small that, to find them, you need to use acoustic instruments with really high frequencies – in other words short wavelengths that don’t travel very far. We did the mapping using five uplooking and five downlooking frequencies, so 10 transducers. It’s amazing what we can figure out with sound. We, as humans, are so visually oriented. And vision doesn’t work so well in the ocean because light doesn’t travel very far. We can use this amazing technology to try to answer questions in the ocean that we can’t get at any other way.

When it comes to hydroacoustics and tidal energy, it’s an incredible challenge. Because the water is so turbulent, there’s a tremendous amount of air that gets entrained into the water. This turbulence complicates the interpretation of hydroacoustic data, because it’s very difficult to tell the difference between the sound coming off an air bubble versus the sound coming off the swim bladder of a fish. At a tidal energy site in Maine, we found that the entrained air happens most dramatically at the most important part of the tide cycle – on flood tide – when the fish predators arrived indicating that there were plenty of fish available. It’s a huge challenge, but it’s also what makes this work so interesting: how do we figure this out?

What drew you to tidal energy?

Tidal energy is aimed at the big societal questions. I’m grateful to be playing a role in advancing our efforts to move away from fossil fuels while helping to protect the ecosystem. That, personally, for me is what I’m trying to do. And the fact that I get to do this super geeky work is just fun. I’m using echosounders – basically highly engineered, scientifically calibrated “fish finders” – to help understand the distribution of fish at the FORCE site, and how that changes over the seasons, as different species migrate through the Minas Passage. And from that, help to understand how the presence of the tidal energy devices might affect the fish. Hydroacoustic technology measures time and intensity…which means nothing…until we can turn it into something that’s biologically meaningful. Turning data into something that helps us better understand the world: that’s the part that I really love.


Dr. Louise McGarry specializes in using hydroacoustic techniques to investigate the behaviour and distribution of marine organisms. Louise earned her Ph.D. at Cornell University, where her dissertation focused on the application of hydroacoustic techniques to a unique dataset of concurrently collected oceanic predator-prey data. Louise continued at Cornell University as post-doctoral fellow conducting and analyzing data from the field trials for a variety of ocean acoustic technologies, from high-resolution acoustic telemetry to autonomous hydroacoustic surveys conducted with the newly developed Wave Glider. Louise served as lead acoustic scientist investigating the use of hydroacoustics to quantify the distribution of fish at a tidal energy site in Western Passage, Maine. Most recently Louise has worked with the Pathway Program contributing her hydroacoustic expertise to a machine learning, artificial intelligence project and the automation of a hydroacoustic data analysis and reporting pipeline.