Salmon shark (Lamna ditropis)
|Size||Maximum total length: 3.7 m (2)|
Maximum weight: 454 kg (2)
The salmon shark is classified as Least Concern (LC) on the IUCN Red List (1).
A formidable hunter, the salmon shark (Lamna ditropis) is sometimes mistaken for the white shark (Carcharodon carcharias), but can be distinguished by its shorter snout and the dusky blotches that mark the white abdomen of adults (3) (4). The rest of the salmon shark’s stocky, spindle-shaped body is dark bluish-grey or blackish, with white blotches around the base of the pectoral fins. The first dorsal fin is large, while the second dorsal and anal fins are tiny and are able to pivot. Its crescent-shaped tail gives it impressive propulsion through the water (2) (3), while its large, well-developed eyes enable it to spot potential prey (2), and its large, blade-like teeth are well suited to gripping slippery fish (2) (3).
The salmon shark occurs in the North Pacific Ocean. From Japan, North Korea, South Korea and the Pacific coast of Russia, its distribution extends east to the Pacific coast of the U.S.A., Canada, and probably Mexico (3).
The salmon shark is a coastal and oceanic shark, inhabiting waters between 2.5 and 24 degrees Celsius, generally from the surface down to depths around 152 metres, although one individual has been recorded at 255 metres (3).
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).
The salmon shark is often caught as by-catch in Japanese, United States and Canadian fisheries. When caught, often just the fins are taken for shark fin soup and the rest is discarded, although sometimes the flesh may be sold for consumption in Japan and the United States (4). Many fishermen view salmon sharks as pests, as they often damage fishing gear, making them more likely to be killed if captured (4). In addition to the threat of by-catch, some recreational fishing for this shark occurs in Alaskan and Canadian waters (4), and some commercial fishing has taken place in the past, such as in Prince William Sound, Alaska (5).
In 1997, the Alaska Board of Fisheries closed all commercial shark fishing in state waters and implemented strict regulations in the state sports fishery for salmon sharks (4). Measures such as these are vital in protecting this species’ future, until further research can determine the conservation status of this magnificent predator.
Find out more about shark conservation:
Save Our Seas Foundation:
For further information on the salmon shark:
Tagging of Pacific Predators:
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- Anal fins: the unpaired fins on the under surface of a fish, behind the anus.
- By-catch: in the fishing industry, the part of the catch made up of non-target species.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Gestation: the state of being pregnant; the period from conception to birth.
- Ovoviviparous: ovovivipary is a method of reproduction whereby the egg shell is weakly formed and young hatch inside the female; they are nourished by their yolk sac and then ‘born’ live.
- Pectoral fins: in fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
IUCN Red List (April, 2011)
ReefQuest Centre for Shark Research (June, 2008)
Compagno, L.J.V. (2001) Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. Vol. 2: Bullhead, Mackerel and Carpet Sharks (Heterodontformes, Lamniformes and Orectolobiformes). Food and Agriculture Organization of the United Nations, Rome. Available at:
Salmon Shark Biological Profile, Ichthyology Department, Florida Museum of Natural History (June, 2008)
Conservation Science Institute (June, 2008)