NUTRITIONAL STATUS AND AEROBIC SCOPE ON GROUP BEHAVIOUR OF JUVENILE GOLDFISH (CARASSIUS AURATUS)

In order to investigate the effects of nutritional status and metabolic range on group behavior of fish, juvenile crucian carp (Carassius auratus) was conducted as the animal model, and its feeding metabolism (specific dynamics, SDA) and metabolic rates (Standard Metabolic Rate, SMR; Maximum Metabolic Rate, MMR) was determined to calculate metabolic scope (AS=MMR–SMR) at (25.4±0.2)℃. Based on the combination of nutritional state and AS, five ‘nutritional state plus AS’ treatments were determined for their individual spatial position within a group, feeding intake, individual characteristics (e.g., individual swimming speed and acceleration), and group characteristics (e.g., synchronization of speed, inter-individual distance, nearest neighbour distance, and group polarization). Our results showed that nutritional status, starvation, aerobic scope, feeding and digestion had no effect on individual spatial position within a group. Starvation and digestion did not affect the group cohesiveness of juvenile crucian carp, but starvation reduced the group coordination of this species only during digestion, i.e., difference in individual food acquisition ability led to a different digestion strategy among group-mates, resulting in a lower synchronization of speed and eventually a decrease in group coordination. In the control group, the space in the front of the group confers the ecological advantage of individuals to obtain more food items, but starvation eliminated this ecological advantage in the front of the group. The feeding intake and feeding level of the control group were negatively correlated with the predicted remaining AS, and which of the starvation group were not correlated with the predicted remaining AS. Our results suggested that both the nutritional status and aerobic scope had no effect on the individual spatial position within schooling in gold fish. Occupying the spatial position at the front of the school can confer to the ecological benefits (e.g., more food resources), but starvation eliminates the heterogeneity of ecological benefits of individual spatial position distribution within the school. Starvation and digestion have no effect on group cohesion of the goldfish, but the phenomenon that starvation reduces the group coordination only appeared during the digestion stage. Individual difference in ability to obtain food within the group may lead to different digestive strategies among group-mates, resulting in more disordered swimming align of individuals, and finally leads to the decline of group coordination.