At the bottom, and deep-sea fishes swim bladder not. First, there is no need to ascend, secondly, swim bladder at great depths just useless - at a high water pressure that exists at depth, the gas from it immediately squeezed out would be out.
How did these fish is buoyancy? At the expense of fat. First, it reduces the density of the body, and secondly, the fat incompressible. In conditions of great pressure at depth is a very important property.
Fish with swim bladder can't switch quickly from the surface layers of water in the deep and back. Therefore, the fish, making a quick vertical movement (tuna, mackerel), is also deprived of the bladder.
No swim bladder and the sharks. So they have to constantly be in motion, so as not to drown. Once they slow down, they immediately begin to sink. So sharks living in the water column, continuously moving even during rest. The sand shark is a substitute bladder bony fishes: they swallow air bubbles and keep it in a special air pocket of the stomach.
Why do fish need a swim bladder?