The Darling River hardyhead (''Craterocephalus amniculus'') is a species of

fish Fish are aquatic, craniate, gill-bearing 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. Approximately 95% of li ...

in the family Atherinidae

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. The species name ''amniculus'' is from the Latin meaning a small creek or stream, in reference to the habitat where these fish are often found. ''Craterocephalus amniculus'' is recorded to be vulnerable to becoming an endangered species because of its restricted range, but the threats and information regarding this recording have not been verified or documented.

Description

The Darling River hardyhead is a small, laterally compressed fish that has a slender and elongated body. The large eyes are silvery in colour and it has narrow lips with few teeth in the mouth. The back is a dusky gold colour while it is silvery gold below. There is a dark, silvery stripe that runs the length of the flanks. They attain a maximum length of . This species has two small,

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

which have short bases and with the second positioned directly over the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is forked and the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s are located high on the body while the

has 5–8 rays. It has small scales that infrequently overlap and there is a count of 37–38 along the midlateral with a transverse count of 14–18 scales. Normally there are no scales on top of head, although sometimes small and circular may be present. The mouth is protractile but its gape is restricted by a ligament situated about a third of the way along the mouth.

Distribution

The Darling River hardyhead occurs in the northern section of the Murray-Darling basin where it inhabits the upper

tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage b ...

of the River Darling in the border area between

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

and

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. Within the Murray-Darlin basin this species has been recorded from the Condamine, Peel, Namoi,

Macintyre MacIntyre or McIntyre is a Scottish surname, relating to Clan MacIntyre. Its meaning is "Son of the Carpenter or Wright". The corresponding English name is Wright. People surnamed ''MacIntyre'', ''Macintyre'' * Alasdair MacIntyre, Scottish phil ...

and Cockburn rivers and in Boiling Down and

Warialda Creek Warialda is a town in the North West Slopes region of New South Wales, Australia, in Gwydir Shire. Situated on the banks of Warialda Creek, the town's name means "Place of Wild Honey" in local aboriginal language. At the , Warialda had a populati ...

s. This is a disjunct distribution and the presence of Un-specked hardyheads seems to exclude this species. Where it does occur it is reported to be relatively common. In the catchment of the

Hunter River Hunter River may refer to: *Hunter River (New South Wales), Australia *Hunter River (Western Australia) *Hunter River, New Zealand *Hunter River (Prince Edward Island), Canada **Hunter River, Prince Edward Island, community on Hunter River, Canada ...

the Darling River hardyhead occurs between .

Habitat and biology

The Darling River hardyhead occurs in slow-flowing, clear, shallow rivers and streams or among the aquatic vegetation at the margins of these waters. It will also occur in faster currents such as those that are found where a deeper pool drains. Their life history is almost unknown but small juvenile specimens have been collected in September. It has been reported to occur solitarily or in schools which can be formed of more than fifty fishes. In the Macintyre River, spawning seems to run from September to February. What is known is that they form pairs to spawn and after mating the females lay the eggs among aquatic vegetation. Breeding and spawning occurs in the middle of summer. They are omnivorous with the bulk of their diet consisting of algae and insect larvae but gastropods, small crustaceans, worms and the eggs of fish have all been recorded as being consumed by this species.

Conservation

The Darling River hardyhead is threatened by habitat degradation associated with agriculture and damaging factors include soil erosion, land clearance, the clearing of riverside vegetation, erosion of riverbanks caused by livestock, flood management and water abstraction. It is also threatened by introduced fish species such as mosquitofish ('' Gambusia holbrooki''), goldfish,

common carp The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...

and

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coasta ...

, the latter often stocked.

Taxonomy

The Darling River hardyhead was previously misidentified as ''

Craterocephalus eyresii ''Craterocephalus eyresii'', the Lake Eyre hardyhead, is a species of freshwater silverside from the family Atherinidae which is endemic to the Lake Eyre basin in Australia. Description ''Craterocephalus eyresii'' is a small drab yellowish-grey ...

'' and was not described until 1990 when Lucy Crowley and Walter Ivantsoff published a description of this species from a type locality of Cockburn River, Nemingha, New South Wales. The populations of similar hardyheads in the Hunter catchment have been provisionally assigned to this species but may, on further investigation, prove to be a different species.

References

{{Taxonbar, from=Q4847694 Darling River hardyhead Fish of the Murray-Darling basin Vulnerable fauna of Australia Darling River hardyhead Taxonomy articles created by Polbot