Salmon shark Temporal range: [1] | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Order: | Lamniformes |
Family: | Lamnidae |
Genus: | Lamna |
Species: | L. ditropis |
Binomial name | |
Lamna ditropis C. L. Hubbs & Follett, 1947 | |
Range of the salmon shark |
The salmon shark (Lamna ditropis) is a species of mackerel shark found in the northern Pacific ocean. Similar to other mackerel sharks, salmon sharks have a thunniform body type. As an apex predator, the salmon shark feeds on salmon, squid, sablefish, sea otters, birds, walleye pollock, and herring. [3] Salmon sharks get their name from their diet, which primarily consists of salmon. It is known for its ability to maintain stomach temperature (homeothermy), [4] which is unusual among fish. This shark has not been demonstrated to maintain a constant body temperature. It is also known for an unexplained variability in the sex ratio between eastern and western populations in the northern Pacific. [5]
Adult salmon sharks are medium grey to black over most of the body, with a white underside with darker blotches. Juveniles are similar in appearance, but generally lack blotches. The snout is short and cone-shaped, and the overall appearance is similar to a small great white shark. The eyes are positioned well forward, enabling binocular vision to accurately locate prey. [6]
The salmon shark generally grows to between 200 and 260 cm (6.6–8.6 ft) in length and weighs up to 220 kg (485 lb). [7] Males appear to reach a maximum size slightly smaller than females. Unconfirmed reports exist of salmon sharks reaching as much as 4.3 m (14.2 ft); however, the largest confirmed reports indicate a maximum total length of about 3.0 m (10 ft). [5] The claims of maximum reported weight over 450 kg (992 lb) are "unsubstantiated". [5] [7]
Salmon sharks have a wide, double keeled tail (a second, short ridge that runs along the upper part of the lower lobe of the tail.) The only other shark with a double keeled tail is the porbeagle shark, which the salmon shark is closely related to. Salmon sharks are voracious group hunters. Groups of 30 to 40 individuals have been spotted hunting salmon in Alaska. Salmon sharks can also hunt alone, however individuals congregate in large groups in coastal waters to hunt bony fish such as salmon. Studies on prey consumption show that salmon sharks have similar energetic requirements as sea lions and other piscivorous marine animals. [8]
The salmon shark is ovoviviparous, birthing a litter of two to six pups. [9] As with other lamniforme shark species, the salmon shark is also oophagous, with embryos feeding on the ova produced by the mother.
Females reach sexual maturity from eight to ten years; males generally mature by age five. [10] Reproductive timing is not well understood, but it is believed the sharks are on a two-year cycle, with mating occurring in the late summer to early autumn. [5] Gestation is around nine months. Some reports indicate the sex ratio at birth may be 2.2 (males to females), but the prevalence of this is not known. [5] Once salmon sharks are born, they are completely independent. Pups are spawned along Baja California. [11]
As with only a few other species of fish, salmon sharks have the ability to regulate their body temperature. [4] This is accomplished by vascular counter-current heat exchangers, known as retia mirabilia, Latin for "wonderful nets". Arteries and veins are in extremely close proximity to each other, resulting in heat exchange. 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.
