The concept of a fishway is older than most people realize. According to Wikipedia, fish passes have been documented as far back as the 17th century in France, where shallow notched boards were placed in weirs to let salmon through. The design has evolved significantly since then, but the fundamental principle remained the same for centuries: create a water channel that fish can swim through past an obstacle.

That logic is now being challenged by technology that approaches the problem from a completely different angle. Instead of routing water to guide fish, modern pneumatic systems move fish through air-pressurized tubes. The results, in terms of passage speed, selectivity, and stress on fish, are meaningfully better in most deployment scenarios.

What Is the ASPFishway and How Does It Fit the Modern Fishway Model?

Whooshh's ASPFishway is the entry component of the PassagePortal systems. It serves the same function a traditional fishway does at the entry point of a ladder: attracting fish and providing a path inside the passage structure. What's different is the design logic.

The ASPFishway is adjustable in angle, depth, and flow volume. It creates an attraction flow using water drawn from the tailrace rather than the forebay, which is important because tailrace water is cooler and more naturally aligned with the migration path. Fish locate it without artificial guidance structures. They swim volitionally, which means the entry decision belongs to the fish and not to a net or handling crew.

The adjustability matters for seasonal variation. Water levels change across a migration season. A fishway that can only operate within a fixed flow band will underperform at the tail end of migration when river levels drop. The ASPFishway's modular aluminum construction allows in-field adjustment without engineering intervention.

What Role Does the Fish Tube Play in This System?

Once a fish enters the ASPFishway and passes through the FishL imaging zone, the fish tube takes over. The MigratorTube, Whooshh's proprietary flexible transport tube, is the mechanism that physically moves fish from the passage entry to their destination upstream or downstream of the barrier.

The tube design is the product of five-plus years of materials research and field testing. The tube itself is a continuous flexible extrusion with embedded misting ports that keep the interior wetted throughout the fish's journey. The misting serves two functions: it keeps the fish hydrated during air transit, and it reduces friction, allowing the fish to slide smoothly at 25 feet per second without the tube walls abrading their scales.

Why Does Entry Design Affect the Whole Passage Outcome?

There's a temptation to focus fishway assessment entirely on throughput numbers. How many fish per hour? How fast do they move? Those are relevant questions, but passage efficiency begins before a fish enters the system. A poorly positioned fishway that doesn't attract fish to its entry point has a throughput of zero regardless of how capable its internal mechanics are.

Whooshh designs the ASPFishway to be positioned within the natural attraction flow, the area where upstream migrants naturally congregate. This reduces entry delay, which is one of the key welfare metrics for migrating fish. Energy reserves not wasted holding below a poorly positioned entry point are reserves available for the migration ahead.

Here's what differentiates the Whooshh fishway approach from conventional designs:

• Adjustable attraction flow using tailrace water, matching natural migration cues

• Volitional entry with no handling, netting, or external motivation required

• Modular aluminum construction for field adjustment across seasonal water level changes

• Integrated with FishL Recognition for real-time species identification and selective routing

• Compatible with both the PassagePortal floating systems and land-based configurations

What Does This Mean for Operators Evaluating Fishway Options?

The TUber mobile fish transport system extends this platform logic to operations that don't need a permanent installation. For river managers or hatchery operators who need temporary or seasonal fish movement capability, the TUber combines the same air-pressure transport mechanics with a mobile trailer setup deployable by a small crew.

The shift from water-based fishway to air-pressure transport tube represents a genuine design discontinuity, not an incremental improvement. For any operator currently specifying new passage infrastructure, or reviewing the performance of existing structures, understanding what the modern fishway architecture makes possible is a necessary part of that evaluation.