The process of straying is entirely mysterious, Quinn says. Do strays identify the home stream but then go elsewhere? Do they have poorer memory or sensory capabilities and so stray out of ignorance? Or are there other factors involved?
"These strays are not merely an aberration to be ignored. Much of the present range of Pacific salmon was covered by thick glaciers some 10,000 to 15,000 years ago, so most current populations were founded by strays since then. Thus straying is just as fundamental an attribute of salmon as homing," he says.
"Perhaps the offspring should be called strays only if they are unsuccessful when it comes time to reproduce, and colonists if they are successful."
From an evolutionary perspective, a mixture of homing and straying by offspring is a way that parents can spread the risk because offspring don't spawn in the same place. One of Quinn's hypotheses is that adults spawning in less predictable streams and rivers ?ones where conditions are good some years and bad in others -?may be genetically inclined to produce more offspring that are likely to stray.
Then there are salmon like the chinook where brothers and sisters from the same parents don't mature and return from sea at the same time, a way of "straying in time" so that a given pair hasn't lost all their descendants if one year's worth is wiped out. There is undoubtedly an environmental aspect in all of these, he says. The most obvious being when conditions in the home river are so degraded that salmon move elsewhere to spawn.
Straying is just one of the traits that cause Quinn to say that salmon have chances to recover from years of declines "if we would only take our collective foot off their neck."
"A great deal of habitat from southern British Columbia to California is no longer accessible to salmon or has been altered to their detriment," he writes in the conclusio
Source:University of Washington