Marine petroleum exploration involves the repetitive use of high-energy noise sources, air-guns, that produce a short, sharp, low-frequency sound. Despite reports of behavioral responses of fishes and marine mammals to such noise, it is not known whether exposure to air-guns has the potential to damage the ears of aquatic vertebrates. It is shown here that the ears of fish exposed to an operating air-gun sustained extensive damage to their sensory epithelia that was apparent as ablated hair cells. The damage was regionally severe, with no evidence of repair or replacement of damaged sensory cells up to 58 days after air-gun exposure.

An experimental program was run by the Centre for Marine Science and Technology of Curtin University between March 1996 and October 1999 to study the environmental implications of offshore seismic survey noise. This work was initiated and sponsored by the Australian Petroleum Production and Exploration Association. The program:characterised air gun signal measurements; modelled air gun array sources and horizontal air gun signal propagation;developed an 'exposure model' to predict the scale of potential biological effects for a given seismic survey over its duration;made observations of humpback whales traversing a 3D seismic survey;carried out experiments of approaching humpback whales with a single operating air gun;carried out trials with an air gun approaching a cage containing sea turtles, fishes or squid; andmodelled the response of fish hearing systems to airgun signals.The generalised response of migrating humpback whales to a 3D seismic vessel was to take some avoidance manoeuvre at >4 km then to allow the seismic vessel to pass no closer than 3 km. Humpback pods containing cows which were involved in resting behaviour in key habitat types, as opposed to migrating animals, were more sensitive and showed an avoidance response estimated at 7−12 km from a large seismic source. Male humpbacks were attracted to a single operating air gun due to what was believed the similarity of an air gun signal and a whale breaching event (leaping clear of the water and slamming back in). Based on the response of captive animals to an approaching single air gun and scaling these results, indicated sea turtles displayed a general 'alarm' response at an estimated 2 km range from an operating seismic vessel and behaviour indicative of avoidance estimated at 1 km. Similar trials with captive fishes showed a generic fish 'alarm' response of swimming faster, swimming to the bottom, tightening school structure, or all three, at an estimated 2−5 km from a seismic source. Modelling the fish ear predicted that at ranges

Anthropogenic sound in the marine environment continues to increase. Sound sources range from increased vessel traffic to transient but intense sounds such as those produced by seismic air guns, pile driving, or some sonars. While most interest in anthropogenic sounds has focused on marine mammals, there is an increasing concern regarding the impact of such sounds on fishes and marine invertebrates. Since the inner ear hearing receptors of fishes are similar to those of marine mammals, any effects seen on the hearing receptors of marine mammals may also be found in fishes and vice versa. Despite increasing interest in the effects of sounds on fishes, this issue has only been addressed on the most limited scale. Here we review the current literature in this area. It has been reported that high sound levels can damage the inner ear sensory cells, produce hearing loss (threshold shifts), elicit stress responses, and alter the behavior of fishes. At least in terms of hearing loss, these effects are modulated by exposure sound level and duration. The effects of various types of sound (e.g., impulsive vs. continuous) and long-term impacts of how anthropogenic sounds affect the behavior and ecology of fishes need exploration in the future.

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Evaluation of Sargassum sp. as a nutrient-sink in an integrated seaweed-prawn (ISP) culture system,

It is widely suspected that anthropogenic sound could impact the life and survival of marine mammals. One of the major sources of anthropogenic sounds in many parts of the world are seismic air guns used in geologic exploration. Yet there are few data on the physiological and behavioral impacts of air-guns on fishes or marine mammals. This study tested the effects of exposure to air guns on the ears of marine fishes. Pink snapper (Chrysophrys auratus) held in cages were exposed to signals from an air gun towed toward and away from the cages, mimicking the stimulus from an approaching/passing seismic vessel. Results from scanning electron microscopic examination of the ears showed extensive damage occurring weeks after exposure. Damage included deep holes in the saccular epithelium in places where sensory hair cells would be located, and/or ‘‘blebbing’’ on the surface of the epithelium suggesting dying sensory cells. While it is recognized that fishes outside of a cage might swim away from a loud sound, the results reported here suggest that very intense sounds could have a significant impact on the auditory system of fishes, and perhaps other marine organisms.

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