Past studies have shown that the average surface body temperature for the Salmon shark is around 8°C, while the internal average body temperature was around 16–19°C relative to other sharks. [12]
Their homeothermy may also rely on SERCA2 and ryanodine receptor 2 protein expression, which may have a cardioprotective effect. [13]
North of the equator, in the northern Pacific Ocean, the salmon shark is relatively common in continental offshore waters, where it ranges from inshore to just off the coast. Tagging has revealed a range which includes sub-Arctic to subtropical waters. [13] The species is believed to range as far south as the Sea of Japan and as far north as 65°N in Alaska, notably appearing en masse in Prince William Sound during the annual salmon run. Individuals have been observed diving as deep as 668 m (2,192 ft), [14] but they are believed to spend most of their time in epipelagic waters. While salmon sharks primarily travel alone, or in feeding aggregations of several individuals, sometimes they may be seen in schools. According to a study in 2008, salmon sharks have been observed to use area restricted search behaviors in both southern and northern Pacific Ocean regions. Individuals that migrate through southern high productivity regions exhibit more of these behaviors than those who travel through low productivity regions. Salmon sharks travel fast during migratory patterns. Studies conducted on said migrations put the average speed of individual sharks at 33 km. Juvenile salmon sharks stick to more coastal regions along the west coast of North America. Juveniles prefer water temperatures between 12 and 16°C. Juveniles prey on a variety of mesopelagic (intermediate depth) and epipelagic (the upper layer of the water column where light penetrates for photosynthesis) offshore prey. [15]
Age and sex composition differences have been observed between populations in the eastern and western North Pacific. Eastern populations are dominated by females, while the western populations are predominantly male. [7] Whether these distinctions stem from genetically distinct stocks, or if the segregation occurs as part of their growth and development, is not known. The population differences may be a result of Japanese fishermen harvesting more of the male population; certain Japanese herbalists use salmon shark fins (of males, specifically) in some traditional soups and medicines said to treat various forms of cancer. [16]
Currently, no commercial fishery for salmon shark exists, but they are occasionally caught as bycatch in commercial salmon gillnet fisheries, where they are usually discarded. Commercial fisheries regard salmon sharks as nuisances since they can damage fishing gear [9] and consume portions of the commercial catch. Fishermen deliberately injuring salmon sharks have been reported. [17]
Sport fishermen fish for salmon sharks in Alaska. [18] Alaskan fishing regulations limit the catch of salmon sharks to two per person per year. Sport fishermen are allowed one salmon shark per day from April 1 and ending the following March 31 in British Columbia. [19]
The flesh of the fish is used for human consumption, and in the Japanese city of Kesennuma, Miyagi, the heart is considered a delicacy for use in sashimi. [9]
Although salmon sharks are thought to be capable of injuring humans, few, if any, attacks on humans have been reported, but reports of divers encountering salmon sharks and salmon sharks bumping fishing vessels have been given. [17] These reports, however, may need positive identification of the shark species involved. Salmon sharks have never been positively identified attacking humans and there is no confirmed evidence that salmon sharks have attacked humans.
Declines in the abundance of economically important Chinook salmon in the 2000s may be attributed to increased predation by salmon sharks, based on remote temperature readings from tagged salmon that indicate they have been swallowed by sharks. [20]
Similar to white sharks, salmon sharks have a slow growth and reproduction rate, making them susceptible to overfishing and overexploitation. They are considered least concern, however juvenile salmon sharks are extremely susceptible to temperature changes in coastal waters. This means that further ocean warming can severely impact the species. There are reports of declines in salmon shark populations from Alaskan fishermen. [21]
Salmon is the common name for several commercially important species of euryhaline ray-finned fish from the genera Salmo and Oncorhynchus of the family Salmonidae, native to tributaries of the North Atlantic (Salmo) and North Pacific (Oncorhynchus) basins. Other closely related fish in the same family include trout, char, grayling, whitefish, lenok and taimen, all coldwater fish of the subarctic and cooler temperate regions with some sporadic endorheic populations in Central Asia.
The albacore, known also as the longfin tuna, is a species of tuna of the order Scombriformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct stocks known globally in the Atlantic, Pacific, and Indian oceans, as well as the Mediterranean Sea. The albacore has an elongate, fusiform body with a conical snout, large eyes, and remarkably long pectoral fins. Its body is a deep blue dorsally and shades of silvery white ventrally. Individuals can reach up to 1.4 m in length.
Anotopterus nikparini is a species of fish in the family Anotopteridae, the daggertooths. It is native to the northern Pacific Ocean, where it occurs as far north as the Bering Sea and as far south as Japan and Baja California.
The yellowfin tuna is a species of tuna found in pelagic waters of tropical and subtropical oceans worldwide.
The porbeagle or porbeagle shark is a species of mackerel shark in the family Lamnidae, distributed widely in the cold and temperate marine waters of the North Atlantic and Southern Hemisphere. In the North Pacific, its ecological equivalent is the closely related salmon shark (L. ditropis). It typically reaches 2.5 m (8.2 ft) in length and a weight of 135 kg (298 lb); North Atlantic sharks grow larger than Southern Hemisphere sharks and differ in coloration and aspects of life history. Gray above and white below, the porbeagle has a very stout midsection that tapers towards the long, pointed snout and the narrow base of the tail. It has large pectoral and first dorsal fins, tiny pelvic, second dorsal, and anal fins, and a crescent-shaped caudal fin. The most distinctive features of this species are its three-cusped teeth, the white blotch at the aft base of its first dorsal fin, and the two pairs of lateral keels on its tail.
The Chinook salmon is the largest and most valuable species of Pacific salmon. Its common name is derived from the Chinookan peoples. Other vernacular names for the species include king salmon, Quinnat salmon, Tsumen, spring salmon, chrome hog, Blackmouth, and Tyee salmon. The scientific species name is based on the Russian common name chavycha (чавыча).
