| Narrownose smooth-hound | |
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Carcharhiniformes |
| Family: | Triakidae |
| Genus: | Mustelus |
| Species: | M. schmitti |
| Binomial name | |
| Mustelus schmitti S. Springer, 1939 | |
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The narrownose smooth-hound (Mustelus schmitti) is a species of houndshark in the family Triakidae.
With similar morphology amongst 30 other species in the genus, it can be difficult to distinguish Mustelus schmitti from other Mustelus species. Mustelus canis is most mistaken with M. schmitti. However, M. schmitti can be identified through critical aspects of morphology. M. schmitti has gray coloration and spots on the top side of its body and a lighter gray coloration on the bottom side of its body. [2] In addition to coloration, M. schmitti has two dorsal fins, the first dorsal fin (on the anterior side of the body) being more prominent than the second dorsal fin (on the posterior side), both of which have exposed ceratotrichia. The exposed ceratotrichia, which are filaments of collagen creating the fin shape, cause the appearance of a thin, dark band on the dorsal fins on their posterior margins. [2] Alongside the dorsal fins, M. schmitti also has pectoral fins, pelvic fins, an anal fin, and a heterocercal caudal fin (the top caudal fin lobe is larger than the bottom lobe). All its fins are round and broad. The total length of M. schmitti can vary across their distribution. M. schmitti found in Argentina showed longer body lengths than individuals closer to Uruguay. [3] Although M. schmitti can reach between 300 mm to 810 mm in coastal areas with the highest recorded total length documented as 1100 mm. [4] Furthermore, M. schmitti has an inferior mouth with homodont dentition, which refers to the similarity in shape across all the teeth. [5]
M. schmitti is endemic to the southwestern Atlantic Ocean coast. More specifically, M. schmitti is found on the continental shelves of the subtropical south-western Atlantic Ocean, from southern Brazil to northern Argentina, between latitudes 30° S and 44° S, at depths between 60 m to 195 m. M. schmitti has shown ontogenetic habitat preference with distributions differing between age classes of juveniles and neonates, and the adults.
For adults, the distributional changes occur due to a combination of sex segregation, migratory patterns, and the environment. [6] During winter, both males and females will move to warmer water, traveling to southern Brazil. [7] As spring and summer approach, however, adults will move towards the water near Uruguay. [7] Additionally, females will reside in shallow water to engage in birth or intercourse. [7] Larger-sized individuals, often associated with adults, reside in areas that have a higher concentration of salinity and lower depths. [6]
Juvenile and neonate distribution is particularly dependent on environmental factors. Juvenile and neonate distribution does not show much change throughout the year. [6] Typically, they remain near the shore and in warmer water. This is due to a higher abundance of resources, which aids in their growth and development into sexual maturity. [6] Thus, as they reach maturity, they will distribute away from inshore, coastal areas. [6]
As a shark, M. schmitti is classified as a Chondrichthyan, which are most often characterized by sex segregation. Sexual segregation refers to the concept where males and females live in different areas when it is nonreproductive season. Females reside at different depths and temperature of water than males during this period. The pattern of depth and temperature differs with populations living in different areas. M. schmitti females living near El Rincón tend to reside in higher depths and warner water than males during the nonreproductive season. [6] Females in Río de la Plata live at lower depths and colder water during nonreproductive season. [6]
Similar to other species within the same class, M. schmitti tends to have a slow growth rate and long lifespan. [4] The exact age of M. schmitti is difficult to determine, however, general estimations can be made, thus classifications will be made on a basis of juveniles and adults or immature and mature. [8] Determining the growth of an individual often includes the use of the vertebrae. [8] Studies count the number of bands on the vertebra, which will indicate the growth of the individual. [4] This leads to M. schmitti being put in age classes, which are dependent on the total length. The jaw is also a part of this as typically the upper jaw contains more rows of teeth than the lower in adults. [5] Juveniles, however, don’t have much difference between the lower and upper jaws. [5] Adults also tend to have longer teeth, causing a faster replacement rate of teeth. Juveniles, due to the shorter length of their teeth, have a slower replacement rate. [5] To add on, it has been found that females show an average life span of up to 20 years old, whereas males averaged a lifespan of up to 12 years old. [4]
M. schmitti has a late development in sexual maturation like other species within its class. [4] The reproductive cycle is long, with females reproducing only once a year and a gestation period lasting between 10 and 11 months. [3] They are considered ovoviviparous in which females maintain their eggs within their bodies until the embryos develop enough to hatch. [9] [10] This cycle includes migrating toward warmer areas where females can birth litters of one to ten offspring. [3] However, there are occasions in which an observed female will have up to 19 embryos. [3] With their slow reproductive cycle and the tendency to give birth to a small litter, M. schmitti consequently has a low rate of reproduction.
