Mackerel

Mackerel are fast swimmers and travel in huge, flashing schools through the open sea. Their back is blue-green with dark wavy stripes and their belly is silver, so they are hard to see from above and below. They have to keep moving almost all the time to get enough oxygen.

For scientists

The Atlantic mackerel (Scomber scombrus) is a fast, schooling open-ocean fish without a swim bladder, which is why it must swim almost constantly to keep from sinking and to drive enough water over its gills. Its tiger stripes and countershading (dark back, pale belly) camouflage it in open water. Mackerel make long seasonal migrations and are an important link between plankton and larger predators.

Source: NOAA

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