Abstract: To examine whether the swimming performance and metabolic traits of 1-year-old male and female crucian carps (Carassius auratus) during their Ⅲ reproduction phase have differences, the fast-start movement, critical swimming speed (U_crit), rest metabolic rate (MO_2rest), active metabolic rate (MO_2active), and metabolic rate (MO₂) during different swimming speeds were measured at water temperature 20±1 ℃. The U_crit of female and male crucian carps was 6.97±0.22 and 7.29±0.31 BL·s^-1, and the maximum linear velocity during fast-start movement (V_max) was 20.48±0.69 and 20.40±1.09 BL·s^-1, respectively, with no significant differences. The U_crit, V_max, maximum linear acceleration during fast-start movement (a_max), reaction time, migration distance during the first 120 ms of faststart movement, and MO_2rest of female and male crucian carps also had no significant differences. However, the MO_2active and metabolic scope of female crucian carps were significantly higher than those of the males (341.92±22.59 vs. 307.50±22.66 mg O₂·kg^-1·h^-1 and 257.18±18.51 vs. 220.20±18.95 mg O₂·kg^-1·h^-1, respectively). It was suggested that the male and female crucian carps during their Ⅲ reproduction phase had no significant difference in the swimming capacity, but the females adopted metabolic up-regulation strategy as a compensation for their increased energy burden due to reproduction status.

Key words: Daycent model, soil organic carbon, management practice, carbon sequestration, soil organic carbon change.