Daggernose shark
Encyclopedia
The daggernose shark is a little-known species
of requiem shark
, family
Carcharhinidae, and the only extant member of its genus
. It occurs in shallow tropical waters off northeastern South America
from Trinidad
to northern Brazil
, favoring muddy habitats such as mangrove
s, estuaries, and river mouths, though it is intolerant of fresh water
. A relatively small shark typically reaching 1.5 m (4.9 ft) in length, the daggernose shark is unmistakable for its elongated, flattened, and pointed snout, tiny eyes, and large paddle-shaped pectoral fins.
Daggernose sharks are predators of small schooling fishes. Reproduction is viviparous, with females give birth to 2–8 pups every other year during the rainy season; this species is capable of shifting the timing of its reproductive cycle by several months in response to the environment. Harmless to humans, the daggernose shark is caught for food and as bycatch
in artisanal
and commercial fisheries
. Limited in range and slow-reproducing, it has been assessed as Critically Endangered
by International Union for Conservation of Nature in light of a steep population decline in recent years.
and Friedrich Gustav Jakob Henle
in their 1839 Systematische Beschreibung der Plagiostomen. They chose the specific epithet oxyrhynchus, from the Greek oxys ("sharp" or "pointed") and rhynchos ("nose"). In 1862, American ichthyologist Theodore Gill
coined the genus Isogomphodon for this species, from the Greek isos ("equal"), gomphos ("nail" or "peg"), and odous ("tooth"). However, Isogomphodon was subsequently relegated to being a synonym
of Carcharhinus
, until it was resurrected by shark authority Stewart Springer
in 1950. Regardless of its taxonomic validity, Isogomphodon, along with the genera Nasolamia and Prionace, is closely related to Carcharhinus. An extinct relative, I. acuarius, dates back to the Middle Eocene (45 Ma).
, off Trinidad
, Guyana
, Suriname
, French Guyana, and northern Brazil
. It reportedly occurs as far south as Valença
in the central Brazilian state of Bahia
, though fishery
surveys have not detected this species in the area and it is apparently unknown to local fishermen.
An inhabitant of coastal waters at a depth of 4–40 m (13.1–131.2 ft), the daggernose shark prefers highly turbid waters and decreases in number with increasing water clarity. Females tend to be found at greater depths than males. Its range encompasses a wide continental shelf
with a humid tropical climate
, extensive mangrove
s, and draining by numerous rivers including the Amazon
. Water salinity
in this area ranges from 20 to 34 ppt, while the tidal amplitude
can measure up to 7 m (23 ft). Daggernose sharks are most common over shallow muddy banks and in estuaries
and river mouths. It seems to be intolerant of low salinity, moving inshore during the dry season
(June to November) and offshore during the rainy season (December to May). This species is not known to make long-distance movements, though some local seasonal movements are possible.
suggests, the daggernose shark has a very long, flattened snout with a pointed tip and an acutely triangular profile from above. The eyes are circular and minute in size, with nictitating membrane
s (a protective third eyelid
). The nostril
s are small, without prominent nasal skin flaps. There are short but deep furrows at the corners of the mouth on both jaws. The tooth rows number 49–60 and 49–56 in the upper and lower jaws respectively. Each tooth has a single narrow, upright cusp; the upper teeth are slightly broader and flatter than the lower teeth, with serrated rather than smooth edges.
The body is robustly built, with large, broad, paddle-like pectoral fins that originate under the fifth gill slit
. The first dorsal fin
originates over the posterior half of the pectoral fin bases. The second dorsal fin is about half as tall as the first and located over or slightly ahead of the anal fin. The anal fin is smaller than the second dorsal fin and has a deep notch in the rear margin. The caudal fin has a well-developed lower lobe and is preceded by a crescent-shaped notch on the upper side of the caudal peduncle. The coloration is a plain gray above, sometimes with a brownish or yellowish cast, and lighter below. Males attain a length of 1.4 m (4.6 ft) and females 1.6 m (5.2 ft). There are unsubstantiated records of individuals 2–2.4 m (6.6–7.9 ft) long. The maximum known weight is 13 kg (28.7 lb).
(Carcharhinus porosus) and the bonnethead
(Sphyrna tiburo). Its elongated snout and tiny eyes are likely consequences of living in murky sediment-laden waters, reflecting an adaptive
emphasis on electroreception
and other rostral
senses rather than vision. The snout bears a superficial similarity to the goblin shark
(Mitsukurina owstoni), some Apristurus
catshark
s, and the long-nosed chimaeras
, all found in the deep sea
. With long jaws and numerous small teeth, the daggernose shark is well-suited for capturing the small schooling fishes that comprise most of its diet. Known prey taken include herring
, anchovies
, catfish
, and croakers
.
