For decades, efforts to restore aquatic ecosystems have revolved around one simple idea: let the fish swim. However, as the hydropower and environmental communities know, designing effective fish passage systems is anything but simple.

Kleinschmidt Associates’ thought leadership paper, One Fish, Many Fish, Pink Fish, Silver Fish, takes readers on a journey beneath the surface of this complex issue. It outlines why traditional approaches to fish passage often fall short—and how a deeper understanding of biology, behavior, and system-wide context is helping us get it right.

As hydropower operators, dam owners, regulators, and environmental consultants grapple with the growing pressures of ecological restoration, this paper invites us to step back and reframe how we approach fish passage, from species-specific designs to broader ecosystem strategies.

It’s Not Just About One Fish—It’s About All Fish

One of the central themes of the paper is that fish passage is not a one-species problem. Nor is it a one-solution answer. Fish species vary enormously in size, swimming ability, migration timing, life cycle needs, and behavioral preferences.

The paper dives into how this diversity plays out in the field. Take lampreys, for example. Their suction-based locomotion means that high-velocity fishways designed for salmon are ineffective—or American eels, whose upstream movement resembles climbing more than swimming. Solutions designed around salmonids won’t work for them—and may, in fact, harm them.

Add to this mix regionally significant species, like sturgeon, shad, or even less charismatic but ecologically important forage fish, and the picture becomes clearer: fish passage design must start with the biology.

Engineering Meets Ecology

Kleinschmidt’s team proposes that fish passage should be at the intersection of science, engineering, and design. Unfortunately, projects are often rushed to meet permitting milestones without sufficient consideration of species biology or long-term success.

The paper emphasizes the value of integrating biologists early in the process. When engineers and ecologists work hand in hand, the result is more effective and sustainable. Whether the goal is upstream passage, downstream survival, or complete connectivity, the best solutions emerge from interdisciplinary collaboration.

Nature-like fishways, for instance, mimic natural stream channels and can serve multiple species and life stages. They require more space and careful design but can create multifunctional habitats. By contrast, technical fishways like vertical slot ladders or fish lifts may be better suited for highly engineered sites or particular species. The paper makes it clear that understanding the goals, constraints, and biological context of a site should dictate the approach—not the other way around.

The Evolution of Fish Passage

Fish passage systems have come a long way, but the paper shows we’re still evolving. While salmon ladders may have set the early blueprint, today’s solutions must be more innovative, adaptable, and inclusive of diverse species needs.

Downstream passage has also gained attention. Juvenile fish, especially out-migrating species like salmon smolts or glass eels, face turbine mortality, entrainment, and predation. The design of screens, bypasses, and flow regimes to safely pass these life stages is just as critical—and often overlooked.

In fact, fish passage can’t be limited to structures. The paper highlights the role of operational strategies—such as flow timing, spill regimes, and temporary barriers—in creating dynamic passage opportunities without major infrastructure overhauls. Adaptive management becomes essential here. Monitor, adjust, monitor again. Success is iterative.

The Policy Puzzle

Navigating the regulatory landscape around fish passage is its own challenge. From FERC relicensing to Endangered Species Act consultations, the paper points out that fish passage is often a pivotal element of hydropower licensing and environmental restoration agreements.

However, rather than viewing regulation as a box to check, Kleinschmidt advocates seeing it as a catalyst for innovation. Collaborative partnerships among dam owners, agencies, tribes, NGOs, and scientists are critical to designing workable, science-based, and cost-effective passage solutions.

The paper showcases several case studies of collaborative fish passage efforts that not only met regulatory requirements but also exceeded ecological expectations—often while building public trust and enhancing long-term project viability.

Design for the Whole Watershed

One of the more progressive statements in the paper is this: effective fish passage isn’t about a single dam—it’s about the entire system. Kleinschmidt encourages viewing fish movement through a watershed-scale lens. A great fish ladder at one site won’t help if downstream barriers block the next leg of the journey, if water quality in between is degraded, or if seasonal flows don’t align with migration cues.

Integrated watershed planning, habitat assessments, and cumulative impact evaluations are all part of this broader approach. The industry is heading toward comprehensive, data-driven, and landscape-oriented strategies that prioritize connectivity.

The Future of Fish Passage: More Than Just Passage

Perhaps most powerfully, the paper closes by calling for a reimagining of what fish passage means. Not simply as a means of allowing fish to pass—but as an opportunity to restore entire ecosystems, support biodiversity, and realign human infrastructure with natural processes.

That’s a tall order. But with decades of field data, advanced modeling tools, and a growing body of biological knowledge, we’re better equipped than ever.

Kleinschmidt’s paper doesn’t claim to have all the answers—but it provides a framework for asking the right questions. What species are we designing for? What’s their behavior? Where are the bottlenecks? What solutions are feasible? Who needs to be involved?

Answering those questions requires humility, innovation, and a commitment to working across disciplines and interests.

Why It Matters Now

As climate change disrupts hydrology, species distributions, and habitat conditions, the stakes for effective fish passage have never been higher. Dams once built for a different time are being re-evaluated—not only for their energy output but for their ecological footprint.

The industry’s role is evolving too. Engineers, operators, and consultants are no longer just problem-solvers—they’re stewards of river systems.

If you’re a stakeholder in the hydropower, restoration, or environmental planning sectors, this is not just another technical guide—it’s a call to rethink how we interact with aquatic life and the infrastructure that shapes their world.

Dive Deeper

To explore the full depth of species-specific insights, technical solutions, and design frameworks, access the whitepaper here:

👉 One Fish, Many Fish, Pink Fish, Silver Fish

It’s time to move beyond the fish ladder. Let’s build systems that help ecosystems thrive—one fish, many fish, pink fish, silver fish at a time.