Odontaspis ferox
Odontaspis ferox
The smalltooth sand tiger or bumpytail ragged-tooth (Odontaspis ferox Risso, 1810) is a species of shark belonging to the Odontaspididae family.
Systematics –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Phylum Chordata,
Chondrichthyes class,
Subclass Elasmobranchii,
Order Lamniformes,
Odontaspididae family,
Genus Odontaspis,
Species O. ferox.
The terms are synonyms:
– Carcharias ferox (Risso, 1810);
– Odontaspis herbsti Whitley, 1950;
– Squalus ferox Risso, 1810.
Geographic Distribution and Habitat –
Odontaspis ferox is a worldwide shark, indicating a possible circumtropical distribution. In the eastern Atlantic Ocean, it is known from the Bay of Biscay south to Morocco, including the Mediterranean Sea, the Azores and the Canary Islands. In the western Atlantic, it has been reported off North Carolina and Florida (USA), the Yucatan Peninsula (Mexico), and Fernando de Noronha (Brazil). It is found throughout the Indian Ocean, from South Africa, Madagascar and Tanzania in the west to the Maldives and Southwest Indian Ridge in the east. In the North Pacific, it is known off Japan, Hawaii, California, and Colombia, and in the South Pacific, it is known from New Caledonia, eastern Australia, and New Zealand. In New Zealand, this species can be found off the coasts of Bay of Plenty, New Plymouth and Hawkes Bay.
Its marine habitat is typically that of deep waters, where it has been captured up to 880m deep.
It is usually found near the bottom in rocky and boulder-strewn regions on continental shelves and the upper continental slope, as well as around submarine ridges and mountains. The species has been reported near rocky or coral reefs and in the upper layers of the open ocean. In the Mediterranean it is found at depths of less than 250 m and also at depths accessible to divers. The preferred temperature range for this species is 6–20 °C; in warm climates, they are found below the thermocline in colder waters.
Description –
The Odontaspis ferox is a shark with a voluminous body and a long, bulbous and slightly flattened snout which reaches a maximum length of 4.1 m for a maximum weight of 289 kg. There are unconfirmed reports of individuals much larger than Malpelo Island off Colombia.
The eyes are medium sized, with large, round pupils and lack nictitating membranes.
The mouth is large and full of protruding teeth. Each tooth has a tall narrow central cusp flanked by two or three pairs of lateral cusplets. There are approximately 48-56 tooth rows in the upper jaw, and 36-46 tooth rows are found in the lower jaw; the large front teeth in the upper jaw are separated from the lateral teeth by two to five intermediate teeth.
The fins are broad-based and angular in shape. The first dorsal fin is larger than the second and positioned closer to the pectoral fins than the pelvic fins.
The caudal fin is highly asymmetrical with the upper lobe much longer than the lower one. Coloration is gray to gray-brown above and paler below. Juveniles are solid in color with darker fin margins, while adults often have dark spots or blotches that vary widely in pattern, size, and density. Coloration also appears to vary by region, with some Mediterranean individuals displaying a mottled “piebald” pattern.
Biology –
Of the biology of the Odontaspis ferox very little is known also because pregnant females have never been found; little is also known about his behavior.
However, the reproduction is ovoviviparous and the embryos feed on the yolk sac and on the other eggs produced by the mother, so that at each birth there are usually two.
It is not known whether the embryos cannibalize each other as in the gray nurse shark. Size at birth is estimated at 1.0–1.1 m. With few recorded exceptions, juveniles are found in deep water and only adults are present above a depth of 200 m; this may serve to reduce predation on juveniles by large shallow-water predators such as the great white shark (Carcharodon carcharias). Males mature at a length of 2.0–2.5 m and females at a length of 3.0–3.5 m. The faint scarring seen on some individuals may be related to courtship.
Ecological Role –
Odontaspis ferox was originally described as Squalus ferox by French-Italian naturalist Antoine Risso in 1810, based on a specimen from Nice, France. In 1950, Gilbert Percy Whitley described O. herbsti from Australian specimens, separating them from O. ferox on the basis of dentition and absence of spots. Leonard Compagno synonymised the two species in 1984, as subsequently discovered Pacific specimens had blurred Whitley’s distinctive characters.
The specific epithet ferox is Latin for “fierce”. Other common names for this shark include blue nurse shark, ferocious shark, Herbst’s nurse shark, and sand tiger shark.
This shark lives near the bottoms of continental and insular shelves and on upper slopes, but sometimes also in shallow waters. Use the long body cavity and big oily liver to regulate buoyancy.
It is a vigorous swimming shark that can be encountered singly or in aggregations of up to five individuals. Catch records suggest that this species can cover long distances in ocean waters along underwater ridgelines or by “leaping” between seamounts. It has a very large oily liver, which allows it to maintain neutral buoyancy in the water column with minimal effort. At a location called “Shark Point” off Beirut, Lebanon, small groups of these sharks appear each summer on rocky reefs at depths of 30-45m. The same individuals have been documented to return to this site year after year. Their purpose is unknown, speculated to be related to mating. When confronted, these sharks have been observed to freeze, gape, turn, and wag their tails at the perceived threat.
It is an active predator of benthic bony fishes, invertebrates and cartilaginous fishes.
The diet therefore consists of bony bottom-dwelling fish such as redfish (Sebastes spp.), invertebrates such as squid, shrimp and possibly marine isopods, and cartilaginous fish including rays and chimaeras. The largest known prey taken by this species was a 1.3 m long red tip shark (Dalatias licha), found inside the stomach of a 2.9 m long male from New Caledonia.
In contrast to its formidable size and appearance, this shark is harmless, having never been known to be aggressive towards humans.
This shark is caught incidentally with gillnets and bottom trawls and longlines; most catches are in the Mediterranean and off Japan. It is usually discarded when caught, except in Japan, where the meat (although considered much inferior to the gray nurse shark) is consumed and the liver oil is used. The fins, jaws and cartilage are also valuable.
Odontaspis ferox have no known predators, although they are bitten by the sharks Isistius brasiliensis. A known parasite of this species is the tapeworm Lithobothrium gracilis, which infests the shark’s spiral valve gut. The carcass of a 3.7m long female found off Fuerteventura in the Canary Islands contained a number of Simenchelys parasitica within her heart, body cavity and back muscles. Whether the eels contributed to the shark’s death is unknown.
Discoveries since the 1970s of specimens in shallow water have raised urgent conservation concerns, as this species is apparently more vulnerable to human activity than previously believed. At present, there is insufficient data for the International Union for Conservation of Nature to assess the global conservation status of this species. It has been assessed as vulnerable in Australian waters, due to a more than 50% decline in catches off New South Wales since the 1970s. In June 2018, the New Zealand Department of Conservation classified this shark as “Endangered – Naturally Uncommon” with the qualification “Endangered Overseas” under the New Zealand Threat Classification System.
Populations of this species in the Mediterranean are also thought to have declined, due to a combination of habitat degradation, overfishing, pollution and human disturbance.
Odontaspis ferox has been protected by the Australian government since 1984; this came in conjunction with the protection of the gray nurse shark, which had been decimated in Australian waters, so as to avoid any pretensions of confusing one species with another. However, these regulations have proven difficult to enforce.
Guido Bissanti
Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Louisy P., 2016. Guide to the identification of marine fish of Europe and the Mediterranean. Il Castello Editore, Milan.
– Nikiforos G., 2008. Fauna of the Mediterranean. Giunti Editore, Florence.
Photo source:
– https://fishesofaustralia.net.au/home/species/1845