Humpback smooth-hound

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Humpback smooth-hound
Mustelus whitneyi SI.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Carcharhiniformes
Family: Triakidae
Genus: Mustelus
Species:
M. whitneyi
Binomial name
Mustelus whitneyi
Mustelus whitneyi distmap.png

The humpback smooth-hound (Mustelus whitneyi) is a species of houndshark and a part of the family Triakidae. [2] 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 (50 and 690 ft). Humpback smooth-hound sharks are small sharks, reaching a maximum size of 118 cm (46 in) in total length. [1] Mustelus whitneyi typically feed on teleosts and invertebrates in the benthic and pelagic ecosystems, most important prey being the peruvian anchovy. [3] These humpback smooth-hound sharks are placental viviparious sharks, meaning that the embryo forms inside the mother tethered by the placental cord. [4] The threats currently causing population decline to humpback smooth-hound sharks surround issues with local fisheries and management.

Contents

Description

The humpback smooth-hound is a small shark growing to a length of up to 68 cm (27 in) in total length for males and 74–87 cm (29–34 in) for females, with a maximum size of 119 cm (47 in). [5] It has a sturdy body with a moderately long, broad, sharply angled snout and large eyes, set widely apart. The mouth is fairly long and the upper lip furrows are longer than the lower ones. The teeth have a main pointed cusp and sometimes smaller subsidiary ones. The first dorsal fin is approximately triangular and the trailing edge is fringed with bare, dark-coloured collagen rods known as ceratotrichia. The pectoral fins are large and the pelvic fins moderately so. The caudal peduncle is short and the lower lobe of the tail fin is hardly curved in adults. The color of this shark is plain grey or greyish-brown without any spots or barring. [6] The main difference between humpback smooth-hounds and others in its family, as mentioned before, is the slight curvature located directly behind the head, causing a "humpback" appearance.

The humpback smooth-hound is streamlined in many different aspects. First being that the humpback smooth-hound has a almost completely cylindrical body allowing the animal to dive through the water. The shape of the primary dorsal fin reduces friction drag in the water, allowing the animal to move without exerting as much energy. Finally, the upper caudal lobe is disproportionately larger than the lower caudal lobe. This allows the shark to quickly and easily change direction.

Distribution and habitat

The humpback smooth-hound is found in the southeastern Pacific Ocean off the coast of Peru and Chile, between 1°N and 45°S. Although, the humpback smooth-hound is found within this range; it is rarely found in Chile, and mainly concentrated in Peru. [7] Its depth range is between 16 and 211 m (50 and 690 ft) but it is most common between 70 and 100 m (230 and 330 ft). [8] Mustelus whitneyi is classified as a shark living in the marine neritic habitat, meaning it can be found in coastal waters. The shark is both a demersal and pelagic feeder, often found in coastal waters at the continental base, near the seabed, or on rocky shores. [1]

Due to their presence in both benthic and pelagic habitats humpback smooth-hounds play an important ecological role in transferring resources between the two. The sharks act as mobile links for nutrients and resources through the methods of predation and waste release. [3]

Biology and ecology

Humpback smooth-hound sharks are placental viviparous sharks, placental meaning that the sharks develop inside the body in a placental sac connected to the mother. The minimum gestation for these sharks was 7 months however gestation is likely to last 10-11 months. The female humpback smooth-hounds then have on average, 10 pups per litter measuring 22–23 cm (8.7–9.1 in) at birth. [4]

Humpback smooth-hound sharks feed on a variety of organisms in both the benthic and pelagic coastal ecosystems. The main components of their diet include: bivalves, cephalopods, gastropods, and teleosts. They might also feed on crustaceans such as crabs and mantis shrimps. A very important prey species of the humpback smooth-hound is the Peruvian anchovy, a small pelagic schooling fish. [3]

The humpback smooth-hound sharks are one of the top predators in their ecosystems therefore they have large ecological impacts. First being that these sharks regulate prey dynamics and populations through predation. Secondly, these sharks modify and influence prey behavior and physiology. Also, the decline in these predators can cause an increase in cephalopod and other prey species biomass. This increase can trigger cascading effects in the pelagic ecosystem. Humpback smooth-hound sharks specifically act as mobile links for resources between the benthic and pelagic environments they in habitat. By the methods of predation, excretion, and defecation the sharks transport nutrients and other resources between these two ecosystems. [3]

Specifically in the benthic habitats Humpback smooth-hounds physically alter the habitat through their predation. Because they prey on mollusks or other infaunal organisms they physically and biologically alter the sediment of the habitat, which can facilitate the penetration of oxygen in sediments and affects the nitrogen cycle. Their method of predation also causes more prey and resources to be accessible for many other species. [3]

