Crested bullhead shark
Encyclopedia
The crested bullhead shark (Heterodontus galeatus) is an uncommon species
of bullhead shark
, family
Heterodontidae, occurring off eastern Australia
from the coast to a depth of 93 m (305.1 ft). This shark can be distinguished from other members of its family by the large size of the ridges above its eyes and by its color pattern of large dark blotches. It typically attains a length of 1.2 m (3.9 ft).
Nocturnal and bottom-dwelling, the crested bullhead shark favors rocky reef
s and vegetated areas, where it hunts for sea urchin
s and other small organism
s. It is oviparous, with females producing auger
-shaped egg capsules
that are secured to seaweed
or sponges with long tendrils. Sexual maturation is slow, with one female in captivity not laying eggs until almost 12 years of age. The International Union for Conservation of Nature (IUCN) has assessed this harmless shark as of Least Concern
; it is of no economic interest and suffers minimal mortality from bycatch
, recreational fishing
, and shark net
s.
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. He chose the specific epithet galeatus from the Latin
for "helmeted", referring to the prominent ridges above the shark's eyes that also give it its common name
.
Subsequent authors moved this species to the genera
Gyropleurodus and Molochophrys before placing it in Heterodontus. The type specimen is a 68 cm (26.8 in) long female caught off Australia. This shark may also be referred to as crested shark, crested bull shark, crested horn shark, and crested Port Jackson shark.
, Queensland
to Batemans Bay, New South Wales
. There are also dubious records of this species from off Cape York Peninsula
in the north and Tasmania
in the south. This species 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.
Bottom-dwelling in nature, the crested bullhead shark is found over the continental shelf
from the intertidal zone
to a depth of 93 m (305.1 ft), being more common in deeper waters. It prefers rocky reef
s, mats of seaweed
, and seagrass
beds.
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 membrane
s. The supraorbital ridge
s above the eyes of this species are larger than any other member of its family. The nostrils are separated into incurrent and excurrent openings by a long flap of skin that reaches the mouth. 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. There are deep furrows at the corners of the mouth, extending onto both jaws.
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. The caudal fin is broad, with a strong ventral notch near the tip of the upper lobe. The dermal denticles are large and rough, especially on the flanks. The coloration consists of five brown to black, diffusely edged saddles on a light tan background. There are dark marks on top of the head between the crests and below each eye. Most crested bullhead sharks measure no more than 1.2 m (4 ft) long, but a few may reach 1.5 m (5 ft).
s Centrostephanus rodgersii and Heliocardis erythrogramma, but has also been known to take a variety of other invertebrate
s and small fish
es. A steady diet of sea urchins may stain the teeth of this shark pinkish purple. 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.
Crested bullhead sharks are oviparous with a possibly annual reproductive cycle. Females produce 10–16 eggs per year during late winter in July and August, though Michael (1993) noted that egg laying may continue year-round. The egg cases measure around 11 cm (4.3 in) in length, with a pair of thin flanges spiraling 6–7 times around the outside and two slender tendrils up to 2 m (6.6 ft) long at one end, used to attach the capsule to seaweed or sponges. The capsules are usually deposited at a depth of 20–30 m (65.6–98.4 ft), much deeper than the Port Jackson shark, though there is a single record of an egg being found only 8.6 m (28.2 ft) down. The time to hatching has been variously reported as 5 and 8–9 months; the newly emerged young measure 17–22 cm (6.7–8.7 in) long and resemble the adults. Last and Stevens (1994) gave the lengths at maturity for males and females at 60 cm (23.6 in) and 70 cm (27.6 in) respectively, though mature males as small as 53.5 cm (21.1 in) long were later found off Queensland. Growth and aging has been documented for one captive female at the Taronga Park Aquarium, which grew an average of 5 cm (2 in) per year and did not lay eggs until she was almost 12 years old.
