Checkered Perchlet, Plectranthias inermis Randall 1980

Other Names: Geometric Hawkfish, Geometric Perchlet, Geometric Pygmy Hawk, Red Blotched Perchlet

A Chequered Perchlet, Plectranthias inermis, at Ra, Fiji, November 2017, depth 32m. Source: Mark Rosenstein / License: CC By Attribution-NonCommercial-ShareAlike

A perchlet with a red and white checkered pattern on the body that extends onto the posterior abdomen, anal-fin base and caudal peduncle.

Cite this page as:
Bray, D.J. 2021, Plectranthias inermis in Fishes of Australia, accessed 28 May 2023,

Checkered Perchlet, Plectranthias inermis Randall 1980

More Info


Known from the Australian territory of Christmas Island in the Eastern Indian Ocean. Elsewhere the species is widespread in the Indo-West Pacific: from Mauritius to Fiji.
Inhabits deep coastal and inner reef drop-offs, usually sheltering among rubble or in crevices at the base of back-reef steep slopes.


Dorsal fin X, 16-18; Anal fin III, 7; Pectoral fin 13, all rays unbranched; Gill rakers 5-6 + 10-12; Lateral-line incomplete, 12-22 tube scales in anterior series; Vertebrae 10+16.
Third dorsal-fin spine the longest; antrorse spines on lower margin of preopercle absent; upper margin of preopercle not serrate or with only a few isolated weak serrae; 3 prominent flat spines on opercle. Pectoral fins very long, the longest rays reaching posterior to rear base of anal fin.


Fresh colour of holotype: white with large near-quadrangular blotches of orange-red in about three irregular rows on body, the red in the blotches concentrated in a spot on each scale; large blotches of the same color on nape, the largest beginning at origin of dorsal fin and passing two-thirds the distance to eye; small blotches of light red admixed with yellow on ventral half of head; first three membranes of spinous portion of dorsal fin pale yellowish; remaining membranes whitish with an outer row of yellow spots, one per membrane, and red distal tips; an orange-red spot basally on first, fifth, sixth, and eighth to tenth dorsal spines; soft dorsal whitish with pale pink rays and a faint yellowish stripe near base; caudal and anal fins whitish with pink rays, the anal with some yellow on spinous membranes and three orange-red spots at base; pectoral fin, transparent with pinkish rays; pelvic fins whitish on lateral edge with pink rays and a streak of yellow on the last three membranes; iris a mixture of light red and yellow. 

Similar Species

The following combination of characters distinguishes Plectranthias inermis from congeners: segmented dorsal rays 16–18; third dorsal spine longest, 15.6–18.8 % SL; lateral line complete, interrupted or incomplete, consisting of 12–28 tubed scales; predorsal scales extend anteriorly to middle or posterior interorbital (at point ranging from vertical through posterior edge of orbit to vertical through middle of pupil); preopercle with 3–11 weak serrations on posterior (vertical) edge and 0–2 weak serrations on ventral edge (none antrorse).


The specific name is from the Latin inermis (= unarmed), in reference to the lack of spines and serrae on preopercle, the small outer canine teeth of the upper jaw, and lack of canines in the lower jaw.

Species Citation

Plectranthias inermis Randall 1980, Micronesica 16(1): 135, fig. 11. Type locality: Southwestern side of Caban Island, Batangas, Luzon Island, Philippines. 


Bray, D.J. 2021


Atlas of Living Australia

Checkered Perchlet, Plectranthias inermis Randall 1980


Allen, G.R. & Erdmann, M.V. 2012. Reef fishes of the East Indies. Perth : Tropical Reef Research 3 vols, 1260 pp.

Allen, G.R. & Steene, R.C. 1988. Fishes of Christmas Island Indian Ocean. Christmas Island : Christmas Island Natural History Association 197 pp.

Allen, G.R., Steene, R.C. & Orchard, M. 2007. Fishes of Christmas Island. Christmas Island : Christmas Island Natural History Association 2 edn, 284 pp. 

Gill, A.C., Pogonoski, J.J., Moore, G.I. & Johnson, J.W. 2021. Review of Australian species of Plectranthias Bleeker and Selenanthias Tanaka (Teleostei: Serranidae: Anthiadinae), with descriptions of four new species. Zootaxa 4918(1): 1-116.

Heemstra, P.C. 1996. A review of species of the Anthiine fish genus Plectranthias (Perciformes: Serranidae) from Mauritius. Trans. Roy. Soc. S. Afr. 51: 139-146.

Heemstra, P.C. & Randall, J.E. 2009. A review of the anthiine fish genus Plectranthias (Perciformes: Serranidae) of the Western Indian Ocean, with description of a new species, and a key to the species. Smithiana Bulletin 10: 3-17.

Kuiter, R.H. 2004. Basslets, Hamlets and their relatives. A comprehensive guide to selected Serranidae and Plesiopidae. Chorleywood, UK : TMC Publishing 1, 216 pp. 

Kuiter, R.H. & Tonozuka, T. 2001. Indonesian Reef Fishes. Part 1. Eels- Snappers, Muraenidae - Lutjanidae. Australia : Zoonetics pp. 1-302.

Randall, J.E. 1980. Revision of the fish genus Plectranthias (Serranidae: Anthiinae) with description of 13 new species. Micronesia 16(1): 101-187. See ref online

Randall, J.E. 1996. Two new anthiine fishes of the genus Plectranthias (Perciformes: Serranidae), with a key to the species. Micronesica 29(2): 113-131 See ref online

Williams, J.T., Lawrence, A. & Myers, R. 2016. Plectranthias inermis. The IUCN Red List of Threatened Species 2016: e.T69588709A69592432. Downloaded on 07 January 2018.

Quick Facts

CAAB Code:37311201

Conservation:IUCN Least Concern

Depth:14-65 m

Fishing:Aquarium fish

Habitat:Reef associated

Max Size:4.5 cm SL

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