Why do a fish breathe slower in cool water?

Fish breathe slower in cool water because the amount of dissolved oxygen in water decreases as water temperature decreases.

- Cooler water holds more dissolved oxygen than warmer water, so fish don't need to breathe as often to get the same amount of oxygen.

- Fish metabolism slows down in cool water, so they don't need as much oxygen to power their bodies.

- Fish gills are more efficient at extracting oxygen from cold water than warm water.

All of these factors contribute to the fact that fish breathe slower in cool water.