Blacknose shark
Encyclopedia
The blacknose shark is a species of requiem shark
, family Carcharhinidae, common in the tropical and subtropical waters of the western Atlantic Ocean
. This species generally inhabits coastal seagrass
, sand, or rubble habitat
s, with adults preferring deeper water than juveniles. A small shark typically measuring 1.3 m (4.1 ft) long, the blacknose shark has a typical streamlined "requiem shark" shape with a long rounded snout, large eyes, and a small first dorsal fin
. Its common name
comes from a characteristic black blotch on the tip of its snout, though this may be indistinct in older individuals.
Blacknose sharks feed primarily on small bony fishes and cephalopod
s, and in turn fall prey to larger sharks. Like other members of their family, they exhibit a viviparous mode of reproduction in which the developing embryo
s are sustained by a placenta
l connection. The females give birth to 3–6 young in late spring or early summer either annually or biennually, after a gestation period
of 8–11 months. This species is not known to attack
humans, though it has been documented performing a threat display
towards divers. It is of moderate commercial
and recreational
importance. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
. In 2009, the U.S. National Oceanic and Atmospheric Administration
(NOAA) announced that populations of the blacknose shark off the United States
are being overfished
, and proposed new conservation measures.
The Cuba
n naturalist Felipe Poey
published the first description of the blacknose shark in 1860 as Squalus acronotus, in his Memorias sobre la historia natural de la Isla de Cuba. Later authors moved this species to the genus
Carcharhinus
. The type specimen was a 98 cm (3.2 ft) long male caught off Cuba.
Based on morphological
data, Jack Garrick suggested in 1982 that the blacknose shark has a sister relationship to a group containing the whitecheek shark
(C. dussumieri) and the blackspot shark
(C. sealei), while Leonard Compagno
proposed in 1988 that this shark belongs in a group with 5 other species including the silky shark
(C. falciformis) and the blacktip reef shark
(C. melanopterus). Molecular analyses have been similarly equivocal regarding the blacknose shark's phylogenetic relationships: Gavin Naylor's 1992 allozyme
analysis found this species to be the most basal
member of Carcharhinus, while Mine Dosay-Abkulut's 2008 ribosomal DNA
analysis indicated affinity between it and the blacktip shark
(C. limbatus) or the smalltail shark
(C. porosus). The whitenose shark
(Nasolamia velox), found along the tropical western coast of the Americas
, may be descended from blacknose sharks that experienced the teratogenic
effects of incipient cyclopia
.
and as far south as southern Brazil
, including the Bahamas, the Gulf of Mexico
, and the Caribbean Sea
. They frequent coastal waters over beds of seagrass, sandy flats, and shell or coral
rubble. This species is spatially segregated by size and sex. Generally only young sharks are encountered in shallow water, as the adults prefer depths greater than 9 m (30 ft) and is most common at 18–64 m (59.1–210 ft). Blacknose sharks in the South Atlantic Bight (off the Atlantic coast of the southern United States) migrate
northward in the summer and southward (or possibly offshore) in the winter; a similar migration occurs for sharks in the Gulf of Mexico.
The blacknose shark has a slender, streamlined body with a long, rounded snout and large eyes. There is a well-developed flap of skin in front of each nostril
, defining the inflow and outflow openings. There are 12–13 and 11–12 tooth rows on either side of the upper and lower jaws respectively, with 1–2 teeth at the symphysis
(middle). The teeth are triangular and oblique, with serrated edges; the upper teeth are stouter than the lower teeth. The five pairs of gill slit
s are short, measuring less a third the length of the first dorsal fin base.
The first dorsal fin is small and somewhat falcate (sickle-shaped), with a pointed apex and a short free rear tip; its origin lies over the free rear tips of the pectoral fins. The second dorsal fin is relatively large, though still less than half the height of the first. There is no ridge between the dorsal fins. The pectoral fins are short and tapered. The body is covered with overlapping dermal denticles that bear 5–7 longitudinal ridges (3 in very young individuals) leading to 3–5 marginal teeth. The coloration is yellowish to greenish gray or brown above and white to yellow below. There is a distinctive dark blotch at the tip of the snout that is most obvious in young sharks. The tips of the second dorsal fin, upper caudal fin lobe, and sometimes the lower caudal fin lobe, are dark. Blacknose sharks are typically 1.3–1.4 m (4.1–4.6 ft) long and 10 kg (22 lb) in weight. The maximum length and weight on record is 2.0 m (6.6 ft) and 18.9 kg (42 lb) respectively.
