Response of naive two-spotted gobies Gobiusculus flavescens to visual and chemical stimuli of their natural predator, cod Gadus morhua

In order to determine whether the anti-predator response of gobies to cod Gadus morhua is inherited, naive two-spotted gobies Gobiusculus flavescens were exposed to visual or chemical cod stimuli, in order to determine whether such stimuli would trigger an innate anti-predator response. Groups of 10 naive adult two-spotted gobies were tested for their distribution between 2 habitats in an aquarium: 1 'safe' and 1 'risky' habitat, in which a cod was presented either visually or by its odour. Equal amounts of food were available in the 2 habitats. When no predator stimuli were presented in either habitat, the gobies distributed themselves equally between them both. When a visual stimulus of a cod was presented in 1 of the habitats, they avoided this habitat, The introduction of cod odour in 1 of the habitats did not influence the distribution of the gobies. After a single session with a cod physically present in 1 habitat, the gobies still did not respond to the introduction of cod odour the following day, However, after having experienced a cod being physically present on 3 consecutive feeding sessions, they responded to cod odour with avoidance. The response to cod odour was still significant 6 mo after the experience, It therefore appears that the goby has an innate fear of any larger fish, while the recognition of a specific predator odour has to be learned.