Smalltooth sandtiger shark
Introduction
Smalltooth sandtiger sharks are found in the deep waters of the outer continental shelf and upper continental slope off the North Island and oceanic ridges north of New Zealand.New Zealand status: Native
Conservation status: NZ Threat Classification – Naturally uncommon; IUCN Red List – Critically endangered
Population: Unknown due to natural rarity
Found in: Steep and rocky or sandy and muddy terrain, around seamounts, ridges and in open water
Threats: Commercial fishing and plastics, fishing lines or other rubbish
The smalltooth sand tiger shark (odontaspis ferox) may appear large and daunting. However, their behaviour during encounters with divers indicates they are harmless to humans unless provoked.
All records of this species from New Zealand waters come from the upper North Island and Kermadec Ridge. Divers have also observed them at L’Esperance Rock in the Kermadec Islands, around White Island in Bay of Plenty, and at Monowai Rock north of Gisborne.
Other common names for this shark include Herbst’s nurse, deepwater nurse shark and sand shark.
How to identify smalltooth sand tiger sharks
The smalltooth sand tiger has a bulky body with a long, bulbous and slightly flattened snout. This shark is mostly grey-brown in colour above, with a lighter shade below. It has dusky margins to the dorsal fins and upper margin of the tail.
In New Zealand and Australia, adult sharks often have small, dark blotches scattered on the body. These blotches vary in size and density on each shark, and possibly between sharks from different populations. Although rarely encountered, there are adults with ‘piebald’ features. These sharks are covered in large, irregular patches of white, black, grey and brown.
The smalltooth sand tiger also has large dorsal fins, with the first noticeably bigger than the second. The first dorsal fin starts over or just behind the inner corner of the pectoral fin.
Similarities with the grey nurse shark
The smalltooth sand tiger shark is often mistaken for its shallow water relative, the grey nurse shark (Carcharias taurus).
The grey nurse shark also has dorsal fins similar in size but the first dorsal is located well behind the pectoral fin. The teeth have a long, slender central cusp, with only two small, curved cusplets either side of the base.
More about this species
Range and habitat
The smalltooth sand tiger is patchily distributed throughout most warm temperate and tropical regions of the world. Their reported depth range is from 10 m to at least 883 m. All juveniles less than 150 cm length have been taken below 200 m depth. Adults and larger juveniles have been reported across their entire depth range.
They are found on steep rocky terrain as well as open sandy and muddy bottoms along the margins of the continental shelf and the upper continental slope. They also occur around sea mounts, on oceanic ridges and sometimes in open water.
Usually swimming near the sea bottom, they appear to group together on or near reefs. Photographs of uniquely marked individuals suggest the sharks return to favoured sites each year. Similar to the grey nurse shark.
Beyond our national waters, these sharks are known to occur on the Norfolk and Louisville Ridges.
Diet and foraging
Very little is known about the biology and behaviour of smalltooth sand tigers including their diet.
Animals found in their stomachs include small to moderate sized bottom-dwelling sharks and rays, bony fishes and prawns.
Life history
Size at birth is uncertain but appears to be between 100 – 105 cm total length (TL). The smallest free-living specimen known was 107 cm TL.
Size at maturity is unknown. The available data indicate males mature between 200-250 cm TL, and females between 300-350 cm TL.
Maximum size is at least 425 cm TL and more than 600 kg.
Threats to smalltooth sand tiger sharks
Smalltooth sand tiger sharks are naturally rare and have low resilience to fishing. They are vulnerable to longlines, set nets and trawling. A 25 year research trawl dataset from New South Wales found that there has been a large decline in this species off eastern Australia due to bycatch in commercial fisheries.
There are few reported commercial landings this shark in New Zealand. Anecdotal reports from commercial fishers suggests they were sometimes taken in deepwater gill net in the outer Bay of Plenty.
They are also occasionally reported by scientific observers as bycatch in midwater and bottom trawls for deepwater species such as orange roughy.
Smalltooth sand tigers are classified as critically endangered by the IUCN Red List of Threatened Species.
DOC’s work with smalltooth sand tiger sharks
Smalltooth sand tiger sharks are protected under the Wildlife Act 1953. This means it is illegal to hunt, kill or harm smalltooth sand tiger sharks within New Zealand’s national waters (200 nm limit around New Zealand). Any offence under this Act is liable to a fine of up to $250,000 and six months imprisonment.
Fishers and bycatch
It is not illegal to accidentally catch a smalltooth sand tiger but it must be released alive and unharmed. Report the catch to DOC and/or Ministry of Fisheries as soon as possible. DOC may request that dead sharks be landed for scientific research.
Trade in teeth, jaws and fins is illegal
How you can help smalltooth sand tiger sharks
Very little is known of the biology of smalltooth sand tigers. So dead specimens are of considerable scientific value.
Should you inadvertently kill a smalltooth sand tiger notify DOC. We may ask if you can you can bring the shark to shore, if possible. Useful information to provide with the shark includes the location and depth that the fish was taken in.
Other ways you can help:
- When fishing, carefully release any unwanted sharks and rays.
- Do not throw away plastics, nylon fishing line and other types of rubbish at sea. Like whales, large filter-feeding sharks and rays can accidentally eat these, or become entangled in this debris.
- Report sightings or captures to DOC Marine team by emailing sharks@doc.govt.nz or call 0800 DOC HOT (0800 362 468).