Status and threats

The humpback smooth-hound is fished for human consumption in Chile but more particularly in Peru, where it is more common. [1] The Peruvian fisheries are the main threat to the population decline through directly removing these sharks and indirectly through bycatch. The unsustainable harvest causing population decline is shown in the Peruvian gillnet fisheries and the trawl fisheries in Ecuador which the Humpback is mainly caught as bycatch, and discarded. [1] Along with the spotted houndshark (Triakis maculata) and the speckled smooth-hound (Mustelus mento), it is known as "tollo" in its local fisheries, and of the three species it is the humpback smooth-hound that is the main target of the tollo fishery in Peru, [1] which masks the true catch of humpback smooth-hound causing more individuals to be unsustainably removed. [7] Landings averaging 11,000 tons of tollo per year were made in that country between 1965 and 1989, but quantities caught diminished thereafter. [1] A minimum size requirement of 60 cm (24 in) was set in 2001 but was pitched so low as to have limited conservation effect. This is because this requirement does not protect the mature individuals which reproductively contribute to the population size and growth. The humpback smooth-hound is the 4th most captured of all sharks and the most captured of all demersal organisms. [1] The fishery overexploitation is the cause of >80% reduction in population size of humpback smooth-hound sharks. [1] The International Union for Conservation of Nature (IUCN) has rated the status of the humpback smooth-hound as being critically endangered due to overexploitation. [1]

Related Research Articles

<span class="mw-page-title-main">Dusky smooth-hound</span> Species of shark

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.

<span class="mw-page-title-main">School shark</span> Species of 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.

<span class="mw-page-title-main">Pelagic fish</span> Fish in the pelagic zone of ocean waters

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.

<span class="mw-page-title-main">Demersal fish</span> Fish that live and feed on or near the bottom of seas or lakes

Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes. They occupy the sea floors and lake beds, which usually consist of mud, sand, gravel or rocks. In coastal waters, they are found on or near the continental shelf, and in deep waters, they are found on or near the continental slope or along the continental rise. They are not generally found in the deepest waters, such as abyssal depths or on the abyssal plain, but they can be found around seamounts and islands. The word demersal comes from the Latin demergere, which means to sink.

<span class="mw-page-title-main">Smooth-hound</span> Genus of sharks

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.

<span class="mw-page-title-main">Houndshark</span> Family of sharks

The Triakidae or houndsharks are a family of ground sharks, consisting of about 40 species in nine genera. In some classifications, the family is split into two subfamilies, with the genera Mustelus, Scylliogaleus and Triakis in the subfamily Triakinae, and the remainders in the subfamily Galeorhininae.

<span class="mw-page-title-main">Leopard shark</span> Species of shark

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.

<span class="mw-page-title-main">Slender smooth-hound</span> Species of shark

The slender smooth-hound or gollumshark is a species of ground shark in the family Pseudotriakidae. It is endemic to the waters around New Zealand, where it is usually found close to the bottom over the continental slope at depths of 300–600 m (980–1,970 ft). An extremely slim, plain brownish shark reaching 1.1 m (3.6 ft) in length, the slender smooth-hound can be identified by its broad, flattened head with a long, distinctively bell-shaped snout. Its mouth is angular with short furrows at the corners, and contains a very high number of tooth rows in both jaws. Its two dorsal fins are roughly equal in size.

<span class="mw-page-title-main">Spotted houndshark</span> Species of shark

The spotted houndshark is a houndshark of the family Triakidae found in tropical waters in the eastern Pacific Ocean off the coast of South America. It usually grows to a length around 180 centimetres (71 in). The reproduction of this houndshark is ovoviviparous, with a litter of 14 pups being found in one female with a birth size of 30 to 40 centimetres. Their diet is believed to consist mainly of crustaceans.

<span class="mw-page-title-main">Sharptooth houndshark</span> Species of shark

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.

<span class="mw-page-title-main">Starry smooth-hound</span> Species of shark

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<span class="mw-page-title-main">Sharptooth smooth-hound</span> Species of shark

The sharptooth smooth-hound is a houndshark of the family Triakidae. It is found on the continental shelves of the tropical eastern Pacific from southern Mexico to Peru between latitudes 20°N and 5°S. Its length is up to 64 cm.

<span class="mw-page-title-main">Spotless smooth-hound</span> Species of shark

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.

<span class="mw-page-title-main">Speckled smooth-hound</span> Species of shark

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".

<span class="mw-page-title-main">Narrownose smooth-hound</span> Species of shark

The narrownose smooth-hound is a species of houndshark in the family Triakidae. It 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. It can reach a length of 74 centimeters.

<span class="mw-page-title-main">Gulf smooth-hound</span> Species of shark

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<span class="mw-page-title-main">Australian grey smooth-hound</span> Species of shark

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.

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The Cape horse mackerel is a mackerel-like species in the family Carangidae. It is a pelagic species of the south eastern Atlantic Ocean which is a target of fisheries, mainly as bycatch.

<span class="mw-page-title-main">Benthic-pelagic coupling</span> Processes that connect the benthic and pelagic zones of a body of water

Benthic-pelagic coupling are processes that connect the benthic zone and the pelagic zone through the exchange of energy, mass, or nutrients. These processes play a prominent role in both freshwater and marine ecosystems and are influenced by a number of chemical, biological, and physical forces that are crucial to functions from nutrient cycling to energy transfer in food webs.

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References

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