Salmon Shark (Lamna ditropis)

Occurring singly or in schools of several individuals (3), salmon sharks are long distance, high-speed predators (2), occasionally seen at or near the surface in some areas. They can maintain their body temperature well above that of the surrounding cold water of the North Pacific, and may have the highest body temperature of any shark (3). This allows them to maintain warm swimming muscles and internal organs, so they can still hunt effectively in cool waters (2). The salmon shark is considered to be one of the main predators of the Pacific salmon, and its voracious feeding on this fish has earned it its common name (3). However, it is an opportunistic feeder that consumes a wide variety of fish that also includes (amongst many others) herring, sardines, pollock, Alaska cod, lanternfishes and mackerel. It also feeds on some squid and is sometimes attracted to by-catch dumped back into the ocean by shrimp trawlers (3). After spending the summer in the north of their range, the salmon shark migrates south to breed. In the western North Pacific they migrate to Japanese waters whereas in the eastern North Pacific, the salmon shark breeds off the coast of Oregon and California, USA. The young are born in spring after a gestation period of around nine months (3). The salmon shark is ovoviviparous, and oophagy (when the growing embryos eat unfertilized eggs to gain nutrients) has been recorded in this shark (4). Most litters contain between two and five young. Male salmon sharks are thought to mature at about five years and live to at least 27 years; females reach maturity at eight to ten years and are known to live to at least 20 years (3).

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