, porgies
, anchovies, spiny boxfish, and porcupinefish
, as well as on octopus
and other cephalopods. When competing for bait, their speed allows them to snatch food from larger sharks such as the Caribbean reef shark
(C. perezi). This species may form large school
s that are sometimes associated with anchovies and mullet
. Blacknose sharks demonstrate a high degree of philopatry
: both juveniles and adults have been documented returning to the same local area year after year.
Blacknose sharks are preyed upon by larger sharks. Captive blacknose sharks have been observed to perform an apparent threat display
towards encroaching divers or newly introduced members of their species. The display consists of the shark hunching its back, lowering its pectoral fins, gaping its jaws, and swimming with an exaggerated side-to-side motion. Known parasites of this species include the copepod
s Nesippus orientalis, Perissopus dentatus, Pandarus sinuatus, Kroyeria sphyrnae, Nemesis atlantica, and Eudactylina spinifera, as well as tapeworms in the genera Paraorygmatobothrium and Platybothrium.
develops into a placental connection through which the mother provides nourishment. Off the United States, males are thought to reproduce every year while females reproduce every other year. However, off northeastern Brazil, the female reproductive cycle is short enough to occur annually. Vitellogenesis
(the formation of yolk within the ovary
) occurs in the late summer, and is immediately followed by mating
and fertilization in the fall, with the young being born the following spring to summer. The seasonality of these events means that the reproductive cycle is offset by six months between populations in the Northern and Southern Hemispheres. The gestation period
has been variously estimated at 8 months off northeastern Brazil and 9 or 10–11 months off the southeastern United States.
Females typically give birth to litters of 1–6 pups in shallow nursery areas such as coastal bays or mangrove swamps; one known nursery area is Bulls Bay off South Carolina
. There is no relationship between female size and the number of young. The newborns measure 38–50 cm (15–20 in) long. Female blacknose sharks grow more slowly, attain a larger ultimate size, and have a longer lifespan than males. In addition, Gulf of Mexico sharks are slower-growing and longer-lived than those from the South Atlantic Bight. In the South Atlantic Bight, both sexes mature at a fork length (from snout tip to caudal fin fork) of around 90 cm (3.0 ft), corresponding to ages of 4.3 years for males and 4.5 years for females. In the Gulf of Mexico, both sexes mature at a fork length of around 85 cm (2.8 ft), corresponding to ages of 5.4 years for males and 6.6 years for females. The maximum lifespan has been calculated as 19 years in South Atlantic Bight and 16.5 years in the Gulf of Mexico.
The blacknose shark has never been implicated in an attack on humans. However, caution should be exercised if it begins to perform a threat display. This species is regarded as a game fish
and offers a respectable fight on light tackle
(a more delicate fishing line). It is also of regional commercial importance, being taken intentionally and otherwise
via gillnet
s and surface longlines across its range, most significantly off southwestern Florida
, Venezuela
, and Brazil
; the meat is sold dried and salted. Large numbers of blacknose sharks are also caught incidentally
by shrimp
trawlers, which may pose a greater threat to its population as many of the sharks taken are immature.
Off the United States, the fishing of the blacknose shark is regulated by the U.S. National Marine Fisheries Service
1993 Fisheries Management Plan (FMP) for Atlantic and Gulf of Mexico sharks. For the purposes of commercial quotas and bag limits, the blacknose shark is classified within the "Small Coastal Shark" (SCS) complex. From 1999 to 2005, an average of 27,484 blacknose sharks (62 metric tons) were caught each year off the United States. Recent stock assessments conducted by the U.S. National Oceanic and Atmospheric Administration
(NOAA) have determined that populations of this species have become overfished in both the Atlantic and the Gulf of Mexico. In 2009, the NOAA proposed instituting a separate quota for blacknose sharks of 6,065 sharks per year, and a ban on using gillnets to catch sharks in the Atlantic. By contrast, blacknose shark stocks off northern Brazil appear to be stable, while no fishery data is available from the Caribbean
. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
globally.
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 Carcharhinidae, common in the tropical and subtropical waters of the western Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. This species generally inhabits coastal seagrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
, sand, or rubble habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s, with adults preferring deeper water than juveniles. A small shark typically measuring 1.3 m (4.1 ft) long, the blacknose shark has a typical streamlined "requiem shark" shape with a long rounded snout, large eyes, and a small 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...
