because of the increased water pressure,and most of non-migrating midwaterfishes have lost the swim bladder as an-other energy-saving adaptation. To com-pensate for the loss of the swim bladder,they have developed soft, weak bones andlost defensive structures like spines andscales. These adaptations reduce weightand make them more neutrally buoyant, which allows them to float at a constantdepth without wasting energy swimming.Since they don’t swim much, they haveno need for the streamlining that is socharacteristic of epipelagic fishes