hatcheries’ metal can disrupt steelhead magnetic sense ...
Trout, like many other animals, sense the Earth\'s magnetic field and use it as they migrate.
However, marine biologist Nathan Putman said that small fish raised from steel bars on pipes and concrete floors could not be properly oriented in a simulated magnetic field, now at the Southeast Fisheries Science Center in Miami.
In a recent study, Putman concluded that young migratory fish can inherit their magnetic maplike sense of the future range.
But the confusion of fish in the new test shows that scientists need to consider experience and genetics, June 4.
If the early effects of the magnetic interference home persist in the later stages of the life of the fish, new experiments may begin to explain why the hatchery fish often fail to return to the expected spawning ground.
Puttman says these rainbow trout \"are a big deal for a lot of people.
\"Both commercial fishing and sports enthusiasts cherish them and Pacific tribes think they are part of their heritage.
Rainbow trout belong to the same species.
Rainbows spend their lives in fresh water, but steel heads swim to the sea and return to fresh water to spawn, often finding the streams they hatch.
Steelhead\'s lifestyle requires precise navigation, and the ignorance of fish from magnetic twisted tanks adds a twist to the unfolding story of how salmon and their close relatives use the Earth\'s magnetic field to find their way.
Real navigation requires both a compass to identify the direction and a map to indicate the direction and distance of the way forward.
Young Chinook salmon inherited their map version in February without having to learn.
Even before they tasted the salt water, the young Chinook responded to Puttman\'s simulation of the marginal magnetic field of their future foraging range in the ocean.
When placed in a bucket, the fish tend to stay away from the range boundary of the simulation as if they already knew to swim back to the center of their territory.
But now, Putman has found that both maplike sense salmon and trout are able to respond to changes in the environment.
In a new test at the Oregon Hatchery Research Center in alsey, steel heads are too small to even start leaving fresh water, if they grow up in hatchery tanks with a geographically normal magnetic field, it is likely to be far from the simulated magnetic boundary.
Small fish raised in a magnetic twisted fish tank
Caused by iron pipes buried inside and concrete steel bars nearby
The normal map direction cannot be used. (
Wires and equipment also distort the magnetic field. )
James Gould of Princeton University says the fish does inherit the basis of the magnetic sense, but \"the system needs initial calibration.
Gould studied animal navigation but was not involved in the project.
He suspected that the fish needed to undergo a change in the magnetic field when moving.
Whether the experimental fish growing up in the weird magnetic field will lose its way for life or not, if there is no further test, Putman cannot say.
He suggested that with more time in an area without distortion, confused fish might straighten out their maps.
If they don\'t, the test can help explain some of the problems people have with raising fish in captivity.
\"Everyone is disappointed with hatching fish,\" Putman said . \".
Advocates of fish farming to supplement the wild population lament the inefficiency of the hatchery, and it is disturbing that very few released teenagers resume spawning.
Critics of the hatchery project warn that artificially raised fish tend to mate in the wrong stream, thus staining the gene pool of the locally adapted wild population.
Both disappointment may be the result of failure.
It\'s too early to say, but Putman admits that if you raise fish in a strange magnetic field, the fish may \"not sail well.