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 G adus morhua is inherited, naive two-spotted gobies Gobiusculus flavescens w ere exposed to visual or chemical cod stimuli, in order to determine whethe r 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 w as presented either visually or by its odour. Equal amounts of food were av ailable in the 2 habitats. When no predator stimuli were presented in eithe r habitat, the gobies distributed themselves equally between them both. Whe n a visual stimulus of a cod was presented in 1 of the habitats, they avoid ed 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 co d physically present in 1 habitat, the gobies still did not respond to the introduction of cod odour the following day, However, after having experien ced 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 h as an innate fear of any larger fish, while the recognition of a specific p redator odour has to be learned.