The salmon shark Lamna ditropis.
© Dietmar Weber / Shark Foundation
|English: ||Salmon shark, Pacific porbeagle
|French: ||Requin-taupe saumon
|Spanish: ||Marrajo salmon
The biology of the salmon shark (Lamna ditropis)
The salmon shark is a commonly found species which can live both in
coastal and oceanic regions, preferring cool, northern waters. Like
several other species from the Lamnidae family, they can maintain
their body temperature with the help of a vascular net (rete
mirabilis) which maintains the water temperature around their bodies.
They swim both underneath the water's surface and in depths of up to
150 meters. This species is found solitary or in schools and
aggregate when feeding.
The salmon shark has a spinal-shaped, lightly bulbous body with
conspicuously large gill slits and a conical snout. The first dorsal
fin is very high and erect, originating just over or slightly behind
the pectoral insertions. Their second dorsal fin is minute and
begins just about over the beginning of the anal fin. They have
strong keels on the caudal peduncle, with a secondary keel on the
caudal base, and a crescent-shaped dorsal fin.
The salmon shark has a dark gray back and a white belly. The
coloring changes on the sides and is marked by dark spots and
blotches. The first dorsal fin is dark up to its free rear tip.
Salmon sharks are found in the northern and eastern Pacific around
Japan and Korea. Their range stretches from the Bering Strait to
southern California, and they may even venture to Baja California
Salmon frequently gather at the mouth of a river before swimming
upstream to spawn. This periodical accumulation of salmon regularly
attracts larger numbers of salmon sharks into regions of North
Their average size is between 250 and 280 cm long, with a maximum
size of about 300 cm.
As their name implies, salmon shark prefer to feed on Pacific salmon
(from the Oncorhynchus family), but their diet also includes other
The salmon shark reproduces aplacental viviparously (ovoviviparous).
Cannibalism in the uterus is common with this species, i.e. the
embryos in the uterus eat the less developed eggs. Generally salmon
shark bear up to four pups per litter. Males mature when reaching a
length of approximately 180 to 240 cm.
Salmon sharks could be mistaken for mackerel sharks (Lamna nasus),
however, clear identification is possible by comparing the free ends
of their first dorsal fins. With the salmon shark it is just as dark
as the dorsal fin, with mackerel sharks it is white and shows a
clear dividing line.
As with other species from the Lamnidae family, salmon sharks could
be potentially dangerous due to their size.
It is not certain as to what extent the salmon shark must be
considered an endangered species. However, their populations could
be threatened because they are fished by Japanese longline fishermen
in the northern Pacific.
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