The daggernose shark is viviparous; once the developing embryo
s exhaust their supply of yolk, the depleted yolk sac
is converted into a placenta
l connection through which the mother delivers sustenance. Females give birth to litters of 2–8 pups every other year, following a year-long gestation period
. There is no correlation between female size and number of offspring. Mating
and parturition take place over a roughly six-month period from the beginning to the end of the rainy season. However, the daggernose shark is capable of shifting the timing of its reproductive cycle by at least four months, possibly in response to varying environmental conditions. Females move into shallow coastal nurseries to give birth; one important nursery exists off Brazilian state of Maranhão
.
Newly born daggernose sharks measure 38–43 cm (15–16.9 in) in length. Males mature at 103 cm (40.6 in) long, corresponding to an age of 5–6 years, while females mature at 115 cm (45.3 in) long, corresponding to an age of 6–7 years. The lifespan
of males has been measured at up to 7 years, and females 12 years; extrapolating from growth rates suggest that the largest known males and females may be 12 and 20 years old respectively.
in Trinidad, Guyana, Suriname, and French Guyana. It also comprises about one-tenth of the catch of a northern Brazil floating gillnet
fishery targeting Serra Spanish mackerel
(Scomberomorus brasiliensis) and Acoupa weakfish
(Cynoscion acoupa), which operates in estuaries during the dry season. This shark is often found in markets, but is not highly regarded as a food fish. The International Union for Conservation of Nature (IUCN) has assessed this species as Critically Endangered
, as it has a limited distribution and is highly susceptible to overfishing
due to its low reproductive rate. The daggernose shark has declined over 90% over the past decade off Brazil, and similar declines have likely also occurred elsewhere in its range as fishing pressure in the region continues to grow more intense. The IUCN has urgently recommended the implementation of conservation schemes and the expansion of fishery monitoring for this species.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of requiem shark
Requiem shark
Requiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas such as the tiger shark, the blue shark, the bull shark, and the milk shark.The name may be related to the French word for shark, "requin", itself of...
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Carcharhinidae, and the only extant member of its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. It occurs in shallow tropical waters off northeastern South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
from Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
to northern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, favoring muddy habitats such as mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
s, estuaries, and river mouths, though it is intolerant of fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
. A relatively small shark typically reaching 1.5 m (4.9 ft) in length, the daggernose shark is unmistakable for its elongated, flattened, and pointed snout, tiny eyes, and large paddle-shaped pectoral fins.
Daggernose sharks are predators of small schooling fishes. Reproduction is viviparous, with females give birth to 2–8 pups every other year during the rainy season; this species is capable of shifting the timing of its reproductive cycle by several months in response to the environment. Harmless to humans, the daggernose shark is caught for food and as bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in artisanal
Artisan fishing
Artisan fishing is a term used to describe small scale low-technology commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and traditional...
and commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
. Limited in range and slow-reproducing, it has been assessed as Critically Endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
by International Union for Conservation of Nature in light of a steep population decline in recent years.
Taxonomy and phylogeny
The first scientific description of the daggernose shark, as Carcharias oxyrhynchus, was published by German biologists Johannes Peter MüllerJohannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
and Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...
in their 1839 Systematische Beschreibung der Plagiostomen. They chose the specific epithet oxyrhynchus, from the Greek oxys ("sharp" or "pointed") and rhynchos ("nose"). In 1862, American ichthyologist Theodore Gill
Theodore Gill
Theodore Nicholas Gill was an American ichthyologist, mammalogist, malacologist and librarian.Born and educated in New York City under private tutors, Gill early showed interest in natural history. He was associated with J...
coined the genus Isogomphodon for this species, from the Greek isos ("equal"), gomphos ("nail" or "peg"), and odous ("tooth"). However, Isogomphodon was subsequently relegated to being a synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
of Carcharhinus
Carcharhinus
Carcharhinus is the type genus of the requiem shark family, Carcharhinidae.- Species :* Carcharhinus acarenatus * Carcharhinus acronotus...
