Effects of pre-experimental fasting and sheltering on the swimming performance and oxygen consumption of juvenile grass carp (Ctenopharyngodon idella).

This study investigated the effects of pre-experimental fasting for 2, 7, and 14 days under both unsheltered (12 h dark-12 h light) and sheltered conditions on the critical swimming speed (U_crit) and oxygen consumption (MO₂) of juvenile grass carp, using a modified swim respirometer. Key findings include (1) the U_crit of test fish decreased significantly, by 28%, after fasting for 14 days and sheltering intensified the impact to a 43% decrease, and (2) fish anaerobic capacity decreased after 7 days but increased after 14 days, and was enhanced by sheltering conditions. These findings are important as they indicate that fasting and sheltering can impair grass carp survival and disrupt river ecosystem balance, highlighting the need for habitat conservation.