Salmon Shark

Lamna ditropis

The salmon shark is the North Pacific's cold-water counterpart to the great white — a stocky mackerel shark with the same conical snout and heavy, torpedo-shaped body, though it rarely exceeds 2.6 m and about 220 kg. Adults are dark grey to nearly black above with a white belly broken by dusky blotches; juveniles are plain underneath. Like its relatives it is regionally endothermic: paired counter-current heat exchangers, the retia mirabilia, trap metabolic heat and hold the core near 16-19°C in water around 8°C, which is what lets it hunt fast and accurately in sub-Arctic seas. Its range runs from the Sea of Japan across the North Pacific to Alaskan waters above 65°N. It spends most of its time in the sunlit surface layer but has been tracked as deep as 668 m. Salmon give the shark its name, though it also takes squid, herring, walleye pollock, sablefish and the occasional seabird. Females bear two to six live pups after roughly nine months and mature at eight to ten years; males mature at about five. Divers meet salmon sharks only by chance, typically in cold open water near the summer salmon runs, and no attack on a person has ever been confirmed. The IUCN lists the species as Least Concern.