Is it a coincidence that one of the world’s largest mineral deposits is near the largest sockeye salmon spawning grounds at Bristol Bay? And if a massive mine like Pebble removed those deep deposits that create the world’s magnetic field – could it disrupt salmon’s ability to find their way home?

A study underway aims to find out.

It’s not even been 10 years since we’ve discovered that salmon are using Earth’s magnetic field as a way to know where they are to make important decisions. People have thought about what is the magnetic environment that salmon need to thrive? And what might humans be doing to that magnetic environment that might keep them from thriving?”

Dr. Nathan Putman is a Senior Scientist at LGL Ecological Research Associates and a top expert on animals’ use of magnetic fields in migratory navigation. 

“So with this particular project what we’re aiming to do is be proactive in terms of not leaving stones unturned, to think about might removing magnetic minerals alter the magnetic landscape experienced by salmon? And to what extent. So thinking about how we might be presenting salmon or other species that we we care about with challenges from how we’re manipulating their habitats.

Putman’s earlier studies on pinks show that salmon have multi-purpose navigational tools.

“A compass by itself only gives you a direction. The Earth’s magnetic field obviously gives you that direction. But for salmon it also gives you a sense of where you are. So it lets you know where in the Bering Sea or where in the Gulf of Alaska you might be. In some ways you can think of it as part compass, part GPS.” 

A salmon’s early magnetic rearing environment is critical, Putman says, and it’s easy to manipulate in the lab.

“We call them magnetic displacement experiments. And they perform quite well, they seem to know how to orient their movements when they grew up in a pristine magnetic environment. But if you add something as simple as a nearby iron pipe to that rearing environment, that distorts the magnetic field.   Then you have the same family of fish, the same setup, the same sort of behavioral assays that they’re presented with  and they do not perform well. They don’t appear capable of using the magnetic field to make navigation decisions.”  

Putman is testing models for over 300,000 mines spanning 20 years to gauge impacts on fluctuating geomagnetic fields. His results should be known by this summer.

The project is funded by Arron Kallenberg, CEO of Wild Alaskan Company and a third generation fisherman at Bristol Bay.