They are carnivores and primarily feed on small fish such as krill, juvenile salmon, and herring.[1] They are also baleen whales, which means that they do not have teeth,[10] so they must be able to eat things that they can swallow whole. They have several vertical grooves running down the length of their body so that they can hold large volumes of water and fish at one time. They feed for up to twenty-two hours a day, taking in anywhere from 4,400-5,500 pounds of food per day.[6] The only time they feed is during the summer months; in the winter, they live solely off fat reserves that they have stored.[10] They are not able to feed in warmer waters such as Hawaii or Mexico because there is no adequate habitat for the fish that they consume.