In this study, the complete foxl2 complementary (c)DNA sequence was isolated by simple modular-architecture research tool (SMART)er rapid amplification of cDNA ends (RACE). Two year-old female spotted scat, Scatophagus argus, were reared at different temperatures (23, 26 and 29° C) for 6 weeks, or fed with different concentrations of dietary fish oil (0, 2 or 6%) for 8 weeks. Ovarian development, serum oestradiol-17β ( E2) levels, as well as ovarian foxl2 expression were measured. At the end of experiment, ovarian foxl2 messenger (m)RNA expression in fish reared at 23 and 26° C was significantly higher than that in fish reared at 29° C, and that in 2 and 6% fish oil groups was also significantly higher than that in control group ( P < 0·05). Serum E2 levels exhibited the same trend with foxl2 mRNA expression in temperature treatment groups and fish oil fed groups. There was a significant positive correlation between stage of oocytes and foxl2 expressions. Results showed that from 23 to 29° C, the optimal temperature for ovarian development in S. argus was 23-26° C, and 6% fish oil supplementation could effectively promote ovarian development. Optimal temperature and fish oil supplement might increase ovarian foxl2 mRNA expressions to promote ovarian development in S. argus. [ABSTRACT FROM AUTHOR]