Fish are an important natural resource of the Pacific Northwest and the goal of the Bonneville Dam is to keep as many fish alive as possible.
Juvenile fish, or fingerlings, migrating downstream to the ocean can use the spillway as a water slide.
We observe about six sea lions riding the waves searching for a meal.
A second choice is the channel bypass pipe. The third option is made up of rotating guidance screens that divert the young fish around the dam.
The overall survival rate for juvenile fish migrating downstream at BonnevillevDam is 96%. (US Army Corps of Engineers brochure)
For fish traveling upstream fish ladders simulate the waterfalls and pools found in natural streams.
Pools are formed by cross barriers, called weirs, that form steps set in a ramp leading up and around the dam. The weirs have openings along the bottom to allow the fish to swim easily from one stair step to the next. (US Army Corps of Engineers brochure)
The upper portion of this fish way leads to an inclined series of vertical slots and eddy-like pools. (plaque at site)
As fish near the top of the fish way they pass the counting station where workers have been counting and recording the various species moving up the ladder since 1938. (US Army Corps of Engineers brochure)
Migrating fish moving through the fish ladders can be viewed through underwater windows.
Look closely for the black and white shadows I captured.
These long, skinny snakelike creatures attached to the viewing windows are lamprey going up river to spawn between June and October. They struggle upstream thrashing their long bodies against the swift water currents. Using the suction of their oral disc, they naturally attach themselves to a rock to rest. However, as these guys navigate through the fish ladders of the dam, they have to attach themselves to the viewing window to rest. (US Army Corps of Engineers, Portland District)
As we leave the dam and backtrack to I-84, we realize we are actually on Bradford Island and have bisected Robins Island and have a Fish Hatchery to yet explore.
Bonneville is one of the oldest fish hatcheries in Oregon. It opened in 1909.
Visitors are encouraged to pick up a self-guided tour brochure and follow the fish markers painted on the path.
The process begins during September, October, and November. In the spawning room, workers collect adult salmon, count and sort them by species and sex, collect the eggs and sperm, and finally fertilize the eggs. The fertilized eggs then incubate. When the eggs develop into a newly hatched fry, up to 1″ in length, the small fry are placed in an outdoor rearing pond. When a fry becomes a fingerling, a one-year-old, and smolts, turns silver, they are ready to migrate to the ocean. Smolts are released into a pipeline that empties into a creek, then the river, and finally the Pacific Ocean.
Since we are not visiting during salmon season, however, there are sturgeon and trout ponds for the year round enjoyment of visitors like us.
Fish pellets, purchased from vending machines to feed the hungry trout, help maintain the grounds of the Bonneville Fish Hatchery.