. Its common name
Common 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...
comes from a characteristic black blotch on the tip of its snout, though this may be indistinct in older individuals.
Blacknose sharks feed primarily on small bony fishes and cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, and in turn fall prey to larger sharks. Like other members of their family, they exhibit a viviparous mode of reproduction in which 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 are sustained by 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. The females give birth to 3–6 young in late spring or early summer either annually or biennually, after a 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:...
of 8–11 months. This species is not known to attack
Shark attack
A shark attack is an attack on a human by a shark. Every year around 60 shark attacks are reported worldwide, although death is quite unusual. Despite the relative rarity of shark attacks, the fear of sharks is a common phenomenon, having been fueled by the occasional instances of serial attacks,...
humans, though it has been documented performing a threat display
Shark threat display
Shark threat display, a type of agonistic display, is a behaviour observed in some sharks when they feel threatened or protective. It consists of a contorting of the body into a series of "ritualized" postures coupled with an exaggerated swimming style...
towards divers. It is of moderate commercial
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...
and recreational
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
importance. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
. In 2009, the U.S. National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
(NOAA) announced that populations of the blacknose shark off the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
are being overfished
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....
, and proposed new conservation measures.
Taxonomy and phylogeny
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
n naturalist Felipe Poey
Felipe Poey
-Biography:Poey was born in Havana, the son of French and Spanish parents. He spent several years of his life in Pau then studied law in Madrid. He became a lawyer in Spain but was forced to leave due to his liberal ideas, returning to Cuba in 1823. He began to concentrate on the study of the...
published the first description of the blacknose shark in 1860 as Squalus acronotus, in his Memorias sobre la historia natural de la Isla de Cuba. Later authors moved this species to the 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...
Carcharhinus
Carcharhinus
Carcharhinus is the type genus of the requiem shark family, Carcharhinidae.- Species :* Carcharhinus acarenatus * Carcharhinus acronotus...
. The type specimen was a 98 cm (3.2 ft) long male caught off Cuba.
Based on morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
data, Jack Garrick suggested in 1982 that the blacknose shark has a sister relationship to a group containing the whitecheek shark
Whitecheek shark
The whitecheek shark, Carcharhinus dussumieri, is a requiem shark of the family Carcharhinidae, found in the Indo-West Pacific Ocean between latitudes 34° N and 25° S. Its length is up to about 1.2 m....
(C. dussumieri) and the blackspot shark
Blackspot shark
The blackspot shark, Carcharhinus sealei, is a requiem shark of the family Carcharhinidae, found in the Indo-West Pacific oceans between latitudes 24° N and 30° S, from the surface to 40 m. Its length is up to about 1.5 m....
(C. sealei), while Leonard Compagno
Leonard Compagno
Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...
proposed in 1988 that this shark belongs in a group with 5 other species including the silky shark
Silky shark
The silky shark is a species of requiem shark, family Carcharhinidae, named for the smooth texture of its skin. It is one of the most abundant sharks in the pelagic zone, and can be found around the world in tropical waters. Highly mobile and migratory, this shark is most often found over the edge...
(C. falciformis) and the blacktip reef shark
Blacktip reef shark
The blacktip reef shark is a species of requiem shark, family Carcharhinidae, easily identified by the prominent black tips on its fins...
(C. melanopterus). Molecular analyses have been similarly equivocal regarding the blacknose shark's phylogenetic relationships: Gavin Naylor's 1992 allozyme
Allozyme
Variant forms of an enzyme that are coded by different alleles at the same locus are called allozymes. These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci....
analysis found this species to be the most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
member of Carcharhinus, while Mine Dosay-Abkulut's 2008 ribosomal DNA
Ribosomal DNA
Ribosomal DNA codes for ribosomal RNA. The ribosome is an intracellular macromolecule that produces proteins or polypeptide chains. The ribosome itself consists of a composite of proteins and RNA. As shown in the figure, rDNA consists of a tandem repeat of a unit segment, an operon, composed of...
analysis indicated affinity between it and the blacktip shark
Blacktip shark
The blacktip shark is a species of requiem shark, family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean...
(C. limbatus) or the smalltail shark
Smalltail 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...
(C. porosus). The whitenose shark
Whitenose shark
The whitenose shark is a shark of the family Carcharhinidae. The only member of the genus Nasolamia, it is found in the tropical waters of the eastern Pacific Ocean between latitudes 31° N and 18° S, from depths of 15 to 200 m...
