Sound production during competitive feeding in the grey gurnard

The acoustic repertoire of captive grey gurnard Eutrigla gurnardus during competitive feeding consisted of three types of sound: knocks, grunts and growls. Knocks were audible as a single sound, whereas grunts and growls were perceived as longer, pulsed sounds to the human ear. Typically, knocks were composed of 1–2 pulses, grunts of 4–8 pulses and growls >10 pulses. Growls were longer and had shorter pulse periods than grunts. All sound types had peak frequencies of c . 500 Hz. The sequences of behaviours observed during feeding interactions suggest that grey gurnard obtain food both by scramble and contest tactics. Competing fish emitted knocks mainly while grasping a food item and also during other non‐agonistic behaviour, suggesting that knock production may reflect a state of feeding arousal but could also serve as a warning of the forager's presence to nearby competitors. Grunts were mainly emitted during frontal displays, which were the most frequent behavioural act preceding grasps, suggesting that they may play a role in deterring other fish from gaining access to disputed food items.