The Yukon River, at about 2000 miles, is one of the world’s longest rivers. It is also one of the most important salmon-breeding rivers. Each year Chinook or King salmon return to spawn in the river’s tributaries such as Michie, Wolf and other creeks near Whitehorse. Once the eggs hatch and the fish grow, they begin an incredible journey.
When juvenile salmon head down the Yukon River in the spring, they face a frightening ordeal. First, many have to pass through Marsh Lake, home to hungry pike. Then in the river itself, grayling, gulls, and more pike feast on the young fish.
These natural hazards make the journey tough enough, but the trip through or around the Whitehorse Hydro dam is daunting. The fish either go through the turbines over the spillway or through the fish ladder. It’s a crapshoot. About 30 percent of the salmon don’t make it. Those that survive the dam face a long and perilous trip down the entire length of the Yukon River.
Until 1959, the Yukon was a free-flowing river from its headwaters to the Bering Sea. The salmon had a relatively easy time swimming upstream and through the Whitehorse Rapids to spawn. The same can be said for the journey back to the sea.
That changed when the Whitehorse dam was completed in 1959. To help the fish reach the spawning creeks, the Whitehorse fishway was built beside the dam. Water from the fishway attracts the fish to the ladder. Once entering the fishway, the salmon jump over partitions which separate the steps that make up the ladder.
About halfway up, the fish enter a large chamber where their size and sex are recorded by fishway staff. A number of salmon are removed for use at the Whitehorse Rapids Fish Hatchery.
The rest are removed from the viewing tank with nets and placed in the upper section of the fishway to complete their climb over the dam. By the time the salmon reach the fishway, they are in pretty rough shape. They have spent three months swimming up the Yukon without eating. The fish are exhausted with just enough energy left to carve nests in the gravel and spawn. Then, they die - but the young will hatch to carry on the historic cycle.
In 1983 and 1984, a salmon transplant program was started at the Whitehorse Fish Hatchery to increase the stocks. Each summer, about thirty percent of the fish swimming through the Whitehorse fish ladder are harvested and taken to the nearby hatchery.
There, eggs are squeezed from the females, while sperm is squeezed from the males.
The eggs are fertilized and hatched artificially in tanks. The following spring the young fish are released into the creeks upstream from Whitehorse. Artificial hatching of salmon eggs is needed to make up for the loss of naturally hatched fry that are killed by the turbines of the power plant as they try to make their way downstream to the sea.
Still, not many salmon hatched or released upstream of the dam ever make it back to their Yukon home after spending their adult lives in the Pacific Ocean. Most will be eaten by other fish or taken at sea by commercial fishers. Some years, only 150 salmon return to the fishway.
The biggest return since the dam was built was in 1996, when nearly 3000 salmon were counted. Biologists speculate that the large return was because the fish managed to escape the deep-sea fishing boats by returning two weeks sooner than expected that year.
But there are always some salmon coming home to their Yukon creeks. So, if you live permanently in Whitehorse, be a tourist. Take a trip to the Whitehorse fish ladder and hatchery and see how man and nature are trying to get along.
A CKRW Yukon Nugget by Les McLaughlin.