Abstract: To investigate the effect of starvation on swimming performance of juvenile crucian carp (Carassius carassius), three different measures of swimming performance (critical swimming speed, U_crit; constant acceleration speed, U_cat; maximum speed in faststart, U_fast) were measured after different periods of starvation (1, 14 and 28 days) at 20 ℃. The U_cat was 131%-152% that of U_crit whereas U_fast was 368%-509% that of U_crit with starvation. Starvation showed no significant effect on U_fast whereas significant decreases of 14%-32% in U_cat and of 24%-29% in U_crit were observed after 14 and 28 days of starvation. The difference between U_fast and U_crit(or U_cat) was aggravated after starvation. The difference between U_crit and U_cat was also aggravated after shortterm starvation (14 days) since U_crit was more sensitive to starvation than U_crat. Starvation showed no significant difference in active oxygen consumption rate (MO_2active), indicating oxygen  uptake capacity was not the reason for decrease in U_crit after starvation. Furthermore, starved crucain carp showed higher MO₂ at any given swimming speed and more profound MO₂ increase with the increase of swimming speed compared to fish in control group, indicating that the decrease of U_crit under starvation was mainly due to lower swimming efficiency and shortage of substrates.

Key words: stable isotope, food web structure, wetland ecosystem, trophic relationship, food source