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Cryptic carp gudgeon

Other common name(s): 
Scientific name: 
Hypseleotris acropinna
Thacker, Geiger & Unmack, 2022
Michael Hammer
Threatened but recovering


Part of the complex of the sexual species (Cryptic) and hemiclones (between Bald and Cryptic and Boofhead and Cryptic) previously known as Murray-Darling carp gudgeon.  

The common name ‘cryptic’ refers to the difficulty in distinguishing this species from its hemiclone with Boofhead carp gudgeon; its long confusion with Boofhead in the Murray-Darling Basin; and Cryptic carp gudgeon not being recognized as a species despite it being common and widespread.

Like all carp gudgeons, a small and laterally compressed species, with a truncate to slightly rounded tail, and small, upturned mouth. Generally, around 25-40 mm length, but can reach 60 mm. The head is pointed, with a V-shaped snout profile, unlike the rounder profiles of Boofhead and Bald carp gudgeons. Generally, a pale body colouration overall with dark-edged scales; dark scale margins more intense on middle of sides (but not as prominent as in Western carp gudgeon). Fins are clear except in breeding males which have pale orange bands along the edge of the second dorsal and anal fins.

Adult males can be distinguished from other carp gudgeons in the MDB by their elongated rays at the rear end of the second dorsal and anal fins, with fin tips extending along the length of the caudal peduncle.  

Biology and Habitat

No specific studies on this species alone (as opposed to studies on generic Hypseleotris spp). Reproductive ecology has been briefly described from aquarium spawning of ‘Murray-Darling carp gudgeon’ which provides a useful guide to what likley occurs with Cryptic carp gudgeon.  Aquarium spawning’s have occurred from December at water temperatures of 20–24 °C. Around 500 eggs were laid, hatching in 4–5 days, with fry ~4 mm length on hatching. Dietary ecology is unstudied but is expected to be similar to other carp gudgeons. Cryptic carp gudgeom is most closely related to the coastal Firetail gudgeon (H. galii) and aspects of Cryptic's biology is likely similar to Firetails.

Distribution and Abundance

Found patchily throughout the MDB as well as some eastern coastal streams in Qld. Introduced populations are also present in several coastal catchments in Victoria and South Australia.  

Cryptic carp gudgeon is widely recorded from parts of the Condamine, Dumaresq, Severn (NSW), Castlereagh, Macquarie, Bogan, rarely in the lower Lachlan and Murrumbidgee, but more commonly in the Murray River from Albury downstream through SA, plus in Vic in the Keiwa, Ovens, Broken and Goulburn rivers.

The distribution map only shows confirmed genetic records of this species (no hemiclones or unverified records). Records of this newly described species would also be included within the general ‘carp gudgeon’ map, but the taxonomic confusion means that these records cannot be separated out.  

Potential Threats

None known. Predation by alien fish such as Redfin perch in floodplain ponds/billabongs can significantly reduce local abundance.

General References

Bertozzi et al. 2000; Thacker et al. 2022; Unmack 2000, Unmack et al. 2019.

This species account is an extract from Fishes of the Murray-Darling Basin (second edition) and should be cited as "Lintermans, M. 2023, Fishes of the Murray–Darling Basin, Australian River Restoration Centre, Canberra."

Other Fish in this family

Front book cover of Fishes of the Murray–Darling Basin

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The second edition of Fishes of the Murray-Darling Basin by Mark Lintermans is available now! This edition has been fully revised, incorporating new ecological knowledge on each species and additional species accounts.

Fishes of the Murray-Darling Basin remains the only book of its kind, devoted exclusively to the fishes of Australia’s largest river system, containing rigorous information on the identification, habitats, biology and distribution of the freshwater fish of the Murray-Darling Basin, as well as background information on the threats to fish and aquatic ecosystems. It is an invaluable resource for naturalists, students, fishers, scientists and anyone else interested in the life within our rivers.

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