2005 Strategic Environmental Assessment SEA6 Technical Report - Sea Mammal Research - Background Information on Marine Mammals (Irish Sea)

This report is a contribution to the Strategic Environmental Assessment (SEA6) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Seven marine mammal species are known to occur regularly in the SEA6 area. A relatively small but fairly discrete population of grey seals utilises all but the northwest Irish Sea. Harbour seals are found primarily in the far north of the area. Harbour porpoises are seen year round throughout the area and bottlenose dolphins are present year round off Wales. Minke whales, Risso's dolphins and short-beaked common dolphins are regularly seen in summer mainly in the far south. The report discusses the distribution and abundance of these mammals and their ecological importance. Marine mammals make use of sound for a variety of purposes: finding prey, detecting predators, communication and probably navigation. The offshore oil and gas industry generates underwater noise at every stage of the process: during exploration seismic surveys, drilling, production and decommissioning. The effects of these different sources of underwater noise on marine mammals are discussed. The use of explosives for underwater cutting and demolition during the decommissioning of platforms and installations may pose a serious threat to some marine mammals. The effects of pollution on seals and cetaceans are discussed, including the effects of oil spills. The prevalence of disease among the marine mammal populations is reviewed.本报告系贸易与工业部（现能源与气候变化部）所开展的第六次战略环境评估（Strategic Environmental Assessment，SEA6）的支撑性研究成果。已知该评估区域内定期分布有7种海洋哺乳动物：灰海豹（grey seals）拥有一个规模相对较小但分布相对独立的种群，其活动范围覆盖除爱尔兰海西北部以外的所有区域；港海豹（Harbour seals）主要栖息于该区域的最北端；港湾鼠海豚（Harbour porpoises）全年均可见于整片评估区域，宽吻海豚（bottlenose dolphins）则常年活动于威尔士周边海域。小须鲸（Minke whales）、里氏海豚（Risso's dolphins）与短喙普通海豚（short-beaked common dolphins）主要于夏季定期现身于区域最南部水域。本报告阐述了上述海洋哺乳动物的分布特征、种群数量及其生态重要性。 海洋哺乳动物可借助声音实现多种生存功能：觅食、侦测天敌、个体通讯，或还可用于导航。近海油气产业在作业全流程的各个环节均会产生水下噪声，涵盖勘探地震勘测、钻井、生产以及平台退役阶段。本报告探讨了各类水下噪声源对海洋哺乳动物造成的影响。在平台