The Salmon Shark

Let’s talk about it … The Salmon Shark

This blog is going to take us back to the days I first started with African Shark Eco-Charters, Shark Diving Cape Town, when I went on a journey of learning about sharks. All the various species, the largest, the smallest and the most beautiful. Those that fly through the air and those that walk on land, and of course, those that we didn’t even know were sharks. It was a fun journey that spanned about a year and has equipped me with a good general knowledge on sharks. Well, that is what I had originally thought, until I heard of this little guy; the Salmon Shark, apparently also known as the Dwarf White Shark. When I first saw this little guy, I must admit, it was love at first sight. But enough of my waffling, let’s learn some stuff.

Let’s talk about the physical attributes of this gorgeous little creature.

A fully grown Salmon Shark is between 200 and 260cm in length, that is between 6.5 and 8.5ft, and they weight up to about 220kgs (485lb). The female of the species seem to out size the males, as we see in quite a number of shark species. This gorgeous shark is not without its very own unsubstantiated claims, as we know to be true for many of the sharks in the oceans of the world. Claims of this dwarfed Great White, reaching sizes of more than 4.3m (14.2ft) and weighing in at 450kg (992lb). None of these reports have been substantiated and there is absolutely no photographic evidence of this being true, so just another “did you know” but of gossip, or perhaps someone saw what they thought was a Salmon Shark, and it actually turned out to be a Juvenile Great White or even a Thrasher…

The Salmon Shark, has a medium grey to black colour reaching from its dorsal and covering most of its body. The underside is white with darker blotches. The juvenile Salmon Shark does not sport the blotches, but does have the same colouring as the adults, just sans the darker patches. The head and snout is short and cone shaped, with eyes that make me think of a Thrasher Shark, big and round and dewy. Their eyes are situated more forward on the head than that of the Great Whites, so as to assist this little apex predator to locate its prey of salmon, squid, sablefish and herring.

These little beauties are found in the Eastern and Western North Pacific, so they prefer colder waters. Here is an interesting fact about Salmon Sharks; they are able to regulate their stomach temperatures. Most sharks and other fish do not possess this ability, making it quite special and specific to our little fried.

In the eastern North Pacific, the female of the species can live to at least 20 years of age, while the males make it to at least 27 years. Where we might see the maturation of the female gender happening before that of the male in most creatures, in the western North Pacific, male Salmon Sharks mature at about 5.8 to 6.1 ft (177-186 cm) in total length which when equated to years, is around 5 years, and female Salmon Sharks mature at about 6.6 to 7.3 ft (200-223 cm) being approximately 8-10 years.

As mentioned above, the Salmon Shark is known for its ability to maintain stomach temperature, the technical or scientific term for this is “homeothermy” and as stated above, this is unusual among fish. This super ability, has not evolved to the regulation of the entire body or to the maintenance of a constant body temperature, but I think being able to regulate your tummy temp is pretty cool. Another interesting factoid is that the Salmon Shark is known for an unexplained variability in the sex ratio between Eastern and Western populations in the Northern Pacific.

You may be interested in how this amazing “Dwarf Great White”, as it is sometimes affectionately referred to, does this homeothermy thing; that is the ability to maintain gut temperature? Well, it is accomplished by vascular “counter-current heat exchangers, and these are called “retia mirabilia” which in Latin means “wonderful nets”. Makes sense, and one realises just how apt the term is when you understand that this is when arteries and veins are very close to each other, resulting in the heat exchange. It’s a network of arteries and veins. The easiest way to explain this would be; cold blood coming from the gills to the body is warmed by blood coming from the body. This results in blood coming from the body losing its heat so that by the time it interacts with cold water from the gills, it is about the same temperature, so no heat is lost from the body to the water. Blood coming towards the body regains its heat, allowing the shark to maintain its body temperature. This minimizes heat lost to the environment, allowing salmon sharks to thrive in cold waters.

The salmon shark is ovoviviparous, that is to say that she has embryos that develop inside eggs that remain inside the mother’s body until they are ready to hatch. Our little female Salmon Shark has an average litter size of two to six pups. Now remember, a Salmon Shark only reaches sexual maturity at 5 for the males and the females take between 8 to 10 years, so that means that their juvenile status holds for up to a minimum of 5 years.

Salmon Sharks are commonly found in continental offshore waters, but have also been known to range from inshore to just off beach areas. They usually occurs alone when not feeding, but when feeding aggregations there can be several individuals, or they can even occur in schools. This information is gleaned due to various tagging initiatives, which have revealed an area range which includes sub-Arctic to subtropical waters. This shark occurs in the North Pacific Ocean, in both coastal waters and the open ocean and they are believed to spend most of their time in epipelagic water; that is uppermost layer of a body of water, making these little guys, surface feeders, much like their larger cousins, the Great White.

Sadly the population differences may be a result of Japanese fishing specifically the male population of the Salmon Shark. It is believed that the fins of the male of the species holds a cure to various forms of cancer and as a result Japanese herbalists make a compound using these fins.

Other than this fishing of this shark, no commercial fishery for salmon shark exists, as with most other sharks and marine creatures, they are occasionally caught as bycatch in commercial salmon gillnet fisheries, where it is believed they are just discarded. Commercial fisheries consider salmon sharks a nuisances because they damage nets and other fishing gear as well as eating a portion of their commercial catch. It has been reported that fishermen deliberately harm Salmon Sharks.

There is an element of sports fishing of these sharks, and sport fishermen do fish for salmon sharks in Alaska. There are regulations passed by the Alaskan regulatory departments; that sports fishermen are only permitted to fish 2 Salmon Sharks per year. But horrifically in British Columbia, sport fishermen are allowed one salmon shark per day for the entire year.

The flesh of the fish can be and is used for human consumption, and in the Japanese city of Kesennuma Miyagi, the heart of the Salmon Shark is considered a delicacy and is used for sashimi.

Although Salmon Sharks look like little Great Whites and are thought to be capable of injuring humans, few, if any, attacks on humans have ever been reported, but reports of divers encountering salmon sharks and salmon sharks bumping fishing vessels have been given. The validity  of these reports would need to be confirmed as there have been no confirmed and verified recognition of these claims.

Let’s be kind to the world around us, let’s appreciate all the creatures and the part they play in the greater eco-system, each having a very specific role. Let us, as the dominant species, respect that which has been placed I our care, and sustainably source and fish for our food, remembering that there is a whole other eco-system that also needs to survive.

Be kind, and until we meet again, keep that toothy grin.

By Nadine Bentley