or commercial fisheries
. It is seldom caught on hook-and-line, but is sometimes targeted by spear fishers. Commercial bottom trawl prawn
fisheries operating off Queensland and New South Wales take this species as bycatch
; the impact of these activities on the population is uncertain as this species is not recorded separately from the Port Jackson shark. However, most bullhead sharks caught in these fisheries survive to be released alive. Crested bullhead sharks are likely also caught in mesh shark net
s used to protect beaches; again, most are able to survive the experience. Because of the limited mortality suffered by this species from various human activities, the International Union for Conservation of Nature (IUCN) has assessed this species as of Least Concern
, albeit also recommending that it be carefully monitored given its restricted distribution and overall uncommonness. The range of the crested bullhead shark overlaps with several Marine Protected Areas (MPAs); 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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of bullhead shark
Bullhead shark
The bullhead sharks are a small order of basal modern sharks . There are nine living species in a single genus, Heterodontus, in the family Heterodontidae. All are relatively small, with the largest species being just in adult length...
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Heterodontidae, occurring off eastern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
from the coast to a depth of 93 m (305.1 ft). This shark can be distinguished from other members of its family by the large size of the ridges above its eyes and by its color pattern of large dark blotches. It typically attains a length of 1.2 m (3.9 ft).
Nocturnal and bottom-dwelling, the crested bullhead shark favors rocky reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s and vegetated areas, where it hunts for sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s and other small organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s. It is oviparous, with females producing auger
Auger
An auger is a drilling device, or drill bit, that usually includes a rotating helical screw blade called a "flighting" to act as a screw conveyor to remove the drilled out material...
-shaped egg capsules
Mermaid's purse
An egg case or egg capsule, colloquially known as a mermaid's purse or devil's purse, is a casing that surrounds the fertilized eggs of some sharks, skates, and chimaeras. They are among the common objects which are washed up by the sea. They are made of collagen protein strands...
that are secured to seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
or sponges with long tendrils. Sexual maturation is slow, with one female in captivity not laying eggs until almost 12 years of age. The International Union for Conservation of Nature (IUCN) has assessed this harmless shark as of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
; it is of no economic interest and suffers minimal mortality from bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
, recreational fishing
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
, and shark net
Shark net
A shark net is a submerged net placed around beaches to reduce shark attacks on swimmers.Shark nets do not offer complete protection but work on the principle of "fewer sharks, fewer attacks". They reduce occurrence via shark mortality. Reducing the local shark populations is believed to reduce the...
s.
Taxonomy
BritishBritish people
The British are citizens of the United Kingdom, of the Isle of Man, any of the Channel Islands, or of any of the British overseas territories, and their descendants...
zoologist Albert Günther
Albert C. L. G. Günther
Albert Karl Ludwig Gotthilf Günther FRS, also Albert Charles Lewis Gotthilf Günther , was a German-born British zoologist, ichthyologist, and herpetologist....
originally described the crested bullhead shark as Cestracion galeatus in the 1870 eighth volume of Catalogue of the Fishes in the British Museum. He chose the specific epithet galeatus from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "helmeted", referring to the prominent ridges above the shark's eyes that also give it its common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
.
Subsequent authors moved this species to the genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
Gyropleurodus and Molochophrys before placing it in Heterodontus. The type specimen is a 68 cm (26.8 in) long female caught off Australia. This shark may also be referred to as crested shark, crested bull shark, crested horn shark, and crested Port Jackson shark.
Distribution and habitat
The range of the crested bullhead shark is restricted to the warm temperate waters along the eastern coast of Australia, from Cape MoretonCape Moreton
Cape Moreton is a rocky headland located at the north eastern tip of Moreton Island in South East Queensland, Australia. The surrounding area is part of the Moreton Island National Park. 5 km north-west of Cape Moreton is Flinders Reef....
, Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
to Batemans Bay, New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
. There are also dubious records of this species from off Cape York Peninsula
Cape York Peninsula
Cape York Peninsula is a large remote peninsula located in Far North Queensland at the tip of the state of Queensland, Australia, the largest unspoilt wilderness in northern Australia and one of the last remaining wilderness areas on Earth...
in the north and Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
in the south. This species co-occurs with the related Port Jackson shark
Port Jackson shark
The Port Jackson shark, Heterodontus portusjacksoni, is a nocturnal, oviparous type of bullhead shark of the family Heterodontidae, found in the coastal region of southern Australia, including the waters off Port Jackson. It has a large head with prominent forehead ridges and dark brown...
