Some fish live in aquatic environments with low or temporally changing $O_2$ availability. Variation in dissolved oxygen (DO) levels requires behavioral, physiological, and biochemical adaptations to ensure the uptake of sufficient $O_2$. Several species are relatively well adapted to tolerate low $O_2$ partial pressures (hypoxia). The medaka (Oryzias dancena ) is an important model organism for biomedical research that shows remarkable tolerance to hypoxia. We investigated the regulation and role of hypoxia-inducible factor-1 (HIF-$1{alpha}$) as a general hypoxia-response gene and stanniocalcin-2 (STC2), which is one of the genes regulated by HIF-$1{alpha}$ in mammals under hypoxia. We subjected adult male medaka to the following three acute hypoxia regimes: 1, 24, and 72 h at DO = $1.8{pm}0.5$ ppm. The changes in STC2 and HIF-$1{alpha}$ mRNA were monitored using quantitative real-time reverse-transcription PCR. We found strong upregulation of HIF-$1{alpha}$ mRNA in the livers of fish exposed to hypoxia. Hypoxia rapidly upregulated STC-2 mRNA expression in muscle, but not in the brain, gills, liver, or intestine. Therefore, unlike in mammals, hypoxia might regulate O. dancena STC-2 expression in an HIF-$1{alpha}$-independent manner.