(Nasolamia velox), found along the tropical western coast of the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, may be descended from blacknose sharks that experienced the teratogenic
Teratology
Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human birth defects, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants.- Etymology :The...
effects of incipient cyclopia
Cyclopia
Cyclopia is a rare form of holoprosencephaly and is a congenital disorder characterized by the failure of the embryonic prosencephalon to properly divide the orbits of the eye into two cavities...
.
Distribution and habitat
The blacknose shark inhabits the continental and insular shelves off the eastern coast of the Americas, as far north as North CarolinaNorth Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
and as far south as southern 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...
, including the Bahamas, the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
, and the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
. They frequent coastal waters over beds of seagrass, sandy flats, and shell or coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
rubble. This species is spatially segregated by size and sex. Generally only young sharks are encountered in shallow water, as the adults prefer depths greater than 9 m (30 ft) and is most common at 18–64 m (59.1–210 ft). Blacknose sharks in the South Atlantic Bight (off the Atlantic coast of the southern United States) migrate
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
northward in the summer and southward (or possibly offshore) in the winter; a similar migration occurs for sharks in the Gulf of Mexico.
Description
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...
, defining the inflow and outflow openings. There are 12–13 and 11–12 tooth rows on either side of the upper and lower jaws respectively, with 1–2 teeth at the symphysis
Symphysis
A symphysis is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint.1.A symphysis is an amphiarthrosis, a slightly movable joint.2.A growing together of parts or structures...
(middle). The teeth are triangular and oblique, with serrated edges; the upper teeth are stouter than the lower teeth. The five pairs of 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...
s are short, measuring less a third the length of the first dorsal fin base.
The first dorsal fin is small and somewhat falcate (sickle-shaped), with a pointed apex and a short free rear tip; its origin lies over the free rear tips of the pectoral fins. The second dorsal fin is relatively large, though still less than half the height of the first. There is no ridge between the dorsal fins. The pectoral fins are short and tapered. The body is covered with overlapping dermal denticles that bear 5–7 longitudinal ridges (3 in very young individuals) leading to 3–5 marginal teeth. The coloration is yellowish to greenish gray or brown above and white to yellow below. There is a distinctive dark blotch at the tip of the snout that is most obvious in young sharks. The tips of the second dorsal fin, upper caudal fin lobe, and sometimes the lower caudal fin lobe, are dark. Blacknose sharks are typically 1.3–1.4 m (4.1–4.6 ft) long and 10 kg (22 lb) in weight. The maximum length and weight on record is 2.0 m (6.6 ft) and 18.9 kg (42 lb) respectively.
Biology and ecology
A small, fast-swimming predator, the blacknose shark feeds primarily on small bony fishes, including pinfish, croakersSciaenidae
Sciaenidae is a family of fish commonly called drums, croakers, or hardheads for the repetitive throbbing or drumming sounds they make...
, porgies
Sparidae
The Sparidae is a family of fish, included in the order Perciformes. The fish of the family are commonly called sea breams and porgies . The sheepshead, scup, and red sea bream are species in this family. They are found in shallow temperate and tropical waters and are bottom-dwelling carnivores....
, anchovies, spiny boxfish, and porcupinefish
Porcupinefish
Porcupinefish are fish of the family Diodontidae, , also commonly called blowfish ....
, as well as on octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
and other cephalopods. When competing for bait, their speed allows them to snatch food from larger sharks such as the Caribbean reef shark
Caribbean reef shark
The Caribbean reef shark is a species of requiem shark, family Carcharhinidae. It is found in the tropical waters of the western Atlantic Ocean from Florida to Brazil, and is the most commonly encountered reef shark in the Caribbean Sea...
(C. perezi). This species may form large school
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
s that are sometimes associated with anchovies and mullet
Mullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
. Blacknose sharks demonstrate a high degree of philopatry
Philopatry
Broadly, philopatry is the behaviour of remaining in, or returning to, an individual's birthplace. More specifically, in ecology philopatry is the behaviour of elder offspring sharing the parental burden in the upbringing of their siblings, a classic example of kin selection...
: both juveniles and adults have been documented returning to the same local area year after year.
