The effect of boat noise on the behaviour of bluefin tuna Thunnus thynnus was investigated\ud in the Egadi Islands, Sicily, during spring 2005 using a fixed tuna trap set near shipping routes.\ud Tuna behaviour was observed when exposed to both natural ambient sound and sound generated by\ud hydrofoil passenger ferries, small boats and large car ferries. Acoustical and behavioural analyses\ud were conducted with and without extraneous sound to define a list of behavioural categories. Each\ud vessel produced different engine sounds with regard to their composition and bandwidth, and all\ud were distinctly different from ambient sound levels. In the absence of boat noise, tuna assumed a concentrated\ud coordinated school structure with unidirectional swimming and without a precise shape.\ud When a car ferry approached, tuna changed swimming direction and increased their vertical movement\ud toward surface or bottom; the school exhibited an unconcentrated structure and uncoordinated\ud swimming behaviour. Hydrofoils appeared to elicit a similar response, but for shorter periods. Agonistic\ud behaviour was more evident when exposed to sounds from outboard motors of small boats. This\ud study showed that local noise pollution generated by boats produced behavioural deviations in tuna\ud schools. Schooling enhances tuna homing accuracy during their spawning migration, and an alteration\ud in schooling behaviour can affect the accuracy of their migration to spawning and feeding\ud grounds

The study of marine soundscapes is an emerging field of research that contributes important information about biological compositions and environmental conditions. The seasonal and circadian soundscape trends of a marine protected area (MPA) in the Mediterranean Sea have been studied for one year using an autonomous acoustic recorder. Frequencies less than 1 kHz are dominated by noise generated by waves and are louder during the winter; conversely, higher frequencies (4–96 kHz) are dominated by snapping shrimp, which increase their acoustic activity at night during the summer. Fish choruses, below 2 kHz, characterize the soundscape at sunset during the summer. Because there are 13 vessel passages per hour on average, causing acoustic interference with fish choruses 46% of the time, this MPA cannot be considered to be protected from noise. On the basis of the high seasonal variability of the soundscape components, this study proposes a one-year acoustic monitoring protocol using the soundscape methodology approach and discusses the concept of MPA size.

Within the set of risk factors that compromise the conservation of marine biodiversity, one of the least understood concerns is the noise produced by human operations at sea and from land. Many aspects of how noise and other forms of energy may impact the natural balance of the oceans are still unstudied. Substantial attention has been devoted in the last decades to determine the sensitivity to noise of marine mammals—especially cetaceans and pinnipeds—and fish because they are known to possess hearing organs. Recent studies have revealed that a wide diversity of invertebrates are also sensitive to sounds, especially via sensory organs whose original function is to allow maintaining equilibrium in the water column and to sense gravity. Marine invertebrates not only represent the largest proportion of marine biomass and are indicators of ocean health but many species also have important socio-economic values. This review presents the current scientific knowledge on invertebrate bioacoustics (sound production, reception, sensitivity), as well as on how marine invertebrates are affected by anthropogenic noises. It also critically revisits the literature to identify gaps that will frame future research investigating the tolerance to noise of marine ecosystems.