M. schmitti is often described as an “opportunist feeder” due to their diets which include a wide range of prey but are dominated by crustaceans, fish, and polychaetes. Their diets shift as they develop from juveniles to adults but are also impacted by aspects such as geographical distribution and seasonality. In the coastal areas of Río de la Plata, there is a higher consumption of crustacean organisms. [11] The individuals residing in the deeper water of Río de la Plata also feed on crustaceans but consume other organisms as well, primarily fish and polychaetes. [11] In another coastal area located in El Rincón, M. schmitti displayed a preference for polychaetes, while those living in the deep water of El Rincón preferred fish. [11] To add on, the size increase as they develop is also attributed to this shift in their diets. It has been found that diets in coastal areas tend to be abundant in Polychaetes when the sharks are small, typically classified as juveniles. [12] At the same time, as seasons cause a lower temperature, the diets of juveniles become narrow. [11] Prey selection in this area shifts to fish as the sharks’ size increases and moves into deeper water, which is typical in adults. [12] It is suggested that these shifts in diets as individuals age into new life stages are done in attempts to mitigate competition amongst individuals of the same species. [12]
M. schmitti is considered a critically endangered species. [1] This is due to the issue of fishing, both as a victim of bycatch and intentionally through artisanal fishing. [13] Alongside other sharks, M. schmitti is often fished for human consumption. M. schmitti is one of the most caught species in artisanal fishing in the Atlantic coast with small gillnets being the primary method used against them. [14] However, when they are unintentionally caught as bycatch, the specific size of individuals caught is dependent on the size of the gillnets used, which differs across different areas. [15] Fishers will target M. schmitti particularly during the months of April to October. [14] To tackle this issue, specific sized gillnets are promoted to narrow down the portion of the M. schmitti population being caught. [15] Given the migration pattern, reproductive rate, and growth rate, M. schmitti is particularly vulnerable to overexploitation through artisanal fishing and as victims of bycatch. [15]
In addition, M. schmitti has a low level of genetic diversity, further putting the species at risk. [16] M. schmitti has been found to severely lack genetic structure and low nucleotide diversity. [16] While still not fully understood, it is widely hypothesized to be due to a bottleneck event and selection or expansion. [16]
The dusky smooth-hound, also called the smooth dogfish or the dog shark, is a species of houndshark in the family Triakidae. This shark is an olive grey or brown in color, and may have shades of yellow or grayish white. Females live to 16 years and males have a lifespan of 10 years. M. canis was the first shark recognised to have viral infections.
The sand tiger shark, grey/gray nurse shark, spotted ragged-tooth shark, or blue-nurse sand tiger, is a species of shark that inhabits subtropical and temperate waters worldwide. It inhabits the continental shelf, from sandy shorelines and submerged reefs to a depth of around 191 m (627 ft). They dwell in the waters of Japan, Australia, South Africa, and the east coasts of North and South America. The sand tiger shark also inhabited the Mediterranean, however it was last seen there in 2003 and is presumed extinct in the region. Despite its common names, it is not closely related to either the tiger shark or the nurse shark.
