Sounds of feeding 'work-ups' provide cues for food availability

A feeding 'work-up' is a multi-species aggregation involving dolphins, diving gannets and whales feeding on schooling bait fish. The hypothesis is that sounds produced during a 'workup', which can potentially be heard a significant distance away, provide key cues of food availability. Using drifting hydrophones feeding 'work-ups' were recorded throughout the Hauraki Gulf, New Zealand. Diving gannet 'thumps', fish 'grunts' and bottlenose dolphin 'moans' had peak frequencies of 83 Hz, 460 Hz, 670 Hz respectively. The recorded sounds were within the hearing capabilities of sharks, large pelagic fish, pinnipeds and cetaceans, therefore it is suggested both con and hetero-specific species are able to detect the acoustic cues.