Washington used 1 pneumatic fish cannon to solve salmon passage past a 60m hydroelectric dam; the result transformed blocked rivers into thriving spawning grounds

Washington used 1 pneumatic fish cannon to solve salmon passage past a 60m hydroelectric dam and create another way for migrating fish to reach upstream waters. The technology is known as the Whooshh PassagePortal and is also called the Salmon Cannon. Developed by Bellevue-based Whooshh Innovations, the system uses a flexible tube, air pressure and water mist to move fish over large barriers. It was used in efforts involving dams such as the Cle Elum Dam and Roza Dam. The approach was designed to address a problem created when large dams blocked salmon from reaching areas where they once migrated, spawned and completed their life cycle.

How the Salmon Cannon moves fish over dams?

The system does not work like a conventional cannon. The name comes from the way the fish are rapidly transported through a tube. The process begins when migrating fish enter a short artificial chute. The chute floats and resembles a small waterfall. Fish are attracted to moving water and enter the system voluntarily.


Once a fish reaches the portal, a machine-vision scanner photographs it. The system can take as many as 18 images in less than one second. An artificial intelligence system then assesses information such as the fish's size, weight and species.

The system can sort fish according to the information collected. Native salmon can be directed toward the appropriate tube size, while invasive fish can be blocked or separated.

The salmon then enters a flexible tube with a fabric lining. The tube forms a light seal around the fish. A pressure difference is created around the fish, with gentle air pressure behind it and a vacuum effect in front.

Water is continuously misted inside the tube. This provides lubrication and helps the fish breathe during the journey. It also helps reduce the chance of scales being lost.

The fish can travel through the tube at speeds of up to 22 mph, or about 35 km/h. A journey over a 60-meter dam can take about 20 to 60 seconds. The fish then exits into the lake or reservoir above the barrier.

Washington used 1 pneumatic fish cannon to solve salmon passage past a 60m hydroelectric dam

Large dams can create a major obstacle for salmon that need to move upstream. The Cle Elum Dam in Washington is about 60 meters high, or roughly 200 feet. The Roza Dam is another structure associated with efforts to address fish passage.

The problem became more serious because some dams were built more than a century ago without fish passage systems that could support salmon migration. As a result, salmon lost access to parts of their upper watersheds.

The pneumatic fish cannon offered another way to move fish around these barriers. Instead of requiring salmon to fight strong currents for long periods, the system transports them through the tube in less than a minute.

Why fish ladders and truck transport can be difficult?

Fish ladders have been used for decades to help migrating fish move around dams. They normally contain a series of pools or steps that allow fish to move upward. At large dams, however, fish may have to spend significant time moving through strong currents. The effort can leave fish exhausted. They may also face injury or predation during the journey.

Another method is known as trap-and-haul. Workers capture fish manually and place them in oxygenated trucks or barges. The fish are then transported around the dam. This method requires people to handle the fish directly. The process can create stress and can also increase concerns about disease transmission and mortality. The Salmon Cannon was developed as a way to reduce some of these handling requirements while providing a rapid route around large barriers.

More salmon can be transported during migration

The system is designed to handle a large number of fish during migration periods. A single system can transport up to 60 fish per minute. At that rate, the stated capacity can reach as many as 86,400 fish in a day. This matters during periods when large numbers of salmon are moving upstream within a limited migration window.

Rapid transport also means the fish spend less time fighting currents around a dam. A journey that could otherwise take hours can be reduced to a trip through the tube lasting less than a minute. This can help salmon conserve energy before they reach their spawning areas. Salmon need energy to continue their upstream journey, prepare spawning areas and reproduce.

How the technology can support spawning grounds?

The main purpose of moving salmon upstream is not simply to get them past a dam. The larger goal is to restore access to habitat where the fish can spawn. Salmon use upper watersheds for spawning. When dams prevent access to those areas, the available spawning habitat is reduced.

Restoring passage can therefore allow fish to reach areas that have been inaccessible for decades. Salmon can then use those waters to build nests, known as redds, and lay eggs.

The technology has been used as part of efforts to repopulate previously blocked spawning areas in Washington. The broader objective is to restore salmon runs and return a species that plays an important role in Pacific Northwest ecosystems.

The cost difference between permanent infrastructure and a mobile system

The cost of fish passage is another factor in decisions around large dams. A permanent engineered fish-passage structure can cost more than $60 million. Such projects can require major construction and infrastructure around an existing dam.

The mobile and floating Whooshh system has been described as costing about $10 million. That is roughly 16% of the stated cost of a $60 million traditional project. The difference can make fish restoration possible at locations where a large permanent structure would be difficult to finance or construct.

What studies found about fish health?

The system has also been examined for possible effects on fish health. Studies conducted by organizations including the Pacific Northwest National Laboratory looked at whether transportation through the system caused problems for the fish.

The findings cited for the technology reported no adverse health effects, scale loss or behavioral issues associated with the passage system. These findings supported the use of the technology as another method for transporting salmon around large barriers.

What the Salmon Cannon means for blocked rivers?

The technology represents a change in how fish passage can be approached at large dams. Traditional methods remain part of fish restoration programs, but pneumatic fish transport provides another option. For rivers blocked by high dams, the system can move fish around the structure without requiring them to climb a long fish ladder or undergo conventional truck transport.

The approach also connects engineering with habitat restoration. Moving salmon upstream is only one part of the process. The fish also need suitable water and spawning habitat once they pass the dam. In Washington, efforts around structures such as the Cle Elum Dam and Roza Dam have focused on restoring access to upstream areas. The Salmon Cannon became one tool in that work.

The technology shows how a flexible tube, machine vision, artificial intelligence, controlled air pressure and water mist can be combined to address a fish passage problem. For salmon, the result is a faster route around a major barrier. For restoration programs, it provides a way to reconnect fish with upstream waters that were cut off by dams.