, until it was resurrected by shark authority Stewart Springer
Stewart Springer
Stewart Springer, was a world renowned expert on shark behavior, classification , and distribution of shark populations. There are more than 35 species of sharks, skates, rays, and other animals either classified originally by him or named after him.-Education:Springer was a field naturalist,...
in 1950. Regardless of its taxonomic validity, Isogomphodon, along with the genera Nasolamia and Prionace, is closely related to Carcharhinus. An extinct relative, I. acuarius, dates back to the Middle Eocene (45 Ma).
Distribution and habitat
The daggernose shark is found along the northeastern coast of South AmericaSouth America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, off Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
, Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...
, Suriname
Suriname
Suriname , officially the Republic of Suriname , is a country in northern South America. It borders French Guiana to the east, Guyana to the west, Brazil to the south, and on the north by the Atlantic Ocean. Suriname was a former colony of the British and of the Dutch, and was previously known as...
, French Guyana, and northern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. It reportedly occurs as far south as Valença
Valença, Bahia
Valença is a Brazilian municipality in the state of Bahia and has an estimated population of 82.000. It is visited by tourists because it is the main access to the island of Tinharé, famous for the town of Morro de São Paulo.- The town :...
in the central Brazilian state of Bahia
Bahia
Bahia is one of the 26 states of Brazil, and is located in the northeastern part of the country on the Atlantic coast. It is the fourth most populous Brazilian state after São Paulo, Minas Gerais and Rio de Janeiro, and the fifth-largest in size...
, though fishery
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
surveys have not detected this species in the area and it is apparently unknown to local fishermen.
An inhabitant of coastal waters at a depth of 4–40 m (13.1–131.2 ft), the daggernose shark prefers highly turbid waters and decreases in number with increasing water clarity. Females tend to be found at greater depths than males. Its range encompasses a wide continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
with a humid tropical climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
, extensive mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
s, and draining by numerous rivers including the Amazon
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
. Water salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
in this area ranges from 20 to 34 ppt, while the tidal amplitude
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
can measure up to 7 m (23 ft). Daggernose sharks are most common over shallow muddy banks and in estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
and river mouths. It seems to be intolerant of low salinity, moving inshore during the dry season
Dry season
The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
(June to November) and offshore during the rainy season (December to May). This species is not known to make long-distance movements, though some local seasonal movements are possible.
Description
As its common nameCommon name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
suggests, the daggernose shark has a very long, flattened snout with a pointed tip and an acutely triangular profile from above. The eyes are circular and minute in size, with nictitating membrane
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s (a protective third eyelid
Eyelid
An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...
). The nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s are small, without prominent nasal skin flaps. There are short but deep furrows at the corners of the mouth on both jaws. The tooth rows number 49–60 and 49–56 in the upper and lower jaws respectively. Each tooth has a single narrow, upright cusp; the upper teeth are slightly broader and flatter than the lower teeth, with serrated rather than smooth edges.
The body is robustly built, with large, broad, paddle-like pectoral fins that originate under the fifth gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
. The first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
originates over the posterior half of the pectoral fin bases. The second dorsal fin is about half as tall as the first and located over or slightly ahead of the anal fin. The anal fin is smaller than the second dorsal fin and has a deep notch in the rear margin. The caudal fin has a well-developed lower lobe and is preceded by a crescent-shaped notch on the upper side of the caudal peduncle. The coloration is a plain gray above, sometimes with a brownish or yellowish cast, and lighter below. Males attain a length of 1.4 m (4.6 ft) and females 1.6 m (5.2 ft). There are unsubstantiated records of individuals 2–2.4 m (6.6–7.9 ft) long. The maximum known weight is 13 kg (28.7 lb).
Biology and ecology
The dominant shark species within the daggernose shark's range are the smalltail sharkSmalltail shark
The smalltail shark is a species of requiem shark, family Carcharhinidae, found in the western Atlantic Ocean from the northern Gulf of Mexico to southern Brazil. It inhabits shallow waters close to shore, particularly over muddy bottoms around estuaries. It tends to swim low in the water column...
(Carcharhinus porosus) and the bonnethead
Bonnethead
The bonnethead shark or shovelhead, Sphyrna tiburo, is a member of the hammerhead shark genus Sphyrna. The Greek word sphyrna translates as hammer, referring to the shape of this shark's head - tiburo is the Taino word for shark....
(Sphyrna tiburo). Its elongated snout and tiny eyes are likely consequences of living in murky sediment-laden waters, reflecting an adaptive
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
emphasis on electroreception
Electroreception
Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...
and other rostral
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
senses rather than vision. The snout bears a superficial similarity to the goblin shark
Goblin shark
The goblin shark, Mitsukurina owstoni, is a deep-sea shark, the sole living species in the family Mitsukurinidae. The most distinctive characteristic of the goblin shark is the unusual shape of its head. It has a long, trowel-shaped, beak-like rostrum or snout, much longer than other sharks' snouts...
