The Crested Bullhead shark (Heterodontus galeatus) is an uncommon species of Bullhead shark, belonging to the family Heterodontidae. It lives off the coast of eastern Australia. The high ridges above the eyes and the dark patterned blotches of the Crested Bullhead shark are its most distinctive features and helps to identify this shark from other members of its family.
Family: Heterodontidae – Bullhead Sharks
Common Name– Bullhead Sharks
Common Name– Bullhead Sharks
Status: IUCN Red List LEAST CONCERN
Average Size and Length: They are born between 7-8.7 inches. Mature males have been measured between 1.8-2 feet and mature females around 2.3 feet. The longest recorded has been measured at 5 feet.
Current Rare Mythical Sightings: British zoologist Albert Günther originally described the Crested Bullhead shark as Cestracion galeatus in the 1870 eighth volume of Catalogue of the Fishes in the British Museum. Subsequent authors moved this species to the genera Gyropleurodus and Molochophrys before placing it in Heterodontus. The type specimen is a 68-cm-long female caught off Australia. The Crested Bullhead shark may also be referred to as Crested shark, Crested Bull shark, Crested Horn shark, and Crested Port Jackson shark.
Teeth and Jaw: A furrow encircles the incurrent opening and another furrow runs from the excurrent opening to the mouth, which is located nearly at the tip of the snout. The teeth at the front of the jaws are small and pointed with a central cusp and two lateral cusplets, while those at the back of the jaws are wide and molar-like. The deep furrows at the corners of the mouth extend onto both jaws.
Head: The head of the Crested Bullhead shark is short and wide, with a blunt, pig-like snout. The eyes are placed high on the head and lack nictitating membranes. The supraorbital ridges above the eyes of this species are larger than any other member of its family. The Crested Bullhead shark has extremely high and short eye ridges. The depth between the ridges is about equal to the eye length. These high eye ridges are its most distinctive feature. There is a dark bar between the eyes and a broad, dark blotch under the eyes. The nostrils are separated into incurrent and excurrent openings by a long flap of skin that reaches the mouth.
Denticles: The dermal denticles are large and rough, especially on the flanks.
Tail: The caudal fin is broad, with a strong ventral notch near the tip of the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: The Crested Bullhead shark can be found in eastern Australia from southern Queensland to New South Wales. They can be found in the intertidal zone to 305 feet, but are more common in the deeper limits of its range. They can be found on seagrass beds, rocky reefs and in seaweed in warm, temperate waters.
The Crested Bullhead shark co-occurs with the related Port Jackson shark (H. portusjacksoni) across much of its range, but is generally much rarer except off southern Queensland and northern New South Wales, where it tends to replace the other species.
Diet: They mainly eat sea urchins, crustaceans, mollusks and some small fish. It is often seen wedging itself in between cervices and rocks searching for its favorite food. Like some of its family members, the Crested Bullhead shark may have colorful stained teeth due to its steady diet of sea urchins.
The Crested Bullhead shark is also a major predator of the eggs of the Port Jackson shark, which are seasonally available and rich in nutrients.
Ram-Suction Index: The Crested Bullhead shark captures prey with suction, created by expanding its buccal cavity. Its labial cartilages are modified so that the mouth can form a tube, facilitating the suction force. Once the prey is drawn into the mouth, it is secured with the sharp front teeth and then ground into pieces by the flat lateral teeth.
Aesthetic Identification: The Crested Bullhead shark is light-brown to yellow-brown. They have dark, broad bands or saddles. There are no light or dark spots. The pectoral fins are large and rounded, while the pelvic and anal fins are smaller and more angular. The first dorsal fin is moderately tall with a rounded to angular apex and a stout spine on the leading margin, originating behind the pectoral fins. The second dorsal fin resembles the first and is almost as large, and is located between the pelvic and anal fins.
Biology and Reproduction: The Crested Bullhead shark is oviparous. They lay 10-16 eggs per year in seaweed or sponges during the winter. The eggs hatch 5-8 months later. They are thought to have an annual reproduction cycle. Some researchers have observed the Crested Bullhead shark laying eggs year-round.
The egg case is auger shaped, and has two flanges spiraling around it and may take the female several hours to deposit. At first the case is soft and light brown, and over a few days it hardens and darkens in color. The egg case of the Crested Bullhead shark has distinctive, long tendrils at one end. The egg cases measure around 4.3 inches in length. The egg cases are usually deposited at a depth of 66–98 feet, which is much deeper than the Port Jackson shark, though there is a single record of an egg being found only 28 feet down.
Research suggests that sexual maturation is slow, with one female in captivity growing only 2 inches per year and not laying eggs until almost 12 years of age. Last and Stevens (1994) gave the lengths at maturity for males and females at 24 inches and 28 inches, respectively, though mature males as small as 21.1 inches long were later found off Queensland.
Behavioral Traits, Sensing and Intelligence: Like other members of its family, the Crested Bullhead shark is thought to be nocturnal.
The behavior of the Crested Bullhead shark is unique to that of other sharks in its family. The Crested Bullhead shark is also a major predator of the eggs of the Port Jackson shark, which are seasonally available and rich in nutrients. Individual sharks have been observed taking the egg capsules in their mouths and chewing on the tough casing, rupturing it and allowing the contents to be sucked out; egg capsules may also be swallowed whole. Unlike the Port Jackson shark, the crested bullhead shark is not known to form large aggregations. The Crested Bullhead shark looks very similar to the Port Jackson shark; nature has given it the perfect disguise.
Speed: The crested Bullhead shark is a slow-moving shark.
Crested Bullhead Shark Future and Conservation: They are not common, but they are of least concern. They are taken as bycatch on occasion by commercial bottom trawl prawn fisheries operating off Queensland and New South Wales and typically released back alive. They can breed in captivity. The range of the Crested Bullhead shark overlaps with several marine protected areas; additionally, it was listed as a declared animal in Schedule 3 of the 1997 Queensland Marine Parks (Moreton Bay) Zoning Plan, which regulates its collection in Moreton Bay Marine Park.