This is the first study of its kind and is carried out by an international team of scientists that includes researchers from the University of British Columbia. Their findings will appear in the October 28 issue of the open access journal PLoS Biology, published by the Public Library of Science.
The team compared the survival rates of out-migrating, juvenile spring Chinook and steelhead salmon from two river basins: the heavily dammed Snake and Columbia Rivers and the free-flowing Thompson and Fraser Rivers – both critical spawning grounds for numerous salmon species.
Using technology that has only recently been available, the team electronically tagged juvenile salmon (smolts) and monitored their journey from freshwater into the ocean via a large-scale acoustic telemetry system called the Pacific Ocean Shelf Tracking (POST) array.
"It came as quite a surprise to us that the Fraser River salmon populations studied have lower survival than the Columbia River study populations," says Erin Rechisky, one of the study authors and a PhD Candidate in the UBC Dept. of Zoology.
Rechisky stresses that there is not yet sufficient evidence to reach any conclusions. "Clearly dams are not good for salmon. What is unclear is whether the Fraser River has a problem that cuts salmon survival to that of a heavily dammed river, or whether factors other than dams play a larger, unsuspected role in salmon survival."
Only in recent years have acoustic tags become small enough for scientists to implant them into juvenile salmon and track them as they migrate downstream. These innovations enabled the team to gather data on salmon smolts in the Fraser River. Before that, it was only possible to measure juvenile survival where salmon gathered in dam bypasses like those in the Columbia and Snake Rivers.
The lower Columbia and lower Snake Rivers currently have eight major hydroelectric dams combined. During the late 1930s when the first dams began to go up, salmon survival rates began to plummet, hitting mortality highs during the 1960s and 1970s due to a combination of warmer waters, fish-grinding turbines and new predators. Since then, the U.S. government has invested in major restoration measures to improve salmon survival rates.
Current conservation efforts have focused on helping smolts pass through the hydropower system. However, the scientific team aims to clarify with future studies using POST technology whether dam passage in itself has long-term detrimental effects that impact salmon's ocean survival.
The researchers note that threats beyond the rivers are taking a heavy toll on salmon. These include habitat destruction, competition with hatchery fish, harvesting and large-scale changes in ocean climate.
Lorraine Chan | EurekAlert!
How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.
Using drones to estimate crop damage by wild boars
12.12.2017 | Gesellschaft für Ökologie e.V.
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
13.12.2017 | Health and Medicine
13.12.2017 | Physics and Astronomy
13.12.2017 | Life Sciences