Hypotheses on the acoustics of whales, dolphins and porpoises in bubbly water

The use made of acoustics for communication and echolocation by cetaceans is well-known. We are also familiar with the ability of gas bubbles in the ocean to complicate and confound human attempts to achieve these tasks for ourselves. Some cetaceans must deal with bubbles as a result of their location (for example as occurs with those species restricted to coastal regions): others actively generate bubbles to aid their feeding. Data is scarce as to what extent, if any, cetaceans have exploited the acoustical effects of bubbles, or undertake tactics to compensate for their deleterious effects. The absence of data provides a fruitful opportunity for hypothesis. Having evolved over tens of millions of years to cope with the underwater acoustic environment, cetaceans may have developed extraordinary techniques from which we could learn. This paper outlines some of the possible interactions, ranging from the exploitation of acoustics by humpback whales (Megaptera novaeangliae) in bubble nets to trap prey, to techniques by which coastal dolphins (e.g. of the genus Cephalorhynchus) could successfully echolocate in bubbly water. These hypotheses are then used to develop practical sonar technology for use in bubbly waters