This recovery was accompanied by a decline of capelin and cod stocks. Adult cod primarily feed on fish such as capelin and herring. There are also fossils of oceanic fish such as capelin. Some fed on a mixture of capelin and cod, while others had only consumed cod. Examples of migratory forage fish are herring, anchovies, capelin, and menhaden. Other spawning animals which are semelparous include mayflies, squid, octopus, smelt, capelin and some amphibians. Identified fish prey include hake, herring, lantern fish, capelin, pollock, and mackerel. They feed mostly on small pelagic schooling fish, particularly herring, capelin, and sprat. Its favourite prey were fish, including Atlantic menhaden and capelin, and crustaceans. Larger capelin also eat krill and other crustaceans. Fish species include Atlantic cod, swordfish, haddock and capelin; shellfish include scallop and lobster. Some of their prey include herring, mackerel, and capelin. Around Iceland maturing capelin make large northward feeding migrations in spring and summer. The majority of capelin are three or four years old when they spawn. The zooplankton feeders include young cod, capelin, polar cod, whales, and little auk.