Another upside down cave fish

[Islandbound 1]

I went back into a cave for some photos when through the viewfinder this blue fish swam by. I was only able to swing the camera enough to take this one photo before the fish vanished into the cave and never came back. What is it?

 

[Rocha 0]

I think it is a longfin (genus Assessor). Where was it taken?

[Islandbound 1]

Off the coast of Okinawa. Why are all these fish swimming and floating around upside down?

[acroporas 0]

From Japan. Location would make it Assessor randalli.

 

 

Upside down or right side up is all a matter of opinion. Fish are perfectly neutrally bouyant underwater. This means that gravity does not have to be the most important factor in determining which side is up. As such, most reef fish use visual cues to determine vertical orientation. Many fish factor the position of the sun into the equation, but cave dwelling fish rarely see the sun so which ever hard surface is closest they consider down.

 

In their oppinion, you are the confused one, impoperly oriented relative to the cave wall.

[Cerianthus 55]

Fish don't rely solely on visual reference determining their position. In the skull they have similar structures like our inner ear. In fish, a small bone structure (called otolith) is surrounded by cells that can sense its movement or relative weight. They use it to hear, but can also use it to determine their position.

 

However, unlike us, they life in an entirely 3D world and since fish apparantly dont feel uncomfortable swimming upside down, visual cues are important like Acroporas said..... In that case, safety near the wall is more important.....

[ce4jesus 1]

The US Navy in WWII discovered that some pilots would exit cloud banks upside down while others right side up. I can't remember the name of the phenomenon but the Navy studied it at length and determined that the upside down pilots didn't perceive they were upside down and would right themselves once they had a visual reference.