|Scientific name||Lamna ditropis||Weight||220kg (485 lbs)|
|Pronunciation||sa-muhn shaark||Length||2 to 2.6 meters (6.6 to 8.6 feet)|
|Classification||Chondrichthyes, Lamniformes, & Lamnidae||Location||Northern Pacific Ocean|
The Salmon Shark
It’s not every time you get to meet an animal named after its favorite meal.
Like the honey badger or dung beetles, the salmon shark is another example of an animal that loves a type of food so much that it has been named after it.
The primary food of the salmon shark is the Pacific salmon.
But it also eats squids, sablefish, and herring.
It is one of the apex predators of the Pacific Ocean and an opportunistic feeder with a very diverse diet.
The salmon shark is related to the white shark and is often mistaken for the great white shark because of the similarities in their appearance.
In this article, we’ll explore some of the fascinating facts about the salmon shark, its unique attributes, and its significance to the marine ecosystem where it lives.
Taxonomy and Classification
Lamna ditropis is the scientific name of the salmon shark.
It is sometimes referred to as the Pacific porbeagle or mini great white because it is closely related to these other mackerel shark species.
The closest relative of the salmon shark is the porbeagle (Lamna nasus).
They’re both species of the Lamna genus.
But while the porbeagle’s range is limited to the North Atlantic, the salmon shark lives in the North Pacific.
The salmon shark is a member of the Lamnidae family, a group of predatory sharks also commonly known as white sharks.
The family includes some of the ocean’s most fearsome predators, such as the famous great white shark (Carcharodon carcharias), the shortfin mako (Isurus oxyrinchus), and the longfin mako shark (Isurus paucus).
The salmon shark is relatively large.
It looks very similar to the great white shark, which is why both sharks are often mistaken for each other.
However, the salmon shark’s color slightly differs from the great white’s.
It has a dark gray to black coloration on most of its upper body, while the underside is paler.
The underside also has dark blotches, which aren’t present in other white sharks.
Like other mackerel sharks, the salmon shark has a pointed cone-shaped snout, a streamlined spindle-shaped body, and large gill openings.
The salmon shark generally grows to an average length of about 2.0 to 2.6 meters (6.6–8.6 feet), while the average weight of this shark species is about 220 kilograms (485 pounds).
They exhibit sexual dimorphism, with females slightly bigger than males.
The maximum confirmed length for this shark species is three meters (10 feet), while the maximum reported weight is about 660 pounds.
One of the most distinctive features of this shark is its wide tail which has a double keel (a second ridge runs along the upper lower lobe of this shark’s tail).
This is an unusual feature among sharks, and the only other shark species with a double keel is the porbeagle shark, a close relative of the salmon shark.
The top and bottom jaws of this shark are lined with long rows of small pointed teeth effective for gripping prey and tearing through flesh.
Their eyes are forward-placed, which is typical of predatory shark species.
Habitat and Distribution
The salmon shark primarily lives in the cold and temperate waters of the Pacific Ocean.
The preferred temperature range of the shark is from 2.5 to 24 degrees Celsius.
It is commonly found in coastal and pelagic regions, especially in areas where its preferred prey (salmon) migrate.
One of the most notable ecosystems the salmon shark frequents is the North Pacific Ocean’s eastern boundary, where nutrient-rich waters create a fertile environment for various marine life, including salmon populations.
Salmon sharks can be found along the western coast of North America, from the Bering Sea down to California.
It also lives off the coasts of Alaska, British Columbia, Washington, Oregon, and Northern California.
In the western North Pacific, the salmon shark ranges around the Kamchatka Peninsula and the Sea of Okhotsk.
The seas surrounding Japan also host populations of salmon sharks, especially in the northern regions.
Salmon sharks are typically found in both open seas and coastal waters.
They swim anywhere from the surface to as deep as 668 meters (2,192 feet) below the surface.
Males and females live separately for most of the year.
But they both migrate to the Gulf of Alaska or the coast of Japan to mate during summer or fall every year.
Behavior and Social Structure
Salmon sharks are true ocean wanderers.
The species is known for its extensive migration patterns, which closely follow the movement of salmon populations.
They also migrate for mating purposes and to birth their young in the same locations every year.
The migration pattern of the salmon shark follows specific established routes every year.
Salmon sharks are generally solitary predators.
Although they sometimes swim in school, there’s no evidence that they form stable social groups or hierarchies.
They are more likely to interact with each other during mating events or when multiple individuals are attracted to the same abundant food source, such as during a salmon run.
About 30 to 40 adult salmons may congregate to hunt prey during huge salmon runs.
