Magnetic force

[PennypackFlyer]

Yesterday as I read my Fly fisherman magazine I began thinking about fisheries and methods of how fish find there way back to spawn.
So the question is: do salmon and other migratory fish have a magnetic signature that returns them to their spawning grounds or is it more DNA related?

 

[Chaz]

Well yes if you want to call it that. All stones and rock have a magnetic signature when they are formed, so the magnetic art is is the front of the head and 'reads' the magnetic signature in the stones. The exact process is not clear to me, but that's the gist of it.
They are supposed to also use scent sensors on the front of the head when they get close to their home streams.
Humans are supposed to have magnetic material in their nose to help guide them, but as we know some humans are shortchanged and get lost easily.

 

[bikerfish]

hmm, I'm gonna tie some magnet particles to some flies!

 

[salmonoid]

Chaz wrote:
Well yes if you want to call it that. All stones and rock have a magnetic signature when they are formed, so the magnetic art is is the front of the head and 'reads' the magnetic signature in the stones. The exact process is not clear to me, but that's the gist of it.
They are supposed to also use scent sensors on the front of the head when they get close to their home streams.
Humans are supposed to have magnetic material in their nose to help guide them, but as we know some humans are shortchanged and get lost easily.

Not gonna work on an individual stone or even bedrock basis, as metamorphism and geologic processes will realign magnetic structure in rocks. Further, there's no way an anadromous fish in the ocean or a lake can sense the magnetic signature in a rock hundreds of miles away. However, it would work if there were a way for fish to sense earth's magnetic field structure somehow, which is what scientists are now suggesting.

Which means not necessarily tying a magnet in your fly, but figuring out how to get a machine to haul along with you to induce a magnetic field that will locally attract fish

 

[PennypackFlyer]

Salmonoid:
I hope they never come up with a machine to do all that except for reasons like getting rid of the asain carp or some of the other invasive species.
(I know that when a ship is built/created/welded it has a magnetic signature. For our own stocking: If fish also have a similar magnetic signature than we have to fertilize them at the location where we want to stock them and not before then. I think that we would want the forces that draw them towards their spawning grounds to be pure. If they are fertilized elsewhere's they may be confused as to which river/lake they belong to. And thus migrating to areas that they don't belong. I know that this sounds a little deep. But it may be an answer to solving one of life's riddles (how to feed the multitudes) or the problem that is going on with removing the asain carp from our waters.)
P.S. Chaz: It's strange that I was born in Utica, NY in 1960 and now I find myself drawn to that location! It maybe more than just the Salmon River fishing!

 

[Chaz]

Fish do sense the magnetic poles, I sorta left that out, but once they get to the mouth of there home water they are able to pick up the signature in the rock.
Well metamorphism and geologic processes happen over very long periods of time and the rocks are fairly stable with the magnetic configuration until the rock is melted the next time. Geologists use the magnetic signature of rock to determine where it came from, for instance the bedrock from NYC in Central Park was form when NA collided with North Africa, and one plate was pushed under the other resulting in massive lava flows. When the continents drifted apart the rock moved over 1000's of miles, but still has the same magnetic signature.

 

[pcray1231]

I think the method of fish "sensing" the home waters has largely been solved, though questions still remain.

Smell. We've shown, for instance, if you plug a salmon's scent receptors, it becomes disoriented and struggles to find it's home stream. And this has also been shown to be the reason that a portion of every population gets "lost" and returns to the wrong stream. Those "lost" fish, for various reasons, have been shown to have worse senses of smell than the ones that made it to the "right" place. Sometimes it's disease, genetic anomalies, injury, exposure to contaminants, etc.

All waters have a unique chemical makeup, and obviously, fish are sensing this and seeking out their "home" waters. The open questions are about what specific chemicals matter for each species? Is it natural water chemistry stuff, like calcium, phosphorus, etc.? Or is it pheremones? Fish respond VERY strongly to things like amino acids.

 

[JeffK]

Sharks, skates, and rays have large electro-magnetic field sensors and it seems likely that that they use them to detect the Earth's magnetic field. This acts like a built in compass. The interaction between the Earth's magnetic field, ocean currents (Hall effect), and the solar ion flux also sets up an electric field around the Earth that sharks can sense. As an aside, the two sides of the Atlantic are routinely 20V apart and can be 2000V apart during a solar storm. The ground potential between Minneapolis and Fargo, ND was 800V once in a solar storm.

The electrical sensitivity of sharks' sensors is about 1 microvolt/cm. This allows them to detect the E/M Earth fields, and more importantly the E field around bait fish, but I think the trapped magnetic fields in rocks are below the sensitivity of sharks. That's just a gut feel from the crazy set-ups geologists use to measure the magnetic fields in rocks.

Sharks and rays have been studied quite a bit (I did work on sharks in the late 1980s and early 1990's because of shark attacks on undersea communication cables). I'm not sure if salmonids have the capabilities of the sharks and rays, but I remember work that they have some electrical field sensing capability.

 

[KeithS]

It scares me that people know this stuff.

 

[PennypackFlyer]

JeffK
That may better explains why animals will chew on electric wires.
I also believe that humans can sense this magnetic field, we may not fully understand it at this point. However we have all seen the magnetic bracelets that are suppose to better our health. Maybe alot of our illnesses are caused by us moving around the world to much and not keeping in touch with our magnetic force?

 

[pcray1231]

Regarding the bracelets; Placebo effect. The effect is real and all, so if you believe in it, it may help you, and more power to you. But oh, umm, I guess I just ruined it?