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Nannoperca pygmaea

Morgan, Beatty & Adams, 2013

Little Pygmy Perch

Species Summary

Described as recently as 2013 from just 15 specimens collected in the Hay River system of south-western Australia, Nannoperca pygmaea was for quite a while thought to have one of the most restricted ranges of any Australian fish — known from an area of only about 0.06 km², mostly a handful of pools. More extensive survey work and genetic assessment since then have turned up additional small fragmented populations across the Hay, Mitchell, Kent, Denmark, Walpole and Deep Rivers, and Lake Smith, considerably broadening its known range. It nonetheless remains listed as Endangered under both the federal Environment Protection and Biodiversity Conservation Act and the Western Australian Biodiversity Conservation Act.

Distribution & Habitat

Genetic sampling has verified an additional population at Lake Smith, in the Donnelly River Basin, well separated from the species’ other known sites further east around the Kent and Denmark River Basins. The limited genetic difference between these far-flung populations suggests Nannoperca pygmaea once had a considerably broader historic distribution than it does today, with dispersal opportunities between them likely lost only as human-mediated landscape change fragmented the region’s waterways.

Description

Differs from its close, range-sharing relative Nannoperca vittata (Western Pygmy Perch) in lacking dark pigment on the ventral surface in front of the anus, in having thin latero-ventral stripes, generally fewer dorsal and anal fin rays, unpigmented scale margins on the caudal peduncle, and a more strongly haloed dark spot at the base of the tail fin. Allozyme analysis confirms Nannoperca pygmaea and N. vittata belong to genetically distinct lineages with no intermediates where they occur together, distinguished by fixed differences at fifteen separate genetic loci.

Taxonomy

A comprehensive 2025 genetic survey found Nannoperca pygmaea to be sister to an undescribed form of Nannoperca vittata restricted to the Shannon River Basin — the two together forming a distinct evolutionary lineage separate from the rest of the Western Pygmy Perch complex. A full taxonomic revision, re-diagnosing both species properly, is still pending.

Compiled for Home of the Rainbowfish from ANGFA sources: D. L. Morgan, S. J. Beatty & M. Adams, “Nannoperca pygmaea, a New Species of Pygmy Perch (Teleostei: Percichthyidae) from Western Australia”, In-Stream 22(6), June 2013, p. 19 (summarising Zootaxa 3637(4): 401–411).

References