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Biological Profiles




BLACKNOSE SHARK
Order - Carcharhiniformes
Family - Carcharhinidae
Genus - Carcharhinus
Species - acronotus
Blacknose Shark

Taxonomy

This shark was first described and named Squalus acronotus by Cuban naturalist Felipe Poey in 1860. This name was changed to the currently valid name Carcharhinus acronotus by Poey during that same year. The genus name Carcharhinus is derived from the Greek "karcharos" = sharpen and "rhinos" = nose. Synonyms include Carcharias (Prionodon) remotus (Dumeril, 1865) and perhaps Prionodon curcuri (Castelnau, 1855). Representing 25 living species, the Carcharhinidae is one of the largest families of sharks. Sharks in this family are also commonly referred to as "requiem sharks".


Common Names

The common name for Carcharhinus acronotus throughout English-speaking countries is the blacknose shark. Other names include cação (Portuguese), cazon amarillo (Spanish), hanagurozame (Japanese), lombo-preto (Spanish), requin nez noir (French), sarda (Spanish), tiburon amarillo (Spanish), and zwartsnuithaai (Dutch).


Geographical Distribution

The distribution of the blacknose shark is limited to the western Atlantic Ocean from North Carolina (USA) south to southern Brazil, including the Caribbean Sea, Bahamas, and Gulf of Mexico.


map
World distribution map for the blacknose shark


Habitat

This shark is found in coastal tropical and warm temperate waters of the western Atlantic Ocean. As an inshore species, the blacknose shark resides in waters of continental shelves over sandy and coral bottoms. There is segregation by size and sex in this species. Juveniles are typically found in shallow water while adults are located at greater depths (over 30 feet (9 m)). This shark is known to form large schools and sometimes associates with schools of mullet and anchovies.


Biology
Blacknose shark
© George Burgess
· Distinctive Features
Blacknose sharks are relatively small and slender with a somewhat long rounded snout and large eyes. This shark gets its common name from the characteristic black or dusky spot under the tip of the snout. The origin of the first dorsal fin is located over the free margins of the pectoral fins; the origin of the second dorsal fin is over or slightly anterior of anal fin origin. The margin of the anal fin is deeply notched. The interdorsal ridge (ridge between dorsal fins) is absent in this species and the caudal peduncle lacks a keel.


Juvenile blacknose shark showing the distinctive black spot under the tip of the snout
© George Burgess



· Coloration
The blacknose shark is gray to greenish gray with black or dusky tips on the second dorsal fin and dorsal caudal lobe. There is a black or dusky spot under the tip of the snout which is more distinct in younger individuals, hence the common name "blacknose shark". This spot makes this shark easy to distinguish from other gray shark species that occur in the same region.


Blacknose shark dentition, A. Third upper tooth, B. Eighth upper tooth, C. Third lower tooth, D. Eighth lower tooth, E. Left-hand upper and lower teeth
source Bigelow and Schroeder (1948) FNWA



·Dentition
The upper jaw of the blacknose shark has 12-13 rows of teeth on each side with 11-12 rows on the lower jaw. Teeth on the upper jaw are moderately narrow and triangular with oblique cusps along with coarser serrations along the bases than the tips. The lower jaw also has cusped serrated teeth with broad bases. There is one symphysial tooth in the upper jaw and one or two in the lower jaw.


Blacknose shark denticles, A. Apical view of dermal denticle, B. Dermal denticles
source Bigelow and Schroeder (1948) FNWA



·Denticles
Dermal denticles of the blacknose shark are closely spaced and overlapping. Each denticle has three longitudinal ridges and three posterior marginal teeth in embryos and young individuals while subadults and adults have denticles with 5 or 7 longitudinal ridges and 3-5 posterior marginal teeth.


Blacknose shark
courtesy Virginia Institute of Marine Science



·Size, Age, and Growth
The average length of a full-grown blacknose shark is approximately 4.1 feet (125 cm TL), reaching a maximum size of 4.6 feet (140cm TL). Depending on geographic location, maximum age is 10-16 years for females and 4.5-9 years for males. A recent study has reported a maximum age of 11.5 years for female blacknose sharks and 9.5 years for male blacknose sharks in the Gulf of Mexico. (Carlson et al. 2007) This shark commonly weighs about 22 pounds (10 kg) at maturity. A relatively fast growing species, males reach maturity at 3-3.5 feet (95-105 cm), while females reach maturity at lengths between 3.3-3.5 feet (100 and 105 cm). Both sexes mature at about 2 years of age.


Sheepshead porgy (Calamus penna) are prey for the blacknose shark
© David Snyder
· Food Habits
The blacknose shark is a quick swimmer, feeding on small fishes including pinfish, croakers, porgies, anchovies, spiny boxfishes, and porcupine fish. It is also known to feed on octopus.


Juvenile blacknose shark
© George Burgess



· Reproduction
Blacknose sharks mate in late May/ early June and have a 10-11 month gestation period. Currently blacknose sharks appear to exhibit two different reproductive cycles in the Northwestern Atlantic and Gulf of Mexico. Studies have shown that female blacknose shark in the Gulf of Mexico reproduce annually, with yolk development (vitellogenesis) occurs concurrently with the late stages of gestation. However, female blacknose sharks in the Atlantic appear to reproduce biennially (once every 2 years).

Litter size for the blacknose shark is 3-6, but the usual number is 4. At birth, the young measure 17-20" (43-51 cm) in length. Bulls Bay, South Carolina (U.S.) is one known nursery area for this species.


Dusky sharks often feed on blacknose sharks
© George Burgess



· Predators
Blacknose sharks may fall prey to larger sharks, including the dusky shark (Carcharhinus obscurus).


New-born blacknose sharks are caught by recreational fishers in the northern Gulf of Mexico
© Stacey Sandrey
Importance to Humans

Blacknose sharks are of minor commerical fishery importance, however it is fished as a gamefish, for the decent fight it gives when caught on light tackle. When it is harvested, this shark is often dried prior to being marketed for human consumption.


Danger to Humans

This shark poses little threat to humans and has never been reported in a shark attack case. However, when confronted by divers, the blacknose shark has been reported to give a threat display in the form of a hunched back with head raised and caudal lowered.

Blacknose shark up-close
© George Burgess




Conservation

The blacknose shark is currently not listed by the World Conservation Union (IUCN) as endangered or threatened at this time. The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.


Prepared by:
Cathleen Bester