A while ago, I was watching salmon spawn while visiting a friend who is fortunate enough to live on the banks of the Rogue River. It was a first for me, and it was wonderful to see the wild fish splashing around in the shallows.
But a few days later the first of those winter storms came along and washed a lot of water and debris down that river. I am wondering if the salmon eggs also washed away. Do you know?
— Dodie S., Medford
We took your query to local piscine experts at the U.S. Fish and Wildlife Service and got the whole soggy story, Dodie.
According to Mary Burnham-Curtis, senior forensic scientist, the rains probably did wash away quite a chunk of the salmon eggs.
Not to worry, however, Burnham-Curtis says, there are plenty of fish left for fishing.
It is fun, she agrees, to watch the female salmon set up their nests by sweeping their tails over the gravel, clearing a space in which to deposit thousands of eggs. This nest is called a "redd," and it can be 2 to 10 feet long and 1 to 6 feet wide. Redds are ideally located in a well-oxygenated section of the river that has an upwelling of water.
The dominant male aligns himself next to the female for the spawning ritual. The female releases her eggs and the male releases his milt. Fertilization happens in the water while the eggs drift down to the bottom of the river (or stream).
After the eggs have settled, the female swims upstream and uses her tail to cover the nest of eggs with clean gravel.
The female will then proceed to dig another redd at a nearby location, and the male will accompany her to protect the area.
For all Pacific salmon species, spawning is the final act before dying. (Steelhead can make the trip from fresh to salt water and back again. But they are rainbow trout, not salmon.)
Feeling bad for our salmon? Don't. It's all a cycle, Dodie. The adult salmons' decomposing bodies will provide food for other species over the winter, and also help fertilize the rivers and streams.
A percentage of the eggs will fall prey to predation before they hatch, including many of those flushed from their nests in the rushing water, Burnham-Curtis said.
But thousands upon thousands will remain safely nestled in the river's crooks and crannies.
"They settle into the riverbed," Burnham-Curtis said. "They sink down beneath rocks and into crevasses."
The eggs usually hatch in 30 to 90 days, or a little more, depending on water temperature. Once the embryos hatch, they will live off their yolk-sak on their underbellies before they begin their search for food as fry.
Some species of salmon head toward the ocean just weeks after hatching from their gravel birthplace. Others stay in the freshwater streams for up to two years before migrating to the salty sea.
The smolts will become full adults in the ocean and eventually return to freshwater, many to the site where they were laid.
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