A School for Atlantic Salmon
Tory Meringer ’25 spent her internship researching Atlantic salmon in Woods Hole through an internship offered by NOAA and Maine Sea Grant
Atlantic salmon—a silvery species also known as the “King of Fish” for its size and strength—was once found in almost all coastal river systems in the northeastern U.S.
Nowadays, because of dams, overfishing, pollution, and warming water temperatures, Atlantic salmon are listed as endangered under the federal Endangered Species Act. The only wild Atlantic salmon left in the country are found in just a few rivers in Maine.
For years, scientists and conservationists have worked to learn more about Atlantic salmon in order to help the species. This past summer, Tory Meringer ’25 joined their ranks.
The environmental science major from Belmont, Mass., completed a paid sea-run fish internship offered by the National Oceanic and Atmospheric Administration and Maine Sea Grant, with some funding assistance through the Environmental Studies Department.
Meringer worked primarily at the NOAA Fisheries Woods Hole Laboratory in Woods Hole, Mass., which is the nation’s oldest marine research station. She gained experience in the field at a place where important marine science research is conducted on an ongoing basis.
“There’s just so much happening there, so many studies that are going on, and so many research areas that I hadn’t even thought about before,” she said. “They’re also awesome in making sure that students get a great experience and actually get to be really involved. You get to feel like you’re really doing science.”
A complex life cycle
Meringer worked with Ruth Haas-Castro, a NOAA research fishery biologist, on a project focused on discovering the age of Atlantic salmon and measuring the scales of the smolts, or young fish.
Salmon have a complex life cycle. It begins in rivers, where they hatch and grow as juveniles for two or three years before migrating to the ocean to feed and mature for a couple more years. They finally head upriver to spawn and begin the cycle anew, generally facing challenges such as waterfalls and fish ladders on their journey.
Scientists have learned that for salmon, size matters. When smaller smolts leave the river for the ocean, they are less likely to survive.
One of the rivers where there is still a population of wild Atlantic salmon is the Narraguagus River in eastern Maine. There’s a historical record of scale samples taken from two- or three-year-old salmon in the river that dates back nearly 30 years. Meringer used those scale samples to determine the age of the fish and how much recent growth it added before heading out on its ocean migration.
“It was cool because I feel like I hit a lot of different parts of the research,” Meringer said. “I got to be part of this historical record.”
Summer of scales
A big part of Meringer’s work involved looking at the scales under a microscope to count growth rings and figure out the fish’s age. There are some similarities with the way trees are dated by counting growth rings, but with the fish, each ring is not equivalent to a year.
Instead, salmon grow quickly in the summer, which translates to wider bands on their scales, and grow more slowly in the winter, with narrower bands. At the end of the winter band, Meringer marked an annulus, or one year. It wasn’t always easy to delineate the bands, but she had plenty of practice while dating 350 or so scale samples, most of which were taken from fish last spring.
She’d pick the impossibly small samples up with forceps and tweezers, put them on a slide, and make sure they hadn’t broken or were too smudged to date. Then she’d take an image of the scales and measure the radius between every ring on the scale as well as the annuli markings.
“It was really cool to actually get to see what they looked like,” she said.
Information gleaned from the scales tells scientists how old the fish are when they leave the river. It also sheds light on something that Haas-Castro is especially interested in: Why do the fish add what’s called compensatory growth just as they are about to leave the river?
“Some people think it’s because the fish are too small, and so they need to bulk up quickly before they leave the river, in order to survive,” Meringer said. “We want to understand how big that growth is and why it’s happening.”
Her summer research project provided an important contribution to the 25-year time series of smolt monitoring on the Narraguagus River, according to Haas-Castro, who has been mentoring college students as summer interns for a quarter of a century.
“Tory definitely stands out among my mentees as someone with ambition,” Haas-Castro said. “She came with genuine interest in learning and experiencing as much about endangered Atlantic salmon and their ecosystem as she could in her short time with us.”
Adding to the puzzle
Meringer’s work at Woods Hole was one piece of a larger puzzle. Researchers are examining how changing water temperatures and water-flow levels may be affecting the age and size of the fish as they leave the river, and what impact that will have on the survival of the species.
Scientists are noticing that more fish seem to be leaving the river and starting the migration to the ocean when they’re three years old, not two years old. This may be to better avoid predators and safely make their long, arduous journey to the waters off Newfoundland, Labrador, and Greenland, Meringer said.
“It might mean that they’re under too much stress in the river and aren’t growing enough, and then have to wait around another year before they can leave,” she said. “It’s cool that, evolutionarily, they know they have to get bigger.”
Through the internship, Meringer did get to step away from the microscope to come to Maine, where she visited one of the fish hatcheries helping to keep the last remaining natural populations of Atlantic salmon alive. She also went on a field trip with the Maine Department of Marine Resources to the Sandy River in western Maine to learn about the initiatives to bury or “plant” salmon eggs in streambeds so that the fish will have the best chance of hatching and surviving.
Haas-Castro, her mentor, said that Meringer took advantage of the opportunities for learning.
“Tory came to us with a great science background but no real experience or coursework regarding fish or fisheries,” the research scientist said. “She left only a couple of months later with proficient knowledge on the plight of endangered Atlantic salmon and what NOAA Fisheries, Maine Sea Grant, the Maine Department of Marine Resources, and other scientists are doing to restore Atlantic salmon to sustainable population levels.”
For the student, her summer experience gave her more insights into Atlantic salmon, a species discussed in some of the policy-oriented courses she has taken at the College.
“But I didn’t think I quite grasped how endangered they were until this summer,” she said. “Some of these rivers have really minimal amounts of adults coming back, and so they heavily rely on eggplanting from hatchery fish to keep the population sustained.”
The internship with NOAA and Sea Grant, along with a previous summer Undergraduate Research Experience at the Bigelow Laboratory for Ocean Sciences in East Boothbay, confirmed that she wants to keep on doing science. After graduation, she’s hoping to do fieldwork for a year or two before starting graduate school.
“There’s so much research to be done, and so many different areas to look into,” Meringer said. “There’s a lot of different routes that I can take right now, which is exciting.”