During these interactions, aggression can occur as individuals compete for access to food.
However, these interactions are often brief and do not result in the formation of long-term social bonds.
Salmon shark populations tend to be segregated by sex and gender.
Males are commonly found in the Western North Pacific, while females live in the Eastern North Pacific.
They only form mixed groups during mating seasons, specifically in summer or autumn.
Salmon shark populations are also segregated by size.
Larger sharks are mostly found in the northernmost reaches of their range, while the smaller sharks stay in the southern region.
The larger, mature sharks are also the only ones that participate in their yearly migrations.
Diet and Feeding
As an apex predator in the Pacific Ocean, the salmon shark is an opportunistic feeder capable of hunting and killing a wide variety of prey in its habitat.
The salmon shark’s diet includes squid, herring, sablefish, walleye pollock, and other varieties of fish.
They have also been observed hunting marine mammals such as sea otters and even some marine birds.
But as their name implies, the major prey of the salmon shark is salmon.
This forms the bulk of their diet and influences their migratory pattern.
Salmon sharks are considered the main predator of Pacific salmon.
However, this may not be true for all populations of salmon sharks.
For instance, salmon sharks in the western North Pacific tend to have a higher concentration in a region south of the typical migration path of the salmons.
Instead, they tend to follow schools of herrings and sardines which form the bulk of their diet.
The shark’s powerful muscles, streamlined body, and specialized hunting techniques are well-suited to capturing these fast and agile fish.
The salmon shark’s jaw is lined with fairly large blade-like teeth.
Each tooth has small bumps (also known as lateral cusplets), which form a kind of “mini teeth” on either side.
The salmon shark employs a variety of hunting strategies to capture its prey.
One of its notable techniques is the “yo-yo diving” approach, where it performs rapid dives and ascents through the water column to ambush unsuspecting prey.
This strategy which is also seen in other predatory sharks, takes advantage of the shark’s speed and agility, allowing it to surprise and catch its prey off guard.
Reproduction and Life Cycle
Adult salmon sharks spend the summer in the northern part of their range.
Towards the end of the summer season, they begin their yearly migratory journey to the south to breed.
Salmon sharks in the western North Pacific tend to migrate to the waters of the Japanese coast to mate.
Populations on the eastern North Pacific breed off the coast of California and Oregon.
Only mature adults make this yearly migratory journey.
The males are typically ready to mate when they’re five, while females start reproducing between eight and ten years.
They congregate in their typical mating grounds in late summer or early autumn.
Like other shark species, male salmon sharks bite the female to hold on to her while copulating.
Fertilization is internal, and the fetus develops internally too.
Salmon sharks are ovoviviparous.
This means they give birth to live young that develop in eggs carried inside the mother’s body.
Unlike placental mammals, where the young take nutrition from their mother, developing embryos consume unfertilized eggs in the mother’s womb.
They have a gestation period lasting at least nine months, after which they give birth to four to five pups.
The pups are typically born in nurseries in late spring.
The nurseries are usually located in the southern end of their range.
Salmon shark females in the western North Pacific return to Japanese waters to give birth to their young in the open oceans, away from predators.
Eastern populations do the same north-south migration, and the young are born in the waters of Oregon and California.
The sharks become independent immediately after birth.
They are capable of hunting for themselves, feeding on small fish and marine invertebrates in their ecosystem.
Ecological Role and Interactions
As a top marine predator, the salmon shark plays a crucial role in regulating the populations of different prey species in its ecosystem.
Salmon sharks prey on various salmon species, which form the bulk of their diet.
A study carried out in 1998 found that Alaskan salmon sharks consumed between 12 and 25% of the total annual run of Pacific salmon in Prince William Sound, Alaska.
By preying on migrating salmon, the salmon shark helps to keep their population under control.
This has a cascading effect on the entire ecosystem as it prevents the overgrazing of food sources which can cause significant ecological imbalances.
Controlling the salmon populations like this influences the abundance and distribution of other species within the marine food web.
As apex predators, adult salmon sharks have very few natural enemies in their ecosystem.
However, young salmon sharks may be killed by larger predators in their ecosystem.
There is no direct evidence of symbiotic relationships between the salmon shark and other species in its ecosystem.
However, indirect interactions are likely to exist.
For instance, smaller predator fish species may travel with salmon sharks and feed on carcasses left behind by their feeding activities.
Conservation Status and Threats
The salmon shark is listed as a species of Least Concern by the International Union for Conservation of Nature (IUCN).
This means it is not considered endangered or threatened.
Commercial fisheries do not actively fish for salmon sharks.
