PERCENTAGE OF STARVED INDIVIDUALS IN A GROUP AND SIMULATED PREDATION RISK ON THE COLLECTIVE BEHAVIOR OF CHINDONGO DEMASONI

Fish are constantly under a dilemma to balance the behaviors of foraging and predator avoidance in their natural habitats. The present study aimed to investigate the balance between sheltering and foraging activities of fish shoal with different percentages of starved individuals, as well as their response to a simulated predation risk. The Chindongo demasoni, a group living cichlid fish species was selected as an experimental model, and a six-arm radius maze equipped with both shelters and food items was used as an observation arena. The fission-fusion dynamics of fish shoals composed of 8 members with different percentages of starved individuals (8F0S, 7F0S, 4F4S, 1F7S and 0F8S, F represents regularly fed member and S represents starved member) were videoed and analyzed. The main results are as follows (1) Regularly fed fish shoal (i.e., 8F0S) showed higher distribution density in the shelter arm compared to other regions of the maze. However, with the increase of starved member, the distribution density showed a linear increase tendency in the food arm, and there had been no significant difference between in shelter- and food-arms in 0F8S. (2) The grouping frequency in shelter arm decreased with the increased number of starved member, however, none of the variables about fission-fusion dynamics in food arm increased with the increased starved member. (3) Simulated predation risk elicited profound increase in grouping in the shelter arm no matter what the shoal composition is. These results suggested that (1) High priority of behavior strategy in C. demasoni is avoiding predation risk when explored in a novel environment. (2) Shoaling behavior of C. demasoni might be decided by majority of group members rather than minority individuals.