Male and female Humpback Blackdevils look very different. Females have a large head and mouth, with long pointed teeth. They grow to 18 cm in length. Males, however, are slender fish that lack a lure and only grow to 2.9 cm.
The Humpback Blackdevil is a soft-bodied fish that lacks scales and pelvic fins. Females have a large head and mouth, with long pointed teeth. There is a short illicium with a bulbous esca on the snout. Live fish are black.
Two species of Melanocetus occur in Australian waters. The second is Murray's Abyssal Anglerfish, Melanocetus murrayi. Females can be distinguished by the shape of the anterior margin of the vomer (nearly straight in M. johnsonii vs deeply concave in M. murrayi) and size and shape of the escal bulb. Males can be distinguished by the number of denticular teeth on the snout and lower jaw (11 or more and 12 - 24 respectively for M. johnsonii vs 3 - 5 and 10 - 13 for M. murrayi) and the number of dorsal and pectoral fin rays (13 - 15 and 17 - 20 for M. johnsonii vs 12 - 14 and 15 - 18 for M. murrayi).
It occurs at mesopelagic depths in tropical and temperate waters worldwide. In Australia it is known from off central to southern New South Wales and near Norfolk Island.
The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Source: Atlas of Living Australia.
Ozcam map of Humpback Blackdevil specimens in the Australian Museums. http://ozcam.ala.org.au/occurrences/search?q=melanocetus%20johnsonii&zoom=off#mapView
- Bertelsen, E., & Pietsch, T.W. 1983. The Ceratioid Anglerfishes of Australia. Records of the Australian Museum. 35: 77-99.
- Pietsch, T. W. 1999. Melanocetidae. in Carpenter, K.E. & V.H. Niem (Eds). FAO Species Identification Guide for Fishery Purposes. The Living Marine Resources of the Western Central Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae). FAO, Rome. Pp. iii-vi, 1398-2068.
- Stewart, A.L. & T.W. Pietsch. 1998. The ceratioid anglerfishes (Lophiiformes: Ceratioidei) of New Zealand. Journal of the Royal Society of New Zealand. 28 (1): 1-37.