Spinner Sharks

[steve75]

Does anybody ever heard of Spinner Sharks?A friend of me said he saw them on his recent vacation,I never heard the name before.I heard of Spinner Dolphins.Is it a mix up?

[knotical]

Lots of hits on Google for “spinner shark”. Here are just a couple:
www.espn.go.com/outdoors/general/s/f_enc_SpinnerShark.html
www.flmnh.ufl.edu/fish/Gallery/Descript/spinnershark/spinnershark.html

[jcjetty]

I was satellite surfing one day and ran acros a show on offshore fishing, being land locked at the time I was of course feeding my "big blue" addiction. Any how I did see a couple guys fishing for spinner sharks off the atlantic coast of Florida, Miami if I remember right,. The thing that sticks in my memory is how compact and muscular they are, if a little short, which makes me thing they are pretty agressive hunters. I also remember that these guys where catching these critters fairly close to shore, much to the dismay of the bathers,.

last year I was in Ft. Lauderdale and did a lot of diving but never saw one. I also asked one of the locals about "spinner sharks" and he said he had no idea. So what we may have is a common name that only fisherman use.

Looking through Paul Humann's id book I have to wonder if they might be a sandbar shark...Ask your friend to take a look and let me know if it may be one and the same.

Cheers.

[LSDeep]

SPINNER SHARK
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species: brevipinna

Spinner Shark

Taxonomy

Müller & Henle first described the spinner shark as Carcharias brevipinna in 1839. Shortly thereafter, this shark went through a series of name changes including Squalus brevipinna, Aprionodon brevipinna, and finally the currently valid name Carcharhinus brevipinna. The genus name Carcharhinus is derived from the Greek "karcharos" = sharpen and "rhinos" = nose. Synonyms referring to this shark in past scientific literature include Isogomphodon maculipinnis Poey 1865, Carcharhinus maculipinnis Poey 1865, Uranga nasuta Whitley 1943, Longmania calamaria Whitely 1944, Carcharinus johnsoni Smith 1951, Aprionodon caparti Poll 1951, and Carcharhinus johnsoni Smith 1951. It is also often confused with blacktip shark, Carcharhinus limbatus, due to similar characteristics.

Common Names

English language common names for Carcharhinus brevipinna include spinner shark, blacktipped shark, great blacktip shark, large blacktip shark, long-nose grey shark, and shark. Other names from across the world include cação-agulha-preta (Portuguese), chotimushi (Marathi), galha-preta (Portuguese), hanazame (Japanese), jaqueton (Spanish), jarjur (Arabic), jarjur naudth (Arabic), karcharynos kontofteros (Greek), köpek baligi (Turkish), machote (Portuguese), marracho barbatana negra (Portuguese), mushi (Marathi), pating (Tagalog), requin nene pointe (French), requin tisserand (French), serra-garoupa (Portuguese), shivra (Kannada), spinnerhaai (Afrikans), squalo tissitore (Italian), sucuri-de-ponta-petra (Portuguese), tiburon aleta negra (Spanish), tolhaai (Dutch), and tubarão-tecelão (Portuguese).

Geographical Distribution

The spinner shark is found in the western Atlantic from North Carolina (U.S.) to the northern Gulf of Mexico and the Bahamas. This shark has also been reported in waters around Cuba. It also resides from southern Brazil to northern Argentina. In the eastern Atlantic Ocean, it is found from Spain to Namibia, including the southern Mediterranean Sea. In the Indo-West Pacific, the spinner shark is found in the Red Sea, south to South Africa, eastward to Indonesia, northward to Japan, and then south to Australian waters.

Distribution records are probably incomplete due to confusion over species identification with the blacktip shark (C. limbatus).



Habitat

Distributed from inshore to offshore waters over continental and insular shelves, the spinner shark lives in subtropical regions primarily between 40°N and 40°S. Depth of habitat ranges from 0-328 feet (0-100 m). The spinner shark forms schools and is considered a highly migratory species off the Florida and Louisiana coasts and in the Gulf of Mexico, moving inshore during spring and summer months to reproduce and feed.

Although juvenile spinner sharks move into lower portions of bays with the tides, they avoid areas of low salinity.

The spinner shark is an active, fast swimming shark that is often seen leaping out of the water, spinning (from where it gets its common name), in pursuit of prey.

Biology

· Distinctive Features
This shark has a slender build with a long, pointed snout. The lower jaw has a distinct notch along the trailing edge. The eyes are round and small in size. The first dorsal fin is small and semifalcate, originating above and behind the pectoral fin. This dorsal fin has a short rear tip followed by a moderately large second dorsal with a short rear tip. An inter-dorsal ridge is absent. The pectoral fins are narrow and falcate with narrow pointed or rounded tips. The caudal fin is slender with a narrowly rounded tip.


It is often confused with the blacktip shark (C. limbatus), however it is possible to distinguish these two species. The first dorsal fin of the blacktip shark at midpoint of pectoral fin inner margin in contrast to the spinner shark where the first dorsal originates or behind the rear tips of the pectoral fins. While this difference is useful in the identification of adults, it cannot be used to distinguish juveniles. The shape of the first dorsal fin also differs between the two species. In the spinner shark, the posterior edge of the fin is approximately perpendicular to the horizontal axis of the body and the tip is more rounded. The blacktip shark's first dorsal fin has a slightly falcate trailing edge. Another difference is the anal fin of the spinner is tipped in black while the blacktip shark lacks this marking. However, this black marking can fade on dead sharks.