(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.
Bottom-dwelling in nature, the crested bullhead shark is found over the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
from the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to a depth of 93 m (305.1 ft), being more common in deeper waters. It prefers rocky reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s, mats of seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
, and seagrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
beds.
Description
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s. The supraorbital ridge
Supraorbital ridge
The supraorbital ridge, or brow ridge, refer to a bony ridge located above the eye sockets of all primates. In Homo sapiens sapiens the eyebrows are located on their lower margin.Other terms in use are:* supraorbital arch...
s above the eyes of this species are larger than any other member of its family. The nostrils are separated into incurrent and excurrent openings by a long flap of skin that reaches the mouth. 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
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
-like. There are deep furrows at the corners of the mouth, extending onto both jaws.
The pectoral fins are large and rounded, while the pelvic and anal fins are smaller and more angular. The first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
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. The caudal fin is broad, with a strong ventral notch near the tip of the upper lobe. The dermal denticles are large and rough, especially on the flanks. The coloration consists of five brown to black, diffusely edged saddles on a light tan background. There are dark marks on top of the head between the crests and below each eye. Most crested bullhead sharks measure no more than 1.2 m (4 ft) long, but a few may reach 1.5 m (5 ft).
Biology and ecology
The crested bullhead shark is a slow-moving, nocturnal species often seen wedging its head between rocks in search of food. It feeds primarily on the sea urchinSea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s Centrostephanus rodgersii and Heliocardis erythrogramma, but has also been known to take a variety of other invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and small fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
es. A steady diet of sea urchins may stain the teeth of this shark pinkish purple. 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
Mermaid's purse
An egg case or egg capsule, colloquially known as a mermaid's purse or devil's purse, is a casing that surrounds the fertilized eggs of some sharks, skates, and chimaeras. They are among the common objects which are washed up by the sea. They are made of collagen protein strands...
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.
Crested bullhead sharks are oviparous with a possibly annual reproductive cycle. Females produce 10–16 eggs per year during late winter in July and August, though Michael (1993) noted that egg laying may continue year-round. The egg cases measure around 11 cm (4.3 in) in length, with a pair of thin flanges spiraling 6–7 times around the outside and two slender tendrils up to 2 m (6.6 ft) long at one end, used to attach the capsule to seaweed or sponges. The capsules are usually deposited at a depth of 20–30 m (65.6–98.4 ft), much deeper than the Port Jackson shark, though there is a single record of an egg being found only 8.6 m (28.2 ft) down. The time to hatching has been variously reported as 5 and 8–9 months; the newly emerged young measure 17–22 cm (6.7–8.7 in) long and resemble the adults. Last and Stevens (1994) gave the lengths at maturity for males and females at 60 cm (23.6 in) and 70 cm (27.6 in) respectively, though mature males as small as 53.5 cm (21.1 in) long were later found off Queensland. Growth and aging has been documented for one captive female at the Taronga Park Aquarium, which grew an average of 5 cm (2 in) per year and did not lay eggs until she was almost 12 years old.
Human interactions
Innocuous towards humans, the crested bullhead shark is of little interest to recreationalRecreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
or commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
. It is seldom caught on hook-and-line, but is sometimes targeted by spear fishers. Commercial bottom trawl prawn
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
fisheries operating off Queensland and New South Wales take this species as bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
; the impact of these activities on the population is uncertain as this species is not recorded separately from the Port Jackson shark. However, most bullhead sharks caught in these fisheries survive to be released alive. Crested bullhead sharks are likely also caught in mesh shark net
Shark net
A shark net is a submerged net placed around beaches to reduce shark attacks on swimmers.Shark nets do not offer complete protection but work on the principle of "fewer sharks, fewer attacks". They reduce occurrence via shark mortality. Reducing the local shark populations is believed to reduce the...
s used to protect beaches; again, most are able to survive the experience. Because of the limited mortality suffered by this species from various human activities, the International Union for Conservation of Nature (IUCN) has assessed this species as of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
, albeit also recommending that it be carefully monitored given its restricted distribution and overall uncommonness. The range of the crested bullhead shark overlaps with several Marine Protected Areas (MPAs); 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.