Tuna can't stop swimming because over time their gills have evolved differently from those of other fish. The function of their gills has been seriously degraded. If they want to get a lot of oxygen, they need to keep swimming and opening their mouths, so that a lot of water can flow through their mouths into their gills, and then provide oxygen for themselves.

Tuna may suffocate and die if they stop moving. So under normal circumstances, tuna will not stop swimming. Because of their great demand for oxygen, the tuna caught will die as soon as it comes ashore.

Tuna swims while sleeping. As mentioned above, tuna needs to swim constantly to ensure that it can get oxygen. Usually, other fish sleep in a fixed position, with only the gills open and closed to breathe. But tuna need to keep swimming even when they sleep. Although tuna swim while sleeping, their swimming speed will decrease, and their metabolic speed will also decrease at this time.

In addition, tuna don't sleep for too long, and they will wake up after a short rest. In addition, tuna has slowed down when sleeping, so there is no danger in general.