·<br>

A side by side comparision of a spinner shark and a blacktip shark, notice the black tip on the anal fin of the spinner shark which is absent on the blacktip shark.
© Pete Cooper/FLMNH Ichthyology



World distribution map for the spinner shark



Spinner shark
© George Burgess

[LSDeep]

Coloration
The spinner shark is gray to bronze in color, fading to a white underside with a faint white band on the sides. The second dorsal, anal, and pectoral fins as well as the lower lobe of the caudal fin have black or dark gray tips in large juveniles and adults. The pelvic, first dorsal, and dorsal caudal lobe may also have black tips, but not always. The fins are unmarked in young individuals.


· Dentition
The teeth in the upper jaw of the spinner shark have narrow triangular cusps on broad bases. This differs from the blacktip shark, which has larger and broader teeth. The first few teeth are symmetrical and erect with subsequent teeth becoming slightly oblique. The outer three teeth are very low with finely serrated edges with smooth-edged tips.

The lower jaw teeth have more slender cusps on broad bases than the upper jaw. The tips of the teeth are not recurved forward as in the blacktip shark. The teeth are slightly oblique along the entire length of the jaw.

There are two small teeth located at the symphysis in the upper jaw and one small tooth in the lower jaw. The rows of teeth in each jaw vary in number from 14-18, but usually number 16/15.


· Denticles
The dermal denticles of the spinner shark are very closely arranged, even overlapping, concealing the skin. The blades are slightly raised and are broader than long. The ridges number usually 7 (rarely 5), with 7 very short or entirely even teeth.


·Size, Age, and Growth
Spinner sharks reach a maximum total length of 9.8 feet (3 m) and a maximum weight of 198 pounds (89.7 kg). However, the average size of these sharks is about 6.4 feet (1.95 m) and 123 pounds (56 kg). Female spinner sharks mature at 5.6-6.6 feet (1.7-2.0 m) TL and males mature at 5.2-6.7 feet (1.6-2.0 m) TL. Upon reaching maturity, the spinner shark grows approximately 2 inches/yr (5 cm/yr), reaching maximum size at 10-20 years of age. This species is generally smallest in the northwestern Atlantic and largest in the Indian Ocean and Indo-West Pacific.

According to one study, the spinner shark grows approximately 8 inches (20 cm) during the first 6 months of life in waters off the Florida Atlantic coast.


· Food Habits
The spinner shark feeds primarily on pelagic fishes including ten-pounders, sardines, herrings, anchovies, sea catfish, lizardfish, mullet, bluefish, tunas, bonito, croakers, jacks, mojarras, grunts, tongue-soles, stingrays, cuttlefish, squid, and octopi. It has an unusual method of feeding, swimming rapidly through schools, spinning along the axis of its body. The shark snaps in all directions at the quickly scattering fish, followed by leaping out of the water. This feeding behavior has also been reported for the blacktip shark (C. limbatus), although to a lesser degree. During feeding and scavenging events, spinner sharks sometimes form aggregations. These sharks have been also reported to scavenge discarded fish from fishing vessels.


· Reproduction
Spinner sharks are "viviparous", or livebearing, with embryos nourished by a yolksac-placenta. The gestation period lasts 12-15 months with birth occurring at inshore locations during the summer months for stocks located off North America. Stocks located in the Mediterranean move inshore to give birth during summer off the North African coast. Litter size is from 3-15 pups, each measuring between 24-30 inches(60-75 cm) in length. The pups immediately move into shallow estuarine waters for protection from predators and readily available food sources.


Predators
Larger sharks are potential predators of the spinner shark, especially on juvenile and subadult individuals.


Parasites
Kroyeria deetsi n.sp. is a parasitic copepod that has been reported to infect the gills of spinner sharks captured in the Indian Ocean. Other parasitic copepods reported associated with spinner sharks include Alebion carchariae (body surface), Nesippus orientalis (gill arches and in the mouth), Perissopus dentatus (external nares and trailing edges of fins), Nemesis pilosus (gills) and Nemesis atlantica (gills).


Importance to Humans

Spinner sharks are taken primarily on longlines in the commercial shark fishery and as by-catch in the pelagic longline fishery. It is taken in lesser quantities by anglers trolling and stilt fishing. When it is hooked, this shark is known to make vertical spinning leaps out of the water. The flesh is marketed fresh and dried-salted for human consumption while the skins are valuable for leather and fins used in shark-fin soup.

Danger to Humans

Although the spinner shark is not considered dangerous to humans, it may pose a threat if attracted to divers during spearfishing activities. According to the International Shark Attack File, the spinner shark has been responsible for 13 unprovoked attacks on humans resulting in no fatalities. However, its small, narrow teeth are much more suited to feeding on whole small fishes, not attacking large prey such as marine mammals and humans.

Conservation

Due to the fact that this shark is frequently captured in the commercial and recreational fisheries, it is highly vulnerable to fishing pressure. In addition, the spinner shark utilizes inshore waters as nursery areas making it also susceptible to habitat alteration from development of shoreline areas.

The spinner shark is currently listed by the World Conservation Union (IUCN) as "Near Threatened" throughout its range and "Vulnerable" in the northwest Atlantic Ocean. 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


hope that helps ;D and yes they are often close to shore. while working in palm beach, florida i saw them quite often within 100ft of the shore.