I would ask one thing going back to arguments we had a month or so ago, would the ones that don't leave be considered salmon, or trout? 
Salmon of Small Stature Endowed with Mating Advantage
Science - SPACE.com/LiveScience.com
Picture the wee little salmon. Choosing not to go to sea, he's waited for a mate for what seems like a lifetime in a streambed in the mountains of Idaho. Months and months go by, perhaps years. Finally she arrives, and she's a whopping 20 pounds. He, having stayed behind, never got bigger than six inches.
Yet the pan fry has the same desire to mate. And, apparently -- all size jokes aside -- the same ability.
In fact, salmon of small stature appear to share an advantage when it comes to getting the girls.
"Small males can sometimes fertilize many eggs by sneaking rather than by fighting," writes University of Washington professor Thomas Quinn in his new book with the not-exactly-sexy title, "The Behavior and Ecology of Pacific Salmon and Trout."
Though the lack of travel stunts their growth, the little devils get to avoiding the sharks, fishermen and dams that imperil the wild journey to the ocean and back.
Why a handful of salmon stray -- by staying put -- remains a mystery, however. The tendency may be rooted in age-old climate changes.
"These strays are not merely an aberration to be ignored," Quinn says. "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."
Quinn speculates that adults spawning in unpredictable streams and rivers - those where spawning conditions vary wildly from year to year -- may be genetically inclined to produce more offspring that are likely to stray. (A related trait of the Chinook has siblings returning to spawn in different years -- another weapon against annual unpredictability.)
In the book, Quinn notes that a lot of salmon habitat is no longer accessible to the fish. The ability of strays to keep a population going, however, is cause to continue working to restore habits, he argues.
Salmon of Small Stature Endowed with Mating Advantage
Science - SPACE.com/LiveScience.com
Picture the wee little salmon. Choosing not to go to sea, he's waited for a mate for what seems like a lifetime in a streambed in the mountains of Idaho. Months and months go by, perhaps years. Finally she arrives, and she's a whopping 20 pounds. He, having stayed behind, never got bigger than six inches.
Yet the pan fry has the same desire to mate. And, apparently -- all size jokes aside -- the same ability.
In fact, salmon of small stature appear to share an advantage when it comes to getting the girls.
"Small males can sometimes fertilize many eggs by sneaking rather than by fighting," writes University of Washington professor Thomas Quinn in his new book with the not-exactly-sexy title, "The Behavior and Ecology of Pacific Salmon and Trout."
Though the lack of travel stunts their growth, the little devils get to avoiding the sharks, fishermen and dams that imperil the wild journey to the ocean and back.
Why a handful of salmon stray -- by staying put -- remains a mystery, however. The tendency may be rooted in age-old climate changes.
"These strays are not merely an aberration to be ignored," Quinn says. "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."
Quinn speculates that adults spawning in unpredictable streams and rivers - those where spawning conditions vary wildly from year to year -- may be genetically inclined to produce more offspring that are likely to stray. (A related trait of the Chinook has siblings returning to spawn in different years -- another weapon against annual unpredictability.)
In the book, Quinn notes that a lot of salmon habitat is no longer accessible to the fish. The ability of strays to keep a population going, however, is cause to continue working to restore habits, he argues.
