Epaulette Shark

## About

An epaulette shark.

The epaulette shark ***(Hemiscyllium ocellatum)*** also known as the walking shark, is a species of carpet shark endemic to the Great Barrier Reef and Australasia. It is named for the large black spot with a light marginal ring that is located above its pectoral fins, the name 'epaulette' referring to the ornamental shoulder guard of the same name. The Epaulette shark is yellow or tan in colour and is spontaneously spotted with dark brown and black spots. its eyes are placed high on either side of the shark's head and typically have olive green irises and black slit pupils. The pectoral and pelvic fins are rounded with a white trim and are also rather flexible. The fins across the shark's dorsum such as the first and second dorsal fins, are much more typical of shark species, as they are pointed in a triangular shape. Epaulette sharks have slender, rounded snouts and heads, they also possess small whiskers. The species is also classed as a long-tailed carpet sharks and has a narrow body and slender tail. Epaulette sharks can measure only up to 70-90cm (27-35in).

## Diet

As almost all shark species, the epaulette shark is a carnivore and hunts a variety of worm, shrimp, crab, amphipod and small fish species. they use the advantages of electroreception and their sense of smell in order to hunt in a night setting, as they have a nocturnal lifestyle. Epaulette sharks rarely chew their prey, preferring to swallow it whole, unless too large.

## Conservation Status

Epaulette sharks are classed as least concern by the IUCN however, they still face threats to their population. In Australian waters, the impact of the aquarium trade, bycatch and harmful fishing effects are minimised due to low traffic however, in New Guinea, these threats become much more damaging to the epaulette shark. As the New Guinea population of the epaulette shark is considered a subpopulation, the species' threats are considered to be at different severities among the native population. In the New Guinea subpopulation, the epaulette shark is subjected more to the dangers of overfishing and other destructive fishing habits such as bycatch. This subpopulation is also likely threatened heavily by habitat modification and pollution. Dynamite fishing is a popular practice in much of New Guinea and it involves the underwater detonation of explosives in order to kill fish. It threatens the epaulette shark population, as the explosions often damage the reefs which they inhabit. This practice can also lead to accidental shark casualties. Due to the Australian epaulette shark population being mostly unaffected by these threats, the species is not classed as globally at risk of extinction.

## Range and Population

Epaulette sharks inhabit the northern, western and eastern coast of Australia and on the entire coast of New Guinea's main Island group. The shark is well distributed throughout the coastlines of every Australian state but Victoria, Tasmania and South Australia. The species' range encompasses almost the entire Great Barrier Reef and remains consistently common in shallow coastal areas. It has been recorded as far South as Sydney, New South Wales. Epaulette sharks are much more active in shallow or low water-level areas. They can often be found foraging and hunting in shallow coral reefs and flats in a depth of up to only 15cm (5.9in). When the tide goes out, epaulette sharks are often stranded on the upper-most branches of coral trees. The population of the species is unknown however, it is likely in decline.

## Behaviour

Epaulette sharks are active hunters during the day however, they show a preference to hunting around dusk or twilight. They also have a preference for hiding completely or partially underneath coral heads and other over-hanging undersea structures. Uncommonly, they may also lay dormant in open areas, such as sandy flats. Due to the species' shallow-water range, epaulette sharks often get stranded without water for extended amounts of time, once the tide recedes. Though a prolonged stranding would typically cause most fish species to perish, the epaulette shark has evolved the ability to survive without water for up to over three hours, even in areas where the oxygen level is only at 5%. In order to do this, epaulette sharks shut off much of their brain, allowing for less necessary oxygen intake. Once stranded, the epaulette shark attempts to stay in the low oxygen tide pools in-between coral branches however, if this is not possible, it will begin using its paddle-shaped fins to walk across the branches, in a fashion described to be similar to that of a salamander. They have also been known to favour this form of locomotion, even walking on the sea floor as opposed to swimming. Mating season begins during July and continues until December. Females will initially initiate copulation and the male will stabilise the pair during the process by grasping onto any of the female's pectoral fins, or another area close to her gills. The female will lay 2 eggs every 14 days throughout August-December. A female may lay anywhere from 20-50 eggs yearly. The pups will emerge after 120-130 days and will only measure to 14-16cm (5.51-6.2in) after hatching. In order to stabilise themselves, the eggs of the epaulette shark are equipped with fibrous attachments which aim to grasp onto corals and similar environments.

### Relationship with Humans

Epaulette sharks are largely unresponsive to human interaction. They typically allow onlookers to get close before swimming away and will only attack when handled, usually biting at a force which is not painful. The species should be treated as harmless. As the epaulette shark is extremely favourable of shallow waters, they are often sighted as easily observed and they attract attention from tourists for their odd evolutionary attributes. Epaulette sharks have also been known to be kept as pets internationally. They are very unconventional animals and according to reefs.com, epaulette sharks are best kept at a juvenile state however, they grow quickly and it is advised that the average aquarist should provide a larger aquarium as they grow.

## In Captivity

Epaulette sharks are favoured by some groups in the exotic pet community for their strange attributes. They are also housed professionally across the world in institutes such as Tennessee Aquarium and Aquarium of the Pacific in the U.S, Zoo Zürich, Germany and Bristol Zoo, U.K. The only documented case of parthenogenesis in epaulette sharks also occurred in captivity at the Brookfield Zoo, Chicago, where a female epaulette shark gave birth to an exact genetic copy of herself without any sexual stimulation.

## Sources

* IUCN Red List of Threatened Species - https://www.iucnredlist.org/species/41818/68625284
* Epaulette Shark | Australian Museum - https://australian.museum/learn/animals/fishes/epaulette-shark-hemiscyllium-ocellatum/
* Epaulette Shark | Shark Guardian - https://www.sharkguardian.org/post/epaulette-shark
* Epaulette Shark | Aquarium of the Pacific - https://www.aquariumofpacific.org/onlinelearningcenter/species/epaulette\_shark
* Aquarium Fish: The Epaulette Sharks - Perfect Aquarium Sharks | reefs.com - https://reefs.com/magazine/aquarium-fish-the-epaulette-sharks-hemiscyllium-spp-the-perfect-aquarium-sharks/