However, the fish is often caught incidentally in trawl nets, troll gear, and other commercial fishery gear.
Commercial fishers consider this fish a pest because of the damage it does to their feeding gear.
Consequently, the salmon shark is often killed and discarded when caught.
Although the population of this shark species is generally stable, commercial fishing is banned in some places, such as Alaska.
Recreational fishing is also heavily regulated.
The major threat to this species is the risk of getting caught as bycatch by commercial fisheries.
The salmon’s shark low rate of reproduction further puts it at risk.
Each female produces just four to five pups every two years.
This means the species probably cannot sustain fishing pressures for extended periods.
Also, reports of juveniles getting stranded on the Pacific coast of the United States have become more frequent than they used to be.
Although the exact cause of this isn’t known, experts think it might be linked to human development, commercial fishing, and other activities in coastal waters where the nursery of this species is located.
Unique Adaptations and Survival Strategies
Like other members of the mackerel shark family, the salmon shark exhibits Homeothermy, which is the ability to regulate its body temperature.
Most fish species are ectotherms, meaning their internal temperature is often the same as the temperature of the surrounding water.
Salmon sharks and other white sharks can keep their body temperature above that of their immediate surroundings thanks to the possession of a vascular heat exchanger known as retia mirabilia.
This is a network of closely-linked arteries and veins usually located in the shark’s cranium, near its eyes.
The structure of this network of blood vessels ensures that the cold blood coming from the gills flows close to blood vessels carrying blood that have been warmed by the body’s metabolic activities.
Consequently, there’s an exchange of heat which ensures that the blood getting to the gills is almost at the same temperature as the surrounding.
This prevents heat loss in this fish.
The salmon shark has the most advanced thermoregulatory ability of all mackerel sharks.
This allows it to maintain an internal temperature higher than the ambient water temperature.
Internal body temperatures as high as 60.1°F (15.6°C) have been recorded in some salmon sharks, which is greater than the surface temperature of the sea where these sharks live.
This ability to maintain stable internal temperature allows the shark to extend its range into areas where other marine predators cannot go in search of food.
In addition, the salmon shark has other adaptations that make it an effective predator species.
The salmon shark’s streamlined body shape and the powerful muscles in its tail allow it to achieve bursts of speed necessary for hunting fast prey like salmon.
The salmon shark also exhibits an adaptive form of camouflage known as countershading.
The upper body has a dark color, while the ventral side is white.
This is an adaptation common in various predator fish species that helps them to blend better with their environment, whether they’re being viewed from above or below.
Cultural Significance and Human Interactions
Salmon shark is recognized in various regions where it is found as an integral part of the marine ecosystem.
Attacks on humans have never been documented, but the similarity in their appearance means they’re often mistaken for great white sharks and mako sharks.
Salmon sharks are considered a menace by commercial fishing boats because of the damage they do to fishing nets and other gear.
So while they’re not often targeted by commercial fisheries, they’re often killed and discarded when caught as bycatch.
Some recreational fishermen also target salmon sharks specifically.
They’re sometimes hunted for food in places like China, Japan, and Alaska.
The fin of the salmon shark is commonly used for making shark fin soup, a traditional Chinese delicacy.
The heart is also used for making Japanese sashimi.
Other parts of this shark’s body, such as the oil and skin (leather), are considered useful in some cultures.
Future Prospects and Research
Currently, not a lot is known about the salmon shark.
It is not considered an endangered species, so it hasn’t been of considerable interest to conservationists.
Recent advancement in tracking technologies has made it possible for marine biologists to tag and track several fish species, including salmon sharks.
This will potentially contribute to a more comprehensive knowledge of this fish in the near future.
As an important apex predator whose distribution contributes to the population of other fish species (especially salmon), understanding the migratory pattern, feeding behaviors, and habitat preferences of this shark species is important.
These scientific findings will be quite valuable in designing effective conservation strategies, creating designated protection areas, and safeguarding the species in the future.
Lamna ditropis, commonly known as the salmon shark, is a species of mackerel shark that lives in the Northern Pacific Ocean.
It is a close relative of the porbeagle shark and also related to the great white shark.
This shark is often mistaken for these other predators but has several unique physical and behavioral attributes.
The salmon shark is an apex predator that hunts different types of marine animals.
The major prey of this species is salmon, and its migratory habits follow schools of this fish as they migrate across the Northern Pacific Ocean.
Lamna ditropis populations also migrate across various ecosystems to mate and give birth to their young.
The massive size of these sharks means they’re potentially dangerous to humans.
However, encounters with humans are rare.
There are no active commercial fisheries targeting this shark species, but it is often caught as a by-catch.