The influence of visual and chemical stimuli from cod Gadus morhua on the distribution of two-spotted goby Gobiusculus flavescens (Fabricius)

Detection of a potential predation risk and its influence on patch choice was measured by examining the spatial distribution of 10 two-spotted gobies Gobiusculus flavescens (FABRICIUS) between two feeders, at one of which the presence of a predator was introduced either visually, chemically or both visually and chemically. Without predation influence the gobies were distributed according to the Ideal Free Distribution (IFD). However, as the chemical and /or visual stimulus from a predator cod (Gadus morhua L.) was introduced together with the food at one of the feeding sites, the gobies avoided the affected site. The avoidance persisted during feeding sessions for 1 or 2 days after the introduction. Although image had the most pronounced effect at the time of introduction, odor had a stronger effect on the gobies persistence in avoiding the affected site. Introduction of odor from an injured conspecific (alarm substance) at one of the feeding sites, had no significant influence on the gobies' distribution.