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salmonid
06-04-2014, 08:17 AM
One more reason to provide fish passage around dams rather than just build hatcheries...


http://registerguard.com/rg/news/local/31676722-75/fish-magnetic-field-hatchery-steelhead.html.csp

A new study suggests that steelhead trout can have trouble using the Earth’s magnetic field to navigate if they were raised in a hatchery, where the field can be distorted by iron pipes.

Scientists at the Oregon Hatchery Research Center in Alsea raised two sets of fish: one outside the hatchery with a natural magnetic field, and one inside the hatchery, where instruments showed that the field was distorted.

Fish raised outside the hatchery oriented themselves to changes in the magnetic field, but fish raised in the hatchery’s distorted magnetic field did not.

The scientists found that when a field was created simulating the intensity and inclination of a spot in the ocean off California in the southern part of the steelhead’s range, most of the fish from the first group pointed northwest and out to sea. When the field was changed to simulate a location off Alaska, the northern part of their ocean range, most of the fish turned to point southeast, toward home. Fish raised in the distorted magnetic field did not orient themselves in any particular direction.

“I would not go out and tell hatchery managers to pull out all the iron pipes and replace them with PVC or aluminum,” said lead author Nathan Putman, a researcher at Oregon State University at the time of the study who is now at NOAA Fisheries Service in Miami working on fish migration questions. “We know it has an effect. What is not clear is whether the fish can recalibrate their magnetic sense after leaving the hatchery, or whether they are confused for the rest of their lives.”

The study was published in Wednesday’s edition of the Royal Society journal Biology Letters.

Peter Moyle, a professor of fish biology at the University of California, Davis, said in an email that the study was “a good demonstration of how fine-turned steelhead and salmon are to their environment.

“The magnetic sense of fish is a relatively new discovery, especially in relation to its importance for navigation,” he added. “This study nicely shows one more reason why we need to keep maintaining wild populations of salmon and steelhead and not just rely on hatcheries.”

whalonem
06-04-2014, 08:37 AM
Interesting read. In my view still having some fish in the system is better that none. If we had no hatcheries we would have no fish, we just have to much pressure on the the few natural breeders in the system. In my opinion build more and better hatcheries and double the population. Unfortunately, the purest don't see the value in our kids catching fish vs. reading about them. Really, we all have to look at the broader picture vs.the details. Just think of all the benefits of having our kids out in the fresh air growing up the way we did. Buy them a rod and reel and old PC. that so big they can't carry it with them every where. PLANT MORE FISH!!!!!! Whalonem

salmonid
06-04-2014, 03:18 PM
I agree with you 100%.


In my view still having some fish in the system is better that none.