Yarra Pygmy Perch, Nannoperca obscura (Klunzinger 1872)

Summary:

A small dusky, pale brownish-grey or olive-green pygmy perch becoming pale below, with darker chevron-shaped markings on the rear of the body, transparent to pale yellowish to blackish fins, and a pupil that is somewhat oblong. The Yarra Pygmy Perch differs from other Nannoperca species in having the pre-orbital bone not completely covered by skin, exposing its serrated lower edge.

The species was described from the 'Yarra Lagoon, near Melbourne'. Unfortunately, Yarra Pygmy Perch are now extinct in the Yarra River.

Cite this page as:

Bray, D.J. & Thompson, V.J. 2022, Nannoperca obscura in Fishes of Australia, accessed 25 Apr 2024, https://fishesofaustralia.net.au/Home/species/4459

Yarra Pygmy Perch, Nannoperca obscura (Klunzinger 1872)

More Info

Distribution	Endemic to temperate waters of the Bunyip River system, Victoria, westwards to the Finniss River, Bool Lagoon and Lake Alexandrina in eastern South Australia. Populations that once inhabited the Yarra River and Dandenong Creek near Melbourne, are now presumed extinct. Remaining populations have become fragmented due to water regulation and habitat loss. Typically inhabits slow-flowing to still waters with abundant submerged and emergent aquatic vegetation, and often woody debris - such as lakes, ponds, , along with pools in slow to moderately high-flowing rivers and streams.
Features	Dorsal fin VIII-IX, 7-9 (usually IX, 9); Anal fin III, 6-7; Pectoral fin 11-13 (usually 12). Body oblong, compressed; dorsal profile more strongly arched than ventral profile; head large, dorsal profile straight; snout pointed; eye of moderate size, dorsolateral; mouth small, terminal, slightly oblique, protractile; jaw reaches back to front of eye; jaws, vomer and palatines with narrow bands of villiform teeth; lower, free edge of preorbital bone straight, strongly serrated; numerous distinct pores on head and operculum. Scales moderately-large, finely ctenoid without circular ridges; scales present on head, opercula and cheeks; lateral line of interrupted series of tubed scales; mid-lateral scales 28-30; transverse scale rows 12-13. A single dorsal fin with an anterior spiny section and posterior soft section separated by deep notch; anal fin opposite and similar to soft part of dorsal fin; pectoral fins small, rounded, positioned low on sides; ventral fins small, pointed, set well forward on abdomen; caudal fin moderately large, truncate or rounded.
Size	To 7.5 cm SL, commonly to 5cm.
Colour	Olive green above, greenish-brown laterally, yellowish-white below, with darker scale margins and a faint reticulate pattern. Opercular region with golden sheen. Several dark blotches mid-laterally. Fins clear, fawn to orange, often with dark margins; pelvic and anal fins often with dark anterior edge. Caudal peduncle with a dark spot. Prior to spawning, the pelvic fins of the male become black, the leading edge of the anal fin darkens and the dorsal and anal fins become an intense brownish-orange.
Feeding	Feeds mostly on insects, insect larvae and planktonic crustaceans. The species may also consume small molluscs.
Biology	Little is known of the biology of this species. Spawning occurs in September to October at water temperatures between 16 and 24°C. Like other pygmy perches, this species presumably spawns large demersal eggs amongst aquatic vegetation. The species is short-lived, with individuals living less than 5 years.
Conservation	IUCN Red List: Endangered EPBC Act 1999: Vulnerable Victorian Flora and Fauna Guarantee Act 1988: Threatened Populations of Yarra Pygmy Perch have declined in recent decades, due to habitat loss and predation by, and competition with introduced species such as Redfin (Perca fluviatilis) and Brown Trout (Salmo trutta). Major threats include habitat degradation and loss, altered flow regimes; predation by Redfin Perch, Perca fluviatilis, Brown Trout, Salmo trutta and Rainbow Trout, Oncorhynchus mykiss; habitat destruction by Common Carp, and competition and predation by Eastern Gambusia, Gambusia holbrooki; affects of climate change
Remarks	Yarra Pygmy Perch form small shoals, often mixing with Southern Pygmy Perch, Nannoperca australis.
Similar Species	The Yarra Pygmy Perch differs from the Southern Pygmy Perch, Nannoperca australis, in having a smaller mouth, a serrated preorbital bone, and in having a slightly notched pupil rather than one which is round. Fins of breeding males turn black compared with the bright red fins of N. australis.
Etymology	The specific name obscura is from Latin (= darkened) in reference to the dark fins of breeding males.
Species Citation	Paradules obscurus Klunzinger, 1872, Arch. Naturg. 38(1): 20. Type locality: Yarra lagoon, Melbourne, Victoria.
Author	Bray, D.J. & Thompson, V.J. 2022
Resources	Atlas of Living Australia Australian Faunal Directory Catalog of Fishes

Yarra Pygmy Perch, Nannoperca obscura (Klunzinger 1872)

References

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