The salmon shark (Lamna ditropis) is a species of mackerel shark found in the northern Pacific ocean. As an apex predator, the salmon shark feeds on salmon, squid, sablefish, and herring. Salmon sharks are known for their ability to maintain stomach temperature (homeothermy), which is unusual among fish. The salmon shark has not been demonstrated to maintain a constant body temperature. The salmon shark is also known for an unexplained variability in the sex ratio between eastern and western populations in the northern Pacific.