A steelhead biology lesson

By Allen Thomas, Columbian outdoors reporter

Published:

 

Anglers in Southwest Washington take for granted there are two races of steelhead, mostly winter-runs from November to March and mostly summer-runs from April to October.

In reality, that’s a bit of a rarity in wild populations. Many streams — especially those close to the coast — just have winter steelhead. Many streams — interior rivers east of the Cascade Mountains — just have summer steelhead.

But locally, in the Kalama, East Fork Lewis, Washougal, Wind and Klickitat rivers, there always have been wild runs of both summer and winter steelhead.

Steelhead biology was discussed for hours at a time in the citizen work group that eventually recommended the East Fork of the Lewis be designated a wild steelhead gene bank and the planting of hatchery-origin steelhead cease.

One of the asides learned through all the discussion was this: Winter steelhead generally outcompete summer steelhead over evolutionary timescales.

There are reasons why winter steelhead are more fit, said Thomas Buehrens, a research scientist with the Washington Department of Fish and Wildlife in Vancouver.

Winter steelhead are bigger than summer steelhead of comparable ages when they spawn, and this should tend to result in better reproductive success, he said. This occurs because summer steelhead forego feeding opportunity.

“A typical winter run will continue to feed up to the point when it rapidly migrates upstream to spawn, whereas a summer run will enter freshwater four months to a year before spawning,’’ Buehrens said. “The summer run has therefore sacrificed a growing opportunity.’’

Summer steelhead also must use energy reserves to survive a longer pre-spawn holding period, leaving less energy for reproduction. They may also be susceptible to more threats due to this longer holding period.

“They are basically sitting ducks during low, warm-water periods and may face numerous predators that are either not present or not as active when winter runs are around,’’ he said.

Winter steelhead often repeat spawn annually, while summer steelhead usually repeat spawn two years after initial spawning.

Both races spawn in late winter-early spring then head back to the ocean and feed themselves to health.

Winter runs can return to the ocean in spring and have all summer and fall to fatten up before returning in the winter. Summer steelhead need an extra year in the ocean.

Given the advantages winter steelhead have, why have summer steelhead persisted?

“The answer many of us have come up with is access,’’ Buehrens said. “Summer run spawning areas are only found where access for winter runs is difficult.

“In short, summer runs are only found in coastal watersheds with substantial sections that fish cannot easily ascend in the winter, this means reaches above canyons or waterfalls where high flows and low temperatures hinder the passage of steelhead in the winter months.’’

Buehrens said examples of those canyons or waterfalls are Kalama Falls on the Kalama River, Horseshoe Falls on the East Fork Lewis River, Dougan Falls on the Washougal River, Shipherd Falls on the Wind River or Lyle Falls on the Klickitat.

Large, inland watersheds like the Snake River and its tributaries favor summer steelhead.

“The migration distance and duration alone are enough to necessitate entering the river well in advance of spawning,’’ he said.

So, unless there are waterfalls as blockages or long, long travel distances, biology favors winter steelhead.