Heading toward extinction
Regarding Dick Sherwin’s May 15 letter: Prior to construction of the lower Snake River dams, smolt-to-adult return ratios for Snake River spring/summer chinook and steelhead were about 4%. This survival rate was adequate for healthy tribal and sport fisheries, with sufficient spawners remaining for population stability.
In recent years, Snake River spring/summer chinook and steelhead, which must negotiate eight dams and reservoirs on their migration to and from the ocean, have had SARs averaging less than 1% for salmon and less than 2% for steelhead. When SARs are less than 1%, this leads to extinction. With less than 2%, depressed populations cannot recover.
The Northwest Power and Conservation Council’s SAR goal for spring/summer chinook and steelhead is 2% to 6%, with an average of 4%.
This is the level of survival Snake River steelhead and salmon had before construction of the lower Snake River dams.
Salmon populations from Columbia River tributaries downriver from the lower Snake River dams, which must negotiate four or less dams, continue to have adequate SARs, even though salmon that enter these tributaries experience the same ocean conditions and predation by birds, marine mammals and piscivorous fish that Snake River salmon do.
The difference in SARs between upriver and downriver tributary populations is due to the number of dams and reservoirs that the upriver and downriver populations must negotiate.
A recent summary of the science is available online. Google: “A review of potential conservation and fisheries benefits of breaching four dams on the lower Snake River.”
Richard Scully
Lewiston
Time and money
Dana Milbank correctly doubts that UFOs have anything to do with space aliens, but he doesn’t discuss the problems that astronomical interstellar distances impose on space travel.
The nearest star outside the solar system, Proxima Centauri, is more than 4 light-years distant. The laws of physics don’t forbid a spacecraft that travels at one-tenth of the speed of light, which would get our astronaut from here to there in 40 years.
People are familiar with the size of a rocket it takes to propel an astronaut to Earth orbit at 7 miles per second. A tenth of the speed of light is 18,600 miles per second, which is 2,657 times faster. Ignoring the small additional amount required by relativity, the energy required increases as the square of the speed. So we need more than 7 million times the orbital energy to propel our imagined rocket.
I doubt a Congress that is even more space alien than our own would appropriate the necessary funds.
Don Matteson
Pullman
