Whitehorse Rapids Fishway

The Longest Swim for the Salmon

Whitehorse, Yukon, Canada

August 24th, 2002

Having arrived in Whitehorse, the Capital of the Yukon Territory, it was time to find something interesting to talk about. One of our outings was to a local landmark, known as the Whitehorse Rapids Fishway. As a background to this, we found out that the Chinook Salmon spawning in the upper Yukon River system undertake one of the longest salmon migrations in the world. They travel almost 1,875 miles against the Yukon River current, fighting rapids and avoiding capture by humans and natural predators. They do not feed during their migration and rely solely on their body fats for energy. Once home, Chinook uphold their legacy and spawn a new generation of salmon then die. The value of salmon being accepted, the comforts of man still caused the creation of a large hydroelectric dam on the Yukon River, in the middle of the City. A great boom to the need for power, it shut down the access to the upper lake region to fish swimming to their ancestral spawning streams. In the mid 1950s, the Yukon Energy Corp., began building this large dam. The salmon were of great concern and much planning went into a solution to get the salmon around the severe turbulence of the water coming over the spillway. Just below the power dam, a barrier dam was constructed across the river. This is a low concrete structure that spans the river, preventing fish from swimming up into the turbulent water below the spillway. The concrete wall angles upstream to direct fish to the downstream entrance of the fishway. The entry at the bottom of the fish ladder offers a good resting place. Water flow in the fishway can be adjusted by valves in the lower ladder to attract the fish into the fishway. The ladder is built in a series of steps. It is approximately 366 meters long and rises over 15 meters. Each step has a vertical baffle that the fish can jump over or they can swim through a submerged opening. The flow of water through each section creates a series of eddies, allowing the fish to rest between each step, while providing enough flow to encourage the fish to continue swimming. Each eddy spins in a different direction from the one below and above. About halfway along the ladder, the fish enter a holding area through a gate at the downstream end. At this point you can see the fish through the observation window in the interpretation building. When the salmon enter, the holding tank gates on both the upstream and downstream sides are closed temporarily while staff observe and record the size, sex and condition of the fish. Also at this time some Chinook salmon are collected for the brood stock program at the Whitehorse Rapids Fish hatchery. To determine how many salmon return to Canadian waters each year, salmon are also captured in three fish-wheels located on the Yukon River approximately 10 kilometers upstream of the Yukon-Alaska border. These live salmon are tagged with long orange "spaghetti" tags. When these numbered tags are returned from the various fisheries, the biologists gain insight on salmon migrations and can determine the number of salmon entering Canada each year. Annual runs through the fishway vary from year to year. Chinook salmon returning to the Whitehorse Rapids Fishway represents 2 to 3 percent of the total Chinook return to the Canadian portion of the Yukon River basin. Spawning also occurs in a number of headwater tributaries of the Yukon River. The rate of return for Chinook salmon average 6 adults for every female that successfully spawns. The various fisheries along the length of the Yukon River take their harvest from these returning adults. Approximately 20 percent of the fry (young Salmon) heading back to the ocean are killed as they passed downstream through the power generating turbines or over the spillway at the dam. When passing through Whitehorse, this is a very good place to get a feel for the relation between man and fish, and what is being done to keep the balance, not to mention some very up close observation of some very big fish.

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