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Fish can stay in one spot with little effort also because they have a special organ called the swim bladder. They can fill it up with gas and this allows them t

Fish can stay in one spot with little effort also because they have a special organ called the swim bladder. They can fill it up with gas and this allows them to maintain their position without actually swimming.

bombcar 5y ago
Doesn't the swim bladder just help them calibrate depth in the water?
- the_af 5y ago
  I don't think the parent commenter is saying the swim bladder is all that matters. There is an "also" hidden in their sentence :)
- locallost 5y ago
  I'm not an expert, I just had to learn the basics recently to get my fishing permit. But the explanation given was that its function is allowing the fish to float / hold their position and save energy. Carps even have two chambers since they are bottom feeders and they can tilt their bodies mouth down more easily this way.
  - krisoft 5y ago
    Yes. What you are talking about is a fish keeping a fixed depth. Having a swim bladder enables the fish to attain neutral buoyancy. That way the fish doesn't need to expand energy to keep itself from sinking or floating up. What the article is talking about is position keeping against the current in flowing water. Swim bladder is good for up-down position keeping, the article's phenomenon is good for forward-backward position keeping. Interestingly there is a way to use a swim bladder like construct to propel one forward. Underwater gliders do this, and the process is very energy efficient. The way it works is that the glider uses its variable buoyancy device (an artificial swim bladder) to set a negative buoyancy and starts sinking. The wings of the glider turn this downward motion into forward speed. At the target depth the glider expands some energy from its batteries to set a positive buoyancy and keeps the forward momentum as it is ascending. Because of this they only need to use energy at two points (at the top and the bottom) in their saw-tooth like swim profile, and they can travel thousands of kilometers on a single charge. https://en.wikipedia.org/wiki/Underwater_glider https://en.wikipedia.org/wiki/Underwater_glider
- nanidin 5y ago
  I think so. Scuba divers use a BCD (buoyancy control device) that sounds similar - it's used to control buoyancy only.
- kuhewa 5y ago
  Yes, although it probably does have some role in swimming efficiency due to obviating lift generation to get from a to be at the same depth. OTOH especially for laterally compressed fishes, there is a metabolic cost of all the paired and medial fin movement required just to stay oriented in the water column, and they may be able to save more energy by deflating and sitting on the bottom.

bombcar 5y ago

Doesn't the swim bladder just help them calibrate depth in the water?

the_af 5y ago
I don't think the parent commenter is saying the swim bladder is all that matters. There is an "also" hidden in their sentence :)
locallost 5y ago
I'm not an expert, I just had to learn the basics recently to get my fishing permit. But the explanation given was that its function is allowing the fish to float / hold their position and save energy. Carps even have two chambers since they are bottom feeders and they can tilt their bodies mouth down more easily this way.
- krisoft 5y ago
  Yes. What you are talking about is a fish keeping a fixed depth. Having a swim bladder enables the fish to attain neutral buoyancy. That way the fish doesn't need to expand energy to keep itself from sinking or floating up. What the article is talking about is position keeping against the current in flowing water. Swim bladder is good for up-down position keeping, the article's phenomenon is good for forward-backward position keeping. Interestingly there is a way to use a swim bladder like construct to propel one forward. Underwater gliders do this, and the process is very energy efficient. The way it works is that the glider uses its variable buoyancy device (an artificial swim bladder) to set a negative buoyancy and starts sinking. The wings of the glider turn this downward motion into forward speed. At the target depth the glider expands some energy from its batteries to set a positive buoyancy and keeps the forward momentum as it is ascending. Because of this they only need to use energy at two points (at the top and the bottom) in their saw-tooth like swim profile, and they can travel thousands of kilometers on a single charge. https://en.wikipedia.org/wiki/Underwater_glider https://en.wikipedia.org/wiki/Underwater_glider
nanidin 5y ago
I think so. Scuba divers use a BCD (buoyancy control device) that sounds similar - it's used to control buoyancy only.
kuhewa 5y ago
Yes, although it probably does have some role in swimming efficiency due to obviating lift generation to get from a to be at the same depth. OTOH especially for laterally compressed fishes, there is a metabolic cost of all the paired and medial fin movement required just to stay oriented in the water column, and they may be able to save more energy by deflating and sitting on the bottom.