Hoplostethus melanopeza Roberts & Gomon 2012


Other Names: New Zealand Giant Sawbelly

A paratype of Hoplostethus melanopeza (NMNZ P.053308, 486 mm SL), from east of Mayor Island, Bay of Plenty, North Island, New Zealand, depth 540 m, March 2012. Source: Carl Struthers / Museum of New Zealand, Te Papa Tongarewa. License: All rights reserved

Summary:
A large rare deepwater roughy found on the continental slope, seamounts and submarine rises off eastern Australia and New Zealand.

 Identifying features:
• Head and body overall dark greyish-red
• Top side of tongue, gill arches and gill cavities black
• Front of mouth including underside of tongue mostly white
• Fins deep red with distinct black margins 

Cite this page as:
Martin F. Gomon, Hoplostethus melanopeza in Fishes of Australia, accessed 14 Jul 2024, https://fishesofaustralia.net.au/home/species/4848

Hoplostethus melanopeza Roberts & Gomon 2012

More Info


Distribution

Sub–tropical and temperate waters of the Tasman and South Fiji Basins in the south–western Pacific, between about 33° and 37°S, from the continental slope off south–eastern Australian on the west, to the outer Bay of Plenty and southern Kermadec Ridge at the north end of the North Island in New Zealand in the east. H. melanopeza occurs on continental slopes, seamounts and submarine rises in depths of 140–760 m, mostly at 250–400 m.

Features

Meristic features:
• Dorsal fin VI-VII, 12-13 (mostly VI, 13)
• Anal fin III, 9-10 (mostly 10)
• Caudal fin 6 + 2 + 9 + 8 + 2 + 6 (7 + 2 + 9 + 8 + 2 + 6 in 2of 21)
• Pectoral fin rays 14-16 (mostly 15)
• Pelvic fin I, 6
• Gill rakers 18-21 (5-6 + 1 + 12–14 = 18–21)
• Lateral–line scales 27 + 1 (26–29 + 1, rarely 2)
• Transverse scales 12/1/25 (9–15/1/20–28; mean 11.1/1/23.4)
• Predorsal scales 16–22
• Abdominal scutes 9-12 (mostly 10)
• Vertebrae 11-15
• Pseudobranch 19 (16-21)
• Branchiostegal rays 8. 

Body ovoid, deep, depth 1.9–2.1 in SL; nape gently curved, forehead almost straight to above upper lip.

Dorsal– and anal–fin spines of moderate thickness.

Scales absent from isthmus; body scales adherent; lateral–line scales with strong medial ridge, but no spine in small and medium sized adults, with strong spine centrally on posterior margin in large adults; scales on predorsal midline forming low raised ridge. 

Size

Reaches at least 515 mm SL.

Colour

Fresh specimens: head and body dark greyish red; opercle dark greyish-red; dark areas of buccal and branchial cavities black; vomer, margins of mouth roof lateral to palatines, underside of tongue and upper surface of lower jaw stark white; fins a deep red with narrow black margins in adults.

In preservative: grey (juveniles pale below a line between humeral spine and dorsal side of caudal peduncle near termination of dorsal fin base, dusky above); opercle dark; buccal and branchial chambers dark, including gill arches and rakers; vomer, roof of mouth lateral to palatines, underside of tongue and lower jaw uniformly pale; fins pale with narrow dark margins (juveniles with pale fins, except for slightly dusky outer portion of membrane between dorsal–fin spines).

Biology

Although nothing is known of the biology of this species, like other deepwater roughies, H. melanopeza is likely to take many years to mature and be very long-lived.

Conservation

  • IUCN Red List: Not Evaluated
  • EPBC Act: Not listed
  • Similar Species

    Hoplostethus melanopeza is very similar to H. gigas, with which it has been confused in the past. Although both species have a similar overall red or reddish–orange colouration, large individuals of H. melanopeza have distinct black margins to all fins, while the edges of only the medial fins appear to be no more than dark grey to blackish in large individuals of H. gigas.

    H. melanopeza also has a greater number of predorsal scales (16–22 versus. 9–15) and a higher mean value for total gill rakers of 19.7 versus 18.0, based on material examined. At comparable sizes H. melanopeza has a slightly deeper body and shorter pelvic to anal–fin length than H. gigas, although additional material of various size ranges is needed for a full comparison.

    Etymology

    The species name melanopeza is from the Greek melano meaning ‘black’ and peza meaning ‘edge’, in reference to the characteristic black edge on all fins in large individuals of this species.

    Species Citation

    Hoplostethus melanopeza Roberts & Gomon 2012, Mem. Mus. Vict. 69: 346, figs 3-4. Type locality: New Zealand, North Island, Bay of Plenty, Mayor Knolls, 12 km east of Mayor Island, 37°19.07' S, 176°25.35' E, 320 m.

    Author

    Martin F. Gomon

    Resources

     

    Hoplostethus melanopeza Roberts & Gomon 2012

    References


    Roberts, C.D. & M.F. Gomon. 2012. A review of giant roughies of the genus Hoplostethus (Beryciformes, Trachichthyidae), with descriptions of two new Australasian species. Memoirs of Museum Victoria 69: 341–354.

    Quick Facts


    Depth:140-760 m

    Habitat:Seamounts, submarine rises

    Max Size:52 cm SL

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