Oryzias pectoralis: how big does it get?

Oryzias pectoralis is a ricefish from the Nakai plateau in central Laos, described by Roberts in 1998 from a rice paddy near Laksao. FishBase gives a maximum of 1 in SL.

Taxonomy & naming

Roberts described the species in 1998 in a revision of the Mekong Oryzias. The name refers to the pectoral fin.

Morphology

A small ricefish; FishBase gives a maximum of 1 in SL.

Habitat

Rice paddies, swamps and sheltered areas of slow-flowing rivers in the Nam Theun basin, central Laos, including the Nakai plateau; FishBase also lists Vietnam.

Feeding

Diet is not documented.

Mating

Courtship has not been described.

Breeding

FishBase reports that egg clusters are deposited among the vegetation. Clutch size and incubation time have not been published.

In the aquarium

Not known in the aquarium trade.

Conservation

The IUCN Red List assessed Oryzias pectoralis as Data Deficient in 2011, meaning there is too little information to judge its extinction risk. The Nakai plateau has been heavily altered by the Nam Theun 2 reservoir.

Common questions

Oryzias pectoralis: how big does it get?: Up to 1 in standard length (SL).
Oryzias pectoralis: where does it come from?: It is recorded from Laos.

On a list: Nano fish

Related species compared · Oryzias

Species	Adult size	Temperature	pH	Hardness	IUCN
Oryzias pectoralisthis species	1 in SL	—	—	—	DD
Songkhram medakaOryzias songkhramensis	0.5 in SL	—	—	—	DD
Mekong medakaOryzias mekongensis	1 in TL	—	—	—	LC
Oryzias haugiangensis	1 in SL	—	—	—	DD
Oryzias hubbsi	1 in SL	—	—	—	NT
Dwarf medakaOryzias minutillus	1 in TL	72–77 °F	pH 7.5–8.5	—	LC
Oryzias chenglongensis	1 in SL	—	—	—	NE
Oryzias moramoensis	1 in SL	—	—	—	NE
Oryzias asinua	1 in SL	—	—	—	EN
Daisy's ricefishOryzias woworae	1 in SL	—	pH 6–7	—	EN
Soeroto's ricefishOryzias soerotoi	1 in SL	—	—	—	CR
Oryzias wolasi	1 in SL	75–79 °F	—	—	DD

Recorded ranges from each species’ own page; hardness is the tolerance its sources give, not a measurement of the water it lives in. See all 40 Oryzias species →

Sources

Naming authority: Oryzias pectoralis in Eschmeyer’s Catalog of Fishes ↗

Last reviewed 2026-10-05.

How to cite

Aquarist Atlas (2026). Oryzias pectoralis. Aquarist Atlas.https://www.aquaristatlas.com/ricefish/oryzias-pectoralis/

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Where it has been recorded

11 georeferenced records (GBIF). Each point is a field observation or museum specimen — pan and zoom to explore where this species turns up. The coordinates come straight from GBIF and are often rounded or tied to the nearest town or river landing, so a dot can sit just beside the actual water rather than in it.

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