Collisions between vessels and marine animals

The movement of ships and boats to and from ports may potentially have some effect on marine life simply by virtue of their presence. This is particularly the case with high-speed leisure craft and in marine SACs designated for their marine mammals. There have been a number of studies on the effects of vessel movement on marine mammals. These include the Institute of Zoology’s Marine Mammal Strandings Project (Jepson personal communication 1998), the Natural History Museum’s stranded whale recording scheme (Muir personal communication 1998), the work of the Sea Mammal Research Unit and Durlston Country Park in Dorset (Browning personal communication 1998) and studies undertaken in Cardigan Bay (Evans personal communication 1998) and the Firth of Forth (Reid personal communication 1998). Research has shown that although a rare occurrence in UK waters, collisions do occur between marine mammals and ships/boats operating at speed, which may result in fatal injuries or wounding. However, quantified information on the occurrence of these incidents is very limited.

Over the past few years, there have been a limited number of incidents where dead and stranded marine mammals, often harbour porpoises, have shown evidence of propeller damage or massive trauma, indicative of ship collisions. In Scottish waters there have been recent reports of fatal collisions between vessels and basking sharks, which are a protected species under the Wildlife and Countryside Act. Further collision incidents are known to taken place with seals, however, there is very little information available on the occurrence of these events (National Seal Sanctuary personal communication 1998). Generally, the risk of collisions with marine mammals is greater for recreational craft and dolphin-watching boats and guidelines have been developed for minimising the disturbance to dolphins and porpoises from these activities.

As one would expect, wherever possible, animals will avoid contact with moving vessels. However this is not always the case, for example dolphins and porpoises often actively seek out moving vessels and swim close alongside in the bow wave which may make them vulnerable to injury from collision (A. Muir Natural History Museum personal communication 1998). Many mariners, including yachtsmen, regularly report the enthusiasm with which dolphins accompany their vessels, often for relatively long periods of time before diving away. For example, bottlenose dolphins in the Moray Firth readily approach vessels, to bow ride or to accompany them through the narrows (UK CEED 1993).

Research has been undertaken by the Sea Mammal Research Unit to establish the distribution of seals around UK waters. Observations show that seals co-exist with shipping in many areas around the coast. The presence of fishing vessels may even provide an additional food source as a result of the practice of discarding unwanted fish overboard. It is unlikely that other marine animals will be affected greatly by vessel movements in the UK.

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