Effect of water temperature on reproductive performance and offspring quality of rare minnow, Gobiocypris rarus

Water temperature plays a significant role in the reproductive processes of temperate fishes. In the present study, the effects of water temperature on the reproductive performance and offspring quality of rare minnow (Gobiocypris rarus) were evaluated by cultured parent fish at different temperature (18～30 ℃) in a 2-month trial. The results revealed that rare minnows could spawn continuously within the range from 18 ℃ to 30 ℃, and these at 24 ℃ and 27 ℃ spawned every 3-4 days. Batch size of rare minnow increased with increasing water temperature, while egg production increased with increasing water temperature and then decreased at 30 ℃. High water temperature (30 ℃) had significantly adverse effects on fertilization rate and hatching rate (P<0.05). It was found that the oocyte growth at 18 ℃, 21 ℃, and 30 ℃ were slower than those at 24 ℃ and 27 ℃. Histologic analysis further showed that low temperature (18 ℃ and 21 ℃) slowed down vitellogenesis and oocyte maturation, while high temperature (30 ℃) had suppressive effects on oocyte maturation and ovulation. Based on present results, it was concluded that 24-27 ℃ was optimal breeding temperature for rare minnows and water temperature higher than 30 ℃ resulting from climate change would pose a threat to its wild populations.