The Salmon Shark (Lamna ditropis) is a species of mackerel shark from the northern Pacific ocean. As an apex predator, the salmon shark feeds on salmon, squid, sablefish, and herring. It is known for its ability to maintain stomach temperature (homeothermy), which is unusual among fish. This shark has not been demonstrated to maintain a constant body temperature. It is also known for an unexplained variability in the sex ratio between eastern and western populations in the northern Pacific.
Unlike most fish, the salmon shark is able to regulate its body temperature due to several different heat-exchange systems in its blood. The shark's name comes from its diet of salmon, particularly during the famed salmon run, but also consists of other fish such as herring, mackerel, sardines, smelt, sablefish, pollock, capelin, rockfish, codfish, and other sharks, as well as squid, octopuses, sea mammals (including large whales), and even sea birds. They have additionally been observed scavenging on the carcasses of whales and other large marine mammals.