ard their spawning grounds, but some will instead move back downstream over dams," says Keefer. This phenomenon, called fallback by fisheries managers, occurs more often in adults that were barged out as juveniles than in those that migrated naturally.
"It's not clear if they're just running out of steam swimming up the river or if they get disoriented and move back downstream in search of cues from their home river," Keefer says.
The scientists believe that being carried on a barge prevents young fish from learning about important environmental signals during a formative time of their juvenile lives. A barge can take them the same distance in two to three days that would normally take them several weeks, Keefer explains. Traveling great distances by boat in this study, at least 215 miles appears to garble the natural cues these fish use to find their way home. Keefer's results also suggest that transported fish are more likely to stray from their home tributary. If these lost fish often from hatchery populations breed with another wild population, the resulting gene flow can reduce that population's evolutionary fitness.
"Salmon have a life history that represents a long legacy of adaptation to local conditions," Keefer says. "The fish are well-adapted to specific rivers, and when you dilute their unique genetic makeup, it can reduce the productivity of the overall population."
A satisfactory solution is difficult to find, Keefer says. Managers could barge fewer juveniles, but then more fish would die while trying to pass the dams. They could also release more water over dam spillways to help juveniles pass downstream
'/>"/>
| Contact: Christine Buckley christine@esa.org 202-833-8773 Ecological Society of America Source:Eurekalert |
Related biology news :
1. Transporting broiler chickens could spread antibiotic-resistant organisms
2. Bayhill Therapeutics and the Juvenile Diabetes Research Foundation announce research collaboration
3. Salmon garnish points the way to green electronics
4. New paper examines dams effects on California salmon
5. Salmonid hatcheries cause stunning loss of reproduction
6. Understanding, combating foodborne pathogens E. coli 0157 and salmonella
7. UW launches cutting-edge DNA fin-printing project for salmon
8. Fish farms drive wild salmon populations toward extinction
9. Unfavorable ocean conditions likely cause of low 2007 salmon returns along West Coast
10. Hatchery fish outnumber wild chinook salmon in troubled fall run
11. Fruit flies show how salmonella escapes immune defenses
| Copyright © 2003-2012 Bio-Medicine. All rights reserved. ABOUT | CONTACT US | DISCLAIMER | PRIVACY POLICY | TERMS AND CONDITIONS |  |