Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Transporting Juvenile Salmon Hinders Adult Migration

Scientists have discovered that management efforts intended to assist migrations of salmon and steelhead trout can have unintended consequences for fish populations. Juveniles that are transported downstream on boats can lose the ability to migrate back to their breeding grounds, reducing their survivorship and altering adaptations in the wild.

Transportation programs have been in place for over three decades to improve the survival of fish that hatch in rivers but migrate downstream to the ocean, where they live most of their adult lives. Adults then swim back up the river to mate, lay eggs and finally die in the same area where they were born. These fish can travel hundreds of miles and make dramatic ascensions up waterfalls and past dams.

When dams block rivers, however, the migrating fish – especially juveniles – can have a tough time traveling between their spawning grounds and the open ocean.

“Juveniles trying to get back to sea usually go over the spillways or past the dam’s turbines,” says Matthew Keefer, a biologist at the University of Idaho and the lead author on the study, which appears in the November issue of Ecological Applications.

Going past a dam’s turbines, however, can kill many young fish. In response, management efforts help salmon and steelhead trout avoid dams altogether by transporting juveniles past dams toward the ocean on river-faring barges.

But Keefer has found that this free ferry ride can create problems when the juveniles grow up. He and his colleagues Christopher Caudill, Christopher Peery and Steven Lee at the University of Idaho tracked the movement patterns of adult salmon and steelhead trout along the Columbia and Snake rivers in Washington and Oregon. They found that, when compared to fish that migrated naturally, transported juveniles had lower survivorship as adults and were less likely to find their way home.

“Adult fish usually move steadily upstream toward 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, but that would reduce the amount of energy the dams produce. A third option is to slow down the barges so the trip resembles the time it takes juveniles to swim to the ocean. But boats are a stressful environment for fish, and the close quarters within the ships increase the risk of disease.

“It’s tough to find a solution that could handle all the challenges in this system,” Keefer says. Scientists and salmon managers hope to find the ideal solution: one that would preserve native fish populations and maximize their survival while keeping the integrity of energy-producing dams.

To access images associated with this article, please contact Christine Buckley at or at (202) 833-8773 ext. 211.

The Ecological Society of America is the world’s largest professional organization of ecologists, representing 10,000 scientists in the United States and around the globe. Since its founding in 1915, ESA has promoted the responsible application of ecological principles to the solution of environmental problems through ESA reports, journals, research, and expert testimony to Congress. ESA publishes four journals and convenes an annual scientific conference.

Christine Buckley | Newswise Science News
Further information:

More articles from Ecology, The Environment and Conservation:

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

nachricht Malaysia's unique freshwater mussels in danger
27.09.2016 | The University of Nottingham Malaysia Campus

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>