Fish Adapt

The volcano blew its top. A few million tons of earth shifted. Clouds of red-hot gasses and ash scorched branches and bark off trees. The rivers looked like mudflows, boiling downstream, taking out bridges and houses on the banks. How would we ever recover?

Soon thereafter while fishing for sturgeon nearly a hundred miles downstream, we had to dodge thousands of stripped trees that had floated all the way from the hills near Mt. St. Helens. The Columbia River was afloat with millions of chunks of pumice. What a disaster! Strangely enough, the sturgeon fishing was still good. But that’s not what this story is about!

Within a couple of years, hundreds of bright salmon were fighting back up the streams to spawn near the great mountain. Soon, steelhead and salmon were back, filling those same steams that gushed with superheated gray ash just a few years before.

With all the talk of endangered species and declining runs, sometimes we don’t really give nature her due. Species are adaptable. They wouldn’t have survived for thousands of years without the ability to adapt and thrive in a variety of challenging situations. Salmon are classic examples.

Gaining Strength
To thrive and multiply in food-starved waters, salmon adapt to the challenge by traveling many miles downstream to enter brackish and then salt waters to feed in a richer environ. In the process, they gain size, strength and power and return to their home rivers, sometimes after hundreds of miles of effort, to start out the next generation.

Contrary to popular belief, they don’t all return to the stream of their birth. A few will stray and test the waters of other streams on their way home. That way a stream that had lost its population due to a logjam or maybe a crazy volcano, might, in time, rebuild its population.

One little known trait of the salmon species is its ability, like a chameleon, to change colors to blend into the environment. As fishermen who chase the fish know, when salmon are in their native streams as fry, they have lots of spots and lines that help them to blend to the bottom of the stream. When they head out to the ocean, they develop clean, white bellies that look like the sky when seen from below, and dark gray dorsal skin that looks like the ocean depths when viewed from above—safety from predators all around.

Fish Experiment
I recently got an interesting e-mail and set of photos from our local fisheries instructor at Astoria High School, Lee Cain. Lee is a very energetic and fun instructor who encourages his students to learn more about aquatic life forms by conducting their own experiments. One of his advanced students, Henry Brause, came up with some very interesting results. Here is the substance of the proud instructor’s e-mail to me:

“Senior Fish Technology student Henry Brause carried out a diet comparison study with Rogue stock Chinook fingerlings this year in blue plastic barrels. An interesting accidental observation was also made. Most tanks were blue on the inside, but one was a more bleached out green color.

“Attached are some rather large photos that show how the fingerlings changed color to match the background. The rather coho-ish looking green fingerling was in the green tank, while the bluer fish were in the true blue tanks. I have not edited the photos at all. I left them high resolution so that the chromatophores can be better seen. You can actually see the difference in the black pigment cells—much smaller in the blue fish, and the blue chromatophores show up too.

“Guess what studies I am going to encourage next year among the fish technology students!”

The photos were amazing. The fish in the blue tank were bright blue; those raised in the green tank, dark olive! No wonder you might have a little trouble spotting those salmon and trout in your favorite stream; they are disguised as the bottom, even if it turns bright blue!
Now you have an excuse when you get skunked chasing salmon. They can adapt to everything faster than you can!

Bob Ellsberg’s column, Fishin’, appears monthly in RV Life and rvlife.com.