A Brandt's cormorant in a school of Pacific mackerel beneath an oil rig off the coast of California, USA

A seabird gets ‘schooled’

This deep-diving Brandt’s cormorant appears to be on the hunt for a meal, and there’s plenty of Pacific mackerel to choose from here off the coast of Los Angeles, in the US state of California. While seabirds like the cormorant are a threat to them, these mackerel aren't totally defenceless. Fish have many ways of protecting themselves, including travelling in dense schools like this one. It's a technique which not only allows for speedy travel (because it reduces friction on most of the fish in the school) it also makes it more difficult for predators to pick out an individual victim. For these fish, there's safety in numbers. As Dory, in Finding Nemo, puts it: “Just keep swimming, just keep swimming.”