so they can release gas out
swim bladder.
swim bladder is what helps the fish stay afloat without the swim bladder a fish would simply sink duhhh
swim bladder.
Bony fish have a swim bladder that helps them regulate their buoyancy and control their depth in the water. By adjusting the amount of air in the swim bladder, bony fish can increase or decrease their buoyancy, allowing them to float or sink as needed.
That would be the swim bladder.
swim bladder
to move up and down in water
to move up and down in water
Swim bladder
Basically, any fish with a swim bladder and movable pectoral fins can swim backward (bony, ray-finned fish).
The swim bladder keeps the fish upright in water.
All fish have swim bladders. The bladder is what enables them to maintain buoyancy in the water. Without it, they would have to constantly swim up, much like birds have to fly up in the air. It is too much work to constantly swim up, so using a swim bladder, fish do not have to exert as much effort, and preserve energy.