The school shark is a houndshark of the family Triakidae, and the only member of the genus Galeorhinus. Common names also include tope, tope shark, snapper shark, and soupfin shark. It is found worldwide in temperate seas at depths down to about 800 m (2,600 ft). It can grow to nearly 2 m long. It feeds both in midwater and near the seabed, and its reproduction is ovoviviparous. This shark is caught in fisheries for its flesh, its fins, and its liver, which has a very high vitamin A content. The IUCN has classified this species as critically endangered in its Red List of Threatened Species.
The smalleye hammerhead, also called the golden hammerhead or curry shark, is a small species of hammerhead shark in the family Sphyrnidae. This species was historically common in the shallow coastal waters of the western Atlantic Ocean, from Venezuela to Uruguay. It favors muddy habitats with poor visibility, reflected by its relatively small eyes. Adult males and juveniles are schooling and generally found apart from the solitary adult females. Typically reaching 1.2–1.3 m (3.9–4.3 ft) in length, this shark has a unique, bright golden color on its head, sides, and fins, which was only scientifically documented in the 1980s. As in all hammerheads, its head is flattened and laterally expanded into a hammer-shaped structure called the cephalofoil, which in this species is wide and long with an arched front margin bearing central and lateral indentations.
Mustelus, also known as the smooth-hounds, is a genus of sharks in the family Triakidae. The name of the genus comes from the Latin word mustela, meaning weasel. It should not be confused with the genus name Mustela, which is used for weasels.
The leopard shark is a species of houndshark, in the family Triakidae. It is found along the Pacific coast of North America, from the U.S. state of Oregon to Mazatlán in Mexico. Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is immediately identifiable by the striking pattern of black saddle-like markings and large spots over its back, from which it derives its common name. Large schools of leopard sharks are a common sight in bays and estuaries, swimming over sandy or muddy flats or rock-strewn areas near kelp beds and reefs. They are most common near the coast, in water less than 4 m (13 ft) deep.
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.
The common smooth-hound is a houndshark of the family Triakidae. It is found in the eastern Atlantic Ocean from the British Isles to South Africa, and in the Mediterranean Sea, Madeira, and the Canary Islands at depths ranging from 5 to 625 m. While they can grow to 200 cm, their usual maximum size is 150 cm. They commonly grow to 100–120 cm with a birth length around 35 cm. The reproduction of commons smooth-hounds is viviparous.
The Izak catshark or simply Izak is a species of shark belonging to the family Pentanchidae, the deepwater catsharks. This species is common off the coasts of South Africa and southern Namibia. It typically inhabits the outer continental shelf at depths of 100–300 m (330–980 ft), with the males found deeper than the females and juveniles. The Izak catshark has a short, wide, flattened head and a robust body tapering to a long, slender tail. It can be identified by its ornate color pattern of dark brown spots or reticulations and blotches on a light yellowish background, as well as by the enlarged dermal denticles over its pectoral fins and along its dorsal midline from the snout to the second dorsal fin. This species reaches 69 cm (27 in) in length, with the males larger than females.
The sharptooth houndshark or spotted gully shark is a species of houndshark in the family Triakidae found in shallow inshore waters from southern Angola to South Africa. Favoring sandy areas near rocky reefs and gullies, it is an active-swimming species that usually stays close to the bottom. This robust shark reaches 1.7 m (5.6 ft) in length and has characteristically large, rounded fins; the pectoral fins in particular are broad and sickle-shaped in adults. It also has a short, blunt snout and long furrows around its mouth. This species is gray or bronze in color above, with variable amounts of black spotting.
The starry smooth-hound is a houndshark of the family Triakidae. It is found on the continental shelves of the northeast Atlantic, between latitudes 61 and 16° N, from the surface to a depth of 200 m (660 ft).
The gray smooth-hound is a houndshark of the family Triakidae. It is spotless and smooth with a narrow head and long blunted snout. This shark is found on continental shelves of the subtropical eastern Pacific. Its range extends from northern California to the Gulf of California, usually residing in waters less than 80 meters deep. Adults are between 0.5 and 1.6 meters long. Furthermore, this shark is viviparous with an egg yolk placenta. Reproduction occurs annually and inland estuaries are common nursery grounds. Although there is little data on the shark’s population trends and catch quantities, the gray smooth-hound is not considered as vulnerable to overfishing. Additionally, there have been three reported sightings of albinism in this species, which is rare for elasmobranchs.
