Question about oarfish (with pictures!)

The oarfish is a long, thin fish which has probably been mistaken for a sea serpent. Its about 10 to 50 feet long, and lives deep in the ocean at a depth of about 3000 feet. One of the many strange things about it is its tendency to swim vertically, with its head pointing towards the surface of the ocean. My question is, why would it evolve to swim like this? What advantage does this strategy give the oarfish?I was thinking that maybe it helps it to eat - they filter small crustaceans out of the water but many other animals do this too and don't swim upright. Does anyone have an answer?I found some pictures of oarfish:

Dear Gary,Oarfishes were also observed in shallow water, but rarely drift on the shore.
Your question: The strategy could be a fine adapation to vertical swimming (up/down)daily. Many beasts depending of the plankton do such daily migration. This is an assumption. I'm more familar with sharks.Have a nice day.Denesha

Although I do not know much about oarfish, and I doubt many people do, I do know that an evolutionary next-step doesn't have to be one where the organism have gained an advantage. It could simply be a random mutation that does not cause any harm or give the creature a disadvantage in its environment.For example, if you examine a snake's skeletal structure, you will find that it actually have leg bones, though not much of it. Those structures are left overs from when they lost their limbs in the distant past. Now, what possible purpose could those parts of their skeleton have? Absolutely nothing. It doesn't cause any harm or give the snake any disadvantage, though. So, the question really is, "why not?"

Thanks for the replies! It makes sense that it may follow plankton, or that it simply swims upright because of a mutation. Its a very strange creature.

A common sense answer could be station keeping in ocean currents. With a log body it would be extremely difficult for the oarfish to constantly fight the ocean currents....if it turns upright and turns like a knife into the current there is much less drag created and it is easier for it stay in place while feeding.

um, no.that position would have more resistance to the ocean currents, resistance being proportional to the square of relative speed and proportional to the maximum cross-sectional area perpendicular to the line of {movement \ current \ resistance} andthe fish would have very poor ability to move in a manner to keep station in that position.Rather, it could be using it's long body like a sail to take advantage of such currents, moving up and down like a hot-air balloon to find the most advantageous one.

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we are limited in our ability to understand
by our ability to understand RebelAAmerican.Zen[Deist
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semantics...one mans drag is another mans resistance...it's operating like a rudder

If you were both saying the same thing it would be semantics. One man's drag is another man's resistance, but she's saying resistance would increase, and you said it would decrease. It doesn't matter whether it's operating like a rudder, what you said was inaccurate.