Helping fish go the distance
Smith College engineering students’ partner with the U.S. Fish and Wildlife Service to improve fish passage technology.
Fish migration is a marathon, not a sprint. As many species journey from the ocean to freshwater rivers, fish are likely to encounter man-made dams along the way.
And passing these hurdles is no small feat. Dams are strenuous obstacles for aquatic life and have caused populations of many migratory fish species to plummet.
During the 2019–2020 academic year, Brett Towler, fish passage engineer for the U.S. Fish and Wildlife Service’s North Atlantic-Appalachian Region, partnered with a team of Smith College students to address migratory species decline by improving fish passage technology. The work served as a capstone project, required for earning an engineering degree.
A brief history of fish passage technology
Fish passage technology was first used on the West Coast in the 1950s, after people saw Pacific salmon leaping up rivers. Engineers realized they could exploit this behavior to promote successful migration of these fish.
The designs worked so well that engineers on the East Coast built the same passages, but they were unsuccessful. Engineers later realized what they had failed to consider: East and West coast fish behave differently. West Coast fish have higher energy, while their eastern counterparts are taxed energetically when migrating through designs that require them to jump to the surface.
“Our fish frankly just don’t leap,” Towler said. “They have different behavior. They only have so much gas in the tank, and they’re going to go up as far as they can before they run out of gas.”
Migratory fish have a biological clock that tells them when it’s time to migrate. As soon as they run out of gas, the fish spawn, even if they haven’t reached the right geographical location in the river. This decreases breeding grounds by hundreds of miles.
American shad — A unique challenge
The students designed a passage for American shad. Prior to the construction of man-made dams in rivers, this species populated the entire East Coast. Their historic range went as far north as Newfoundland and stretched south to Florida and west to Minnesota. Without fish passages, shad populations decreased, and this historic range was difficult to maintain.
Compared to their migratory counterparts, shad have a difficult time passing dams. Known as weak swimmers, they are also sensitive to noise and light and particular about water temperature and flow velocity.
But the biggest technical challenge for the team was shad’s aversion to openings — like underwater fish passages. After extensive literary review, the team realized the designs they were reading about were not going to cut it; they would have to create an original fish passage design from scratch.
“This motivated us to design something that had never been designed before, so we had that creative freedom,” said student Jody Huang.
Merging engineering and biology
All members of the team had engineering experience, but their background in wildlife biology was limited. This pushed them to acquire extensive on-the-job knowledge of fish behavior. The interdisciplinary nature of the project was a motivational force.
“We didn’t know anything about fish behavior,” said student Francesca Giardine. “That was something we actually really got into learning about.”
Chris Conley, a retired civil engineering educator, was recruited as acting advisor to the students. Prior to this experience, Conley had not given much thought to the impact dams have on migratory fish.
“I wasn’t aware of how poorly we’re servicing the fish community on this planet of ours,” Conley said. “We’ve blocked their natural way of procreating and are not succeeding very well at helping them get around barriers that we put up.”
The U.S. Geological Survey was a partner to the project. Among those involved was Kevin Mulligan, a hydraulic engineer from the Conte Anadromous Fish Research Center in Turner Falls, Massachusetts. He assisted with passage entrance design and water flow calculations.
There were additional partners from the Service as well. Julianne Rosset of the New England Field Office in Concord, New Hampshire, and Bryan Soikowski of the North Atlantic-Appalachian Regional Office in Hadley, Massachusetts, provided technical support and guidance to the team.
The team developed a numerical model for a vertical slot design as a control structure. This allows for a variety of water flow speeds for a variety of fish species; rates are faster near the surface and slower near the bottom of the passage. American shad prefer slower water flow, but the team recognized a successful fish passage cannot just pass one species.
“While we focused on American shad, we don’t want to preclude other species from passing through,” Giardine said.
Students with passion for environmental conservation
The work was a team effort, but students also accomplished personal milestones and drew inspiration from their own experiences. While Giardine had completed coursework in numerical modeling, the project demanded more expertise. She described her starting level as a two, while the project needed more of a five. Overcoming that learning curve was one of her biggest challenges.
“That was very hard but also probably the most rewarding part of the project,” she said.
Mag Jiang hopes her work on this project will prevent history from repeating itself. A Chinese native, Jiang has seen how man made structures and dams accelerate the decline of once-populous fish species. In the past 20 years, the Chinese paddlefish has disappeared due to overfishing and dam construction.
“Fish passages are an important thing,” she said. “Otherwise, the fish would go extinct.”
Huang was particularly inspired by her time abroad. While studying in Hong Kong, she was exposed to the harsh realities of human pollution and environmental disruption. During her spring break, she traveled to the Philippines, where she saw serious ramifications of human activity on the environment.
“I just remember going towards the rural areas of the Philippines and seeing how there was so much nature, but right across the street you would see infrastructure devastation and plastic everywhere,” she said. “That made me realize how much I want to change something.”
Creating a lasting impact
Conley believes it was valuable for the young engineers to experience such an interdisciplinary project so early in their careers.
“I think we’re getting to the point where most big problems out there are interdisciplinary,” Conley said. “It’s nice to see that come out clearly in a project like this.”
Due to mandatory stay-at-home orders caused by the pandemic, the students did not make it to the physical modeling stage. And yet, the team remain hopeful it will be a success down the road, when the needed facilities are accessible.
“Maybe next year another team will pick it up where this team left off and do the physical experimentation and then refine the numerical models,” Conley said.
And despite the uncertainty this academic year holds, the next group of undergraduate engineers might just push this project across the finish line.
