bitch-dont-krill-my-vibe:

Striped mackerel with mouth wide open.

Photo belongs to Alex Mustard Underwater Photography

This fish seems to have gill rakers, which are structures used a little bit like the baleen of the baleen whales. They swim around with their mouths open, and water goes into their mouth and out their gills. The plankton in the water goes into their mouth, but is caught on the rakers and funneled down the throat rather than going out the gills. It’s kind of like if you attached a mesh funnel around your face and ran around catching flies with it, except that the funnel is also your lungs.

It looks really silly when an entire school of them does this at once.