Helping fish survive: Building walls with fake plant roots

Imagine you’re a fish – darting through the water, dodging predators, searching for food, and trying to find shelter. Now imagine that your only option is a flat concrete wall with nowhere to hide. This is the challenge many fish face in human-made waterways.

Years ago, Keith Van de Riet started wondering: what if we designed seawalls with fish in mind?

Currently a professor at the University of Kansas School of Architecture & Design, Van de Riet has spent more than a decade experimenting with textured seawall panels inspired by mangrove roots.

His latest study – conducted in partnership with scientists from Carleton University in Canada – explored whether freshwater fish, too, prefer these artificial root structures to flat walls.

Nature sparked a design shift

Van de Riet’s interest in redesigning seawalls began while living along a canal in Florida. One day, something he witnessed made him rethink how fish interact with built environments.

“We saw bait fish being chased by predators literally leaping up against the flat side of the seawall, trying to evade them, because they had nowhere else to go,” he said.

Back then, Florida’s coastlines were thick with mangrove roots – natural hiding places for marine life. Those roots became the blueprint for what he would later call “Reef Wall” panels.

Fish preferred textured walls

The Canadian team had followed the professor’s earlier experiments in Florida’s saltwater habitats.

The researchers wanted to know if similar designs could work in freshwater environments – like lakes and seawall-lined canals – using fish commonly found in Canada.

So they built a controlled experiment. In a test tank, they introduced four species one at a time: bluegill, rock bass, yellow perch, and banded killifish.

The fish were given a choice between a flat concrete wall (the control) and four wall panels with increasing levels of texture and complexity.

The results were encouraging. All the Canadian fish liked the variegated walls more than the flat ones.

Habitat tastes varied by fish species

The results also demonstrated that one size doesn’t fit all. Some species were pickier than others. Their preference for the most complex design turned out to be fairly species-specific,

Van de Riet pointed out that bluegill liked – or at least hung out near – the artificial panels the most, followed by banded killifish.

Rock bass and yellow perch showed more versatility, preferring a range of relief depths, according to the researchers.

Better walls for healthier ecosystems

The point of these panels isn’t only to keep smaller fish from being eaten. The more textured the surface, the more nooks and crannies there are for bivalves – like mussels and oysters – to attach.

Those animals can filter water naturally, improving water quality for the entire ecosystem, including the humans living nearby.

The team noted that the research is especially important for places where shorelines are already built up or too heavily trafficked for traditional living shorelines.

Professor Van de Riet said the study is challenging because each species has different behavior. “And they behave differently at different ages. When they’re younger, they’re going to seek refuge, no matter what.”

“As bluegill age, they prefer open spaces because they can see everything around them. So they tried to account for those things based on what they already know about the species.”

The takeaway? Fish respond to structure – but there’s a sweet spot in the design.

Designing for the real world

The work has not stopped. This year, the team is testing the root-inspired panels in an actual lake instead of a lab tank. They’re monitoring how fish respond in more natural, uncontrolled conditions.

“The work includes reaching out to waterfront property owners, doing surveys and trying to figure out what’s the best way to roll out ideas and concepts that would impact how they build on their shorelines,” said Professor Van de Riet.

As more shorelines are paved over with concrete, this research offers a hopeful message: we can still make room for nature. Fish seem to know what they need – we just have to pay attention.

The full study was published in the journal Aquatic Conservation: Marine and Freshwater Ecosystems.

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