Hainan medaka (Oryzias curvinotus): where does it come from?

Oryzias curvinotus, the Hainan medaka, is a small ricefish of southern China and northern Vietnam, described by Nichols and Pope in 1927 from Hainan Island. FishBase gives a maximum of 1.5 in TL. It tolerates brackish water and is used in laboratory work, but it is seldom seen in the aquarium trade.

Taxonomy & naming

Nichols and Pope described the species in 1927 from Hainan Island, and it now sits in Oryzias; the authority is therefore in parentheses. It is a member of the East Asian medaka group.

Morphology

A small ricefish with the typical medaka profile. FishBase gives a maximum of 1.5 in TL.

Habitat

Paddies, ponds, ditches, slow streams and brackish coastal waters in southern China, including Hainan, and northern Vietnam. FishBase describes it as a freshwater and brackish, benthopelagic, non-migratory fish.

Feeding

Small invertebrates and algae.

Mating

Courtship is typical of Oryzias, with the male following the female.

Breeding

The female carries the egg cluster briefly and then deposits it on plants.

In the aquarium

FishBase describes it as very difficult to maintain in aquaria, and it is rarely traded. It tolerates a range of salinities and does best in slightly brackish water. It needs a lid.

Conservation

The IUCN Red List assessed Oryzias curvinotus as Data Deficient in 2011, meaning there is too little information to judge its extinction risk.

Common questions

Hainan medaka (Oryzias curvinotus): how big does it get?: Up to 1.5 in total length (TL).
Hainan medaka (Oryzias curvinotus): where does it come from?: It is recorded from China and Vietnam.

On a list: Nano fish

Related species compared · Oryzias

Species	Adult size	Temperature	pH	Hardness	IUCN
Hainan medakaOryzias curvinotusthis species	1.5 in TL	—	—	—	DD
Masapi ricefishOryzias hadiatyae	1.5 in SL	—	—	—	VU
Japanese medakaOryzias latipes	1.5 in SL	64–75 °F	pH 7–8	161–339 ppm	LC
Oryzias loxolepis	1.5 in SL	—	—	—	NE
Luzon ricefishOryzias luzonensis	1.5 in TL	—	—	—	EN
Timor ricefishOryzias timorensis	1.5 in TL	—	—	—	CR
Marmorated medakaOryzias marmoratus	1.5 in SL	72–77 °F	pH 7.5–8.5	—	NT
Northern medakaOryzias sakaizumii	1.5 in SL	—	—	—	LC
Oryzias dopingdopingensis	1.5 in SL	—	—	—	NE
Evers' ricefishOryzias eversi	1.5 in SL	—	—	—	NT
Celebes medakaOryzias celebensis	2 in TL	72–86 °F	pH 8–9	—	LC
Javanese ricefishOryzias javanicus	2 in TL	72–77 °F	pH 7.5–8.5	—	LC

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 →

Also from the Hainan

Traccatichthys zispi

Sources

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

Last reviewed 2026-10-05.

How to cite

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

Add this species card to your site

Paste this into a product listing, club page or blog post. It shows this species’ size, water ranges and conservation status, kept current from the atlas, with a link to this page. Free to use; keep the link intact, as it is the attribution. How the card works.

<div data-atlas="species/oryzias-curvinotus"><a href="https://www.aquaristatlas.com/ricefish/oryzias-curvinotus/">Hainan medaka (Oryzias curvinotus) on Aquarist Atlas</a></div>
<script src="https://www.aquaristatlas.com/embed/v1/card.js" async referrerpolicy="no-referrer"></script>

Where it has been recorded

72 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.

← All ricefish