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 fo

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.