The sockeye salmon, also called red salmon, kokanee salmon, blueback salmon, or simply sockeye, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it. This species is a Pacific salmon that is primarily red in hue during spawning. They can grow up to 84 cm in length and weigh 2.3 to 7 kg (5–15 lb). Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to 1,600 km (1,000 mi). Their diet consists primarily of zooplankton. Sockeye salmon are semelparous, dying after they spawn. Some populations, referred to as kokanee, do not migrate to the ocean and live their entire lives in fresh water.
The Atlantic blue marlin is a species of marlin endemic to the Atlantic Ocean. It is closely related to, and usually considered conspecific with, the Indo-Pacific blue marlin, then simply called blue marlin. Some authorities consider both species distinct.
Pink salmon or humpback salmon is a species of euryhaline ray-finned fish in the family Salmonidae. It is the type species of the genus Oncorhynchus, and is the smallest and most abundant of the seven officially recognized species of salmon. The species' scientific name is based on the Russian common name for this species gorbúša (горбуша), which literally means humpie.
The coho salmon is a species of anadromous fish in the salmon family and one of the five Pacific salmon species. Coho salmon are also known as silver salmon and is often sold as medium red salmon. The scientific species name is based on the Russian common name kizhuch (кижуч).
Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs.
The gummy shark, also known as the Australian smooth hound, flake, sweet william or smooth dog-shark, is a species of ground shark in the genus Mustelus of the family Triakidae. These small to medium-sized bottom-dwelling sharks are found mostly in, but are not limited to, the area around the southern seas of Australia and is commonly baited and fished for cuisine because of its taste and market prices. According to a 2021 paper by White, Arunrugstichai & Naylorn (2021), Mustelus walkeri is the same animal as M. antarcticus. One theory is that M. walkeri is a subpopulation of M. antarcticus.
Hippoglossus stenolepis, the Pacific halibut, is a species of righteye flounder. This very large species of flatfish is native to the North Pacific and is fished by commercial fisheries, sport fishers, and subsistence fishers.
The common thresher, also known as Atlantic thresher, is the largest species of thresher shark, family Alopiidae, reaching some 6 m (20 ft) in length. About half of its length consists of the elongated upper lobe of its caudal fin. With a streamlined body, short pointed snout, and modestly sized eyes, the common thresher resembles the pelagic thresher. It can be distinguished from the latter species by the white of its belly extending in a band over the bases of its pectoral fins. The common thresher is distributed worldwide in tropical and temperate waters, though it prefers cooler temperatures. It can be found both close to shore and in the open ocean, from the surface to a depth of 550 m (1,800 ft). It is seasonally migratory and spends summers at lower latitudes.
The Pacific ocean perch, also known as the Pacific rockfish, rose fish, red bream or red perch, is a fish whose range spans across the North Pacific : from southern California around the Pacific rim to northern Honshū, Japan, including the Bering Sea. The species appears to be most abundant in northern British Columbia, the Gulf of Alaska, and the Aleutian Islands.
Lamna is a genus of mackerel sharks in the family Lamnidae, containing two extant species: the porbeagle of the North Atlantic and Southern Hemisphere, and the salmon shark of the North Pacific.
The Gulf grouper is a species of marine ray-finned fish, a grouper from the subfamily Epinephelinae which is part of the family Serranidae, which also includes the anthias and sea basses. It is endemic to Mexico.
The widow rockfish, or brown bomber, is a species of marine ray-finned fish belonging to the subfamily Sebastinae, the rockfishes, part of the family Scorpaenidae. It is found in the northeastern Pacific Ocean.
Lampris guttatus, commonly known as the opah, cravo, moonfish, kingfish, and Jerusalem haddock, is a large, colorful, deep-bodied pelagic lampriform fish belonging to the family Lampridae, which comprises the genus Lampris.
The Pacific spiny dogfish is a common species of the Squalidae (dogfish) family of sharks and are among the most abundant species of sharks in the world. This species is closely related to the Spiny dogfish and for many years they were treated as a single species. Recent research, using meristic, morphological and molecular data led to the resurrection of the Pacific spiny dogfish as a separate species. The American Fisheries Society recommends the common name "Pacific spiny dogfish" for Squalus suckleyi over alternatives such as "spotted spiny dogfish" and "North Pacific spiny dogfish" and "spiny dogfish" for Squalus acanthias.
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