Noise associated with shipping has the potential to cause disturbance to marine animals, including the marine mammals, fish and birds designated under the Habitats Directive. The main source of noise from vessels is generated by the engine, which may travel via the atmosphere or be transmitted through the structure of the craft. The volume of sound generated and transmitted into the air or water will depend on the size, design and location of the engine, and the craft’s size and construction. There have been very few studies carried out to investigate the effects of noise pollution in UK coastal waters, particularly with regard to ship-generated noise on marine animals. The level of information that is available on underwater noise is generally inconclusive with regard to the effects on marine life.

Marine mammals are known to continue to use areas with very high levels of boat traffic and noise, such as Galveston Harbour in Texas (ICES 1991). However, there is concern over noise pollution in general which tends to centre on the possible behavioural effects and that in the worse cases marine mammals, fish or birds may be driven away from their home territories. In recognition that noise and erratic boat movements can distract feeding dolphin or drive them away, codes of conduct have been prepared for vessels operating in Cardigan Bay and the Firth of Forth (Section 3.4.3).

Dolphins have a sensitive echo location system. Concerns have been expressed that underwater noise may disturb dolphins, however, there is little research available to support or disprove these concerns in relation to noise from commercial shipping and recreational craft in UK waters. The preliminary findings of a study undertaken as part of the Durlston Dolphin Research Programme indicates that it is unlikely that bottlenose dolphin are disturbed by the noise generated by high speed ferries operating out of Poole Harbour (case study - Browning, Williams & Haarland 1997).

Observations of seals made as part of the work of the Sea Mammal Research Unit show, not surprisingly, that seals are usually less tolerant to disturbance during the breeding season and when feeding their offspring. Further research is required to establish whether seals exhibit behavioural changes as a result of noise from shipping and port operations. Seals generally choose relatively undisturbed areas to come ashore and breed. Ironically, RAF bombing ranges, which despite being the source of a certain level of noise pollution have been observed to provide suitable areas for colonies of seals. This observation is likely to be a result of the restrictions to public access along these stretches of coast (Sea Mammal Research Unit personal communication 1998).

The effect of underwater noise has been more extensively studied with regard to the impact of seismic surveys on marine animals, and the resultant disturbance to fish feeding behaviour, repulsion from fishing grounds, avoidance behaviour in sea mammals and disturbance of breeding colonies of birds. Effects of the high level, low frequency sounds from seismic surveys are thought to be temporary, with lasting harm to fish, sea birds and mammals unlikely (Turnpenny & Nedwell 1994).

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