The striped smooth-hound is a houndshark of the family Triakidae, found on the continental shelves of the subtropical southwest Atlantic from southern Brazil to northern Argentina between latitudes 30° S and 47° S, from the surface to 250 m (820 ft). It can grow up to a length of 1.77 m. The reproduction of this shark is Ovoviviparous, with the length at birth up to 39 cm (15 in).
The spotless smooth-hound is a species of houndshark, in the family Triakidae, found on the continental shelves of the northwest Pacific, between latitudes 40° N and 11° N, from the surface to a depth of 300 m. It can grow to a length of up to 1 m.
The brown smooth-hound is a houndshark of the family Triakidae. The reproduction of this shark is viviparous. The brown smooth-hound reaches a maximum reported size of 95.0 cm and a minimum of 27.6cm amongst males while females can range from 25.7 cm to 100 cm although males reach their asymptotic length sooner than females. The average size of this species is between 50 and 70 cm and is between 19 and 21 cm at birth. Females at maternity are around 67.6 cm long whereas the average length at maturity is 63.6 cm for males and 65.6 cm for females. This species is a ground shark and has a heterocercal caudal fin bearing an elongate upper lobe, triangular and broad dorsal fins, broad pectoral fins, an inferior mouth, and large eyes, and displays a reddish or bronze coloration from above and a silverish coloration on the underside. The shark is additionally slender, long-snouted, and sharp-toothed. The teeth of the brown smooth-hound often bear a narrow primary cusp and one or two accessory cusplets.
The starspotted smooth-hound is a houndshark of the family Triakidae. It is a medium-sized shark with irregular white spots across its body. It is found in Northwestern Pacific as well as Kenyan water. This shark mainly inhabits shallow seas and feeds on benthic animals. This shark is ovoviviparous and gives birth to 2-6 larvae per clutch. Currently, due to overfishing, this species is on the edge of extinction.
The speckled smooth-hound is a houndshark of the family Triakidae. It is found on the continental shelf of the eastern Pacific, between latitudes 0° and 54° S, at depths between 16 and 50 m. It can reach a length of 130 cm (51 in). Collectively with certain other species of shark, it is known as "tollo".
The Gulf smooth-hound is a houndshark of the family Triakidae, found on the continental shelves of the tropical western central Atlantic. The reproduction of this houndshark is placental viviparous.
The humpback smooth-hound is a species of houndshark and a part of the family Triakidae. The most noticeable difference between Mustelus whitneyi and its relatives, is the slight curvature, causing a "humpback" appearance located in front of its primary dorsal fin. It is found on the continental shelves of the tropical southeast Pacific, from Peru to southern Chile, between latitudes 3° S and 54° S. These sharks are demersal feeders but range from depths between 15 and 210 metres. Humpback smooth-hound sharks are small sharks, reaching a maximum size of 118 cm (46 in) in total length. Mustelus whitneyi typically feed on teleosts and invertebrates in the benthic and pelagic ecosystems, most important prey being the peruvian anchovy. These humpback smooth-hound sharks are placental viviparious sharks, meaning that the embryo forms inside the mother tethered by the placental cord. The threats currently causing population decline to humpback smooth-hound sharks surround issues with local fisheries and management.
The Australian grey smooth-hound or also known as the grey gummy shark is a species of houndshark classified under the large family Triakidae. It is one of the twenty-eight species belonging to the genus Mustelus, which are often small in length. While members of the genus Mustelus may be found globally in tropical and temperate waters, the grey gummy shark in particular is native to the Pacific Ocean and Indian Ocean waters surrounding Australia and is particularly widespread in deep coastal waters. The grey gummy shark is known to be a viviparous species and gives birth to live young. With little data available, it is regarded to have a relatively stable population and possesses little threat to humans.
| Authority control databases: National |
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