Temporal changes in body mass, body composition and metabolism of gibel carp Carassius auratus gibelio during food deprivation

To investigate the response to starvation, gibel carp Carassius auratus gibelio [12.5 ± 0.03 g (mean ± SE, n = 24)] were deprived of food at 25.8 ± 0.2°C (mean ± SE, n = 56) for 56 days. Body mass, proximate composition in whole body and muscle, and respiration were measured at 7‐day intervals. Body mass decreased with prolongation of deprivation, with a significant decline recorded after 7 days deprivation. Fish lost 22% of their fresh mass and 34% of dry mass after 56 days. Fish lost 38% of the body lipid over the first 7 days, and lost body lipid at a rate of 0–11% per week over the remaining 49 days. Body protein was lost at 1–5% per week throughout deprivation. Compared with the initial composition, body lipid concentration was lower and ash concentration higher on day 7. Water as a percentage of body mass was higher after 28 days, and protein concentration lower after 42 days, than at the start of deprivation. Muscle lipid and protein concentration was lower, and % water higher, after 7 days than at the start of deprivation, whereas muscle ash concentration was relatively constant during deprivation. After 56 days, fish lost body water by 18%, body lipid by 84%, body protein by 30%, and body energy by 45%. Oxygen consumption rate dropped from day 1 to day 3, increased from day 4 to day 14, gradually decreased from day 15 to day 35, and maintained a relatively constant level from day 36 to day 56. Results of the present experiment reveal that gibel carp utilize body lipid as a major energy source in the first 7 days of food deprivation, then turn to body protein as an energy fuel when lipid reserves are heavily depleted. Oxygen consumption is maintained at a relatively low and constant level when most lipid reserves are exhausted.