(Mitsukurina owstoni), some Apristurus
Apristurus
Apristurus is a genus of catshark, the family Scyliorhinidae, commonly known as the ghost or demon catsharks.-Species:* Apristurus albisoma Nakaya & Séret, 1999* Apristurus ampliceps Sasahara, Sato & Nakaya, 2008...
catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
s, and the long-nosed chimaeras
Rhinochimaeridae
Rhinochimaeridae, commonly known as long-nosed chimaeras, is a family of cartilaginous fish. They are similar in form and habits to other chimaeras, but have an exceptionally long, conical or paddle-shaped, snout. The snout has numerous sensory nerve endings, and is used to find food such as small...
, all found in the deep sea
Deep sea
The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter...
. With long jaws and numerous small teeth, the daggernose shark is well-suited for capturing the small schooling fishes that comprise most of its diet. Known prey taken include herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
, anchovies
Anchovy
Anchovies are a family of small, common salt-water forage fish. There are 144 species in 17 genera, found in the Atlantic, Indian, and Pacific Oceans. Anchovies are usually classified as an oily fish.-Description:...
, catfish
Catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
, and croakers
Sciaenidae
Sciaenidae is a family of fish commonly called drums, croakers, or hardheads for the repetitive throbbing or drumming sounds they make...
.
The daggernose shark is viviparous; once the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s exhaust their supply of yolk, the depleted yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
is converted into a placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
l connection through which the mother delivers sustenance. Females give birth to litters of 2–8 pups every other year, following a year-long gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
. There is no correlation between female size and number of offspring. Mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
and parturition take place over a roughly six-month period from the beginning to the end of the rainy season. However, the daggernose shark is capable of shifting the timing of its reproductive cycle by at least four months, possibly in response to varying environmental conditions. Females move into shallow coastal nurseries to give birth; one important nursery exists off Brazilian state of Maranhão
Maranhão
Maranhão is a northeastern state of Brazil. To the north lies the Atlantic Ocean. Maranhão is neighbored by the states of Piauí, Tocantins and Pará. The people of Maranhão have a distinctive accent...
.
Newly born daggernose sharks measure 38–43 cm (15–16.9 in) in length. Males mature at 103 cm (40.6 in) long, corresponding to an age of 5–6 years, while females mature at 115 cm (45.3 in) long, corresponding to an age of 6–7 years. The lifespan
Longevity
The word "longevity" is sometimes used as a synonym for "life expectancy" in demography or known as "long life", especially when it concerns someone or something lasting longer than expected ....
of males has been measured at up to 7 years, and females 12 years; extrapolating from growth rates suggest that the largest known males and females may be 12 and 20 years old respectively.
Human interactions
The daggernose shark poses little danger to humans due to its small size and teeth. This shark is caught in small numbers by subsistence fishersArtisan fishing
Artisan fishing is a term used to describe small scale low-technology commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and traditional...
in Trinidad, Guyana, Suriname, and French Guyana. It also comprises about one-tenth of the catch of a northern Brazil floating gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
fishery targeting Serra Spanish mackerel
Serra Spanish mackerel
The ', Scomberomorus brasiliensis, is a species of fish in the family Scombridae. Specimens have been recorded at up to 125 cm in length, and weighing up to 6,710 g. It is found in the western Atlantic, along the Caribbean and Atlantic coasts of Central and South America from Belize to Rio Grande...
(Scomberomorus brasiliensis) and Acoupa weakfish
Acoupa weakfish
The acoupa weakfish, Cynoscion acoupa, is a croaker of the family Sciaenidae, found in the western Atlantic from Panama to Argentina, at depths down to 20 m. Its length is up to 1.1 m....
(Cynoscion acoupa), which operates in estuaries during the dry season. This shark is often found in markets, but is not highly regarded as a food fish. The International Union for Conservation of Nature (IUCN) has assessed this species as Critically Endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
, as it has a limited distribution and is highly susceptible to overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
due to its low reproductive rate. The daggernose shark has declined over 90% over the past decade off Brazil, and similar declines have likely also occurred elsewhere in its range as fishing pressure in the region continues to grow more intense. The IUCN has urgently recommended the implementation of conservation schemes and the expansion of fishery monitoring for this species.