Blacknose sharks are preyed upon by larger sharks. Captive blacknose sharks have been observed to perform an apparent threat display
Shark threat display
Shark threat display, a type of agonistic display, is a behaviour observed in some sharks when they feel threatened or protective. It consists of a contorting of the body into a series of "ritualized" postures coupled with an exaggerated swimming style...
towards encroaching divers or newly introduced members of their species. The display consists of the shark hunching its back, lowering its pectoral fins, gaping its jaws, and swimming with an exaggerated side-to-side motion. Known parasites of this species include the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s Nesippus orientalis, Perissopus dentatus, Pandarus sinuatus, Kroyeria sphyrnae, Nemesis atlantica, and Eudactylina spinifera, as well as tapeworms in the genera Paraorygmatobothrium and Platybothrium.
Life history
As in other requiem sharks, the blacknose shark is viviparous: after the developing embryos exhaust their supply of yolk, the empty yolk sacYolk 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...
develops into a placental connection through which the mother provides nourishment. Off the United States, males are thought to reproduce every year while females reproduce every other year. However, off northeastern Brazil, the female reproductive cycle is short enough to occur annually. Vitellogenesis
Vitellogenesis
Vitellogenesis is the process of yolk formation via nutrients being deposited in the oocyte, or female germ cell involved in reproduction. It starts when the fat body stimulates the release of juvenile hormones and produces vitellogenin protein. It occurs in all animal groups lower than the mammals...
(the formation of yolk within the ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
) occurs in the late summer, and is immediately followed by 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 fertilization in the fall, with the young being born the following spring to summer. The seasonality of these events means that the reproductive cycle is offset by six months between populations in the Northern and Southern Hemispheres. The 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:...
has been variously estimated at 8 months off northeastern Brazil and 9 or 10–11 months off the southeastern United States.
Females typically give birth to litters of 1–6 pups in shallow nursery areas such as coastal bays or mangrove swamps; one known nursery area is Bulls Bay off South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
. There is no relationship between female size and the number of young. The newborns measure 38–50 cm (15–20 in) long. Female blacknose sharks grow more slowly, attain a larger ultimate size, and have a longer lifespan than males. In addition, Gulf of Mexico sharks are slower-growing and longer-lived than those from the South Atlantic Bight. In the South Atlantic Bight, both sexes mature at a fork length (from snout tip to caudal fin fork) of around 90 cm (3.0 ft), corresponding to ages of 4.3 years for males and 4.5 years for females. In the Gulf of Mexico, both sexes mature at a fork length of around 85 cm (2.8 ft), corresponding to ages of 5.4 years for males and 6.6 years for females. The maximum lifespan has been calculated as 19 years in South Atlantic Bight and 16.5 years in the Gulf of Mexico.
Human interactions
Game fish
Game fish are fish pursued for sport by recreational anglers. They can be freshwater or marine fish. Game fish can be eaten after being caught, though increasingly anglers practise catch and release to improve fish populations. Some game fish are also targeted commercially, particularly...
and offers a respectable fight on light tackle
Fishing tackle
Fishing tackle, is a general term that refers to the equipment used by fishermen when fishing. Almost any equipment or gear used for fishing can be called fishing tackle. Some examples are hooks, lines, sinkers, floats, rods, reels, baits, lures, spears, nets, gaffs, traps, waders and tackle...
(a more delicate fishing line). It is also of regional commercial importance, being taken intentionally and otherwise
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...
via 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...
s and surface longlines across its range, most significantly off southwestern Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
, and 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...
; the meat is sold dried and salted. Large numbers of blacknose sharks are also caught incidentally
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...
by shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
trawlers, which may pose a greater threat to its population as many of the sharks taken are immature.
Off the United States, the fishing of the blacknose shark is regulated by the U.S. National Marine Fisheries Service
National Marine Fisheries Service
The National Marine Fisheries Service is a United States federal agency. A division of the National Oceanic and Atmospheric Administration and the Department of Commerce, NMFS is responsible for the stewardship and management of the nation's living marine resources and their habitat within the...
1993 Fisheries Management Plan (FMP) for Atlantic and Gulf of Mexico sharks. For the purposes of commercial quotas and bag limits, the blacknose shark is classified within the "Small Coastal Shark" (SCS) complex. From 1999 to 2005, an average of 27,484 blacknose sharks (62 metric tons) were caught each year off the United States. Recent stock assessments conducted by the U.S. National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
(NOAA) have determined that populations of this species have become overfished in both the Atlantic and the Gulf of Mexico. In 2009, the NOAA proposed instituting a separate quota for blacknose sharks of 6,065 sharks per year, and a ban on using gillnets to catch sharks in the Atlantic. By contrast, blacknose shark stocks off northern Brazil appear to be stable, while no fishery data is available from the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
globally.