Archive for February 9th, 2013

09
Feb
13

Salmon Leaping: How Do They Do That?

Salmon-Waterfall1So in light of my last post about fish above waterfalls or natural barriers: so how do they jump up those waterfalls?

“Good leaps depend on the pool below the falls. The deeper the pool, the better the take-off angle, and the faster the fish can go. Consequently, “the higher the fish can leap,” says education coordinator Jonathan Lyman of the Alaska Department of Fish and Game.

Also, water falling from a ledge above hits the water surface below, and continues to plunge deep below the surface. Then — under pressure from more plummeting water — the water rushes back up to the surface. The continuing falling water acts as a hydraulic jack, squeezing the water back up to the surface. Fish use the “hydraulic jump” water to boost their initial leap, says Webb.

Among Pacific salmon, Lyman says, Coho and steelhead (rainbow) trout are the best leapers because they seek the high river source to spawn. The chum salmon is the poorest leaper. The Atlantic salmon is the best leaper of all salmon.” (source)

Water depth of the pool below the falls and the hydraulic push of the plunging water back upward combine to propel the determined fish.

09
Feb
13

Natural Barriers: Dougan Falls and Wild Steelhead Purity

douganfalls leana jimenez

Dougan Falls on the Washougal River; Photo by Leana Jimenez

Well, almost pure strains of wild steelhead make their way above Dougan Falls on the Washougal River. Natural barriers, in this case a waterfall, seem to act as good obstacles to separate out the inferior hatchery steelhead from the wild steelhead. 

Studies have been conducted over the years to chart the passages of hatchery and of wild steelhead in various watersheds. The Washougal River has no man made barriers, only natural barriers in waterfalls.

“On the Washougal, our data indicate that natural passage barriers (waterfalls) effectively isolate returning wild steelhead from straying, hatchery-origin adults. Above Dougan Falls on the Washougal, less than 3% of returning adults have been identified as hatchery origin. Using this data, WDFW determined this area to be a genetic sanctuary…” (Clark-Skamania FF)

Dougan Falls Bill McMillan Pic

Here is a photograph by the legendary Bill McMillan of a wild steelhead leaping its way up and over Dougan Falls.

The Native Fish Society published a study by Bill McMillan re wild steelhead with references to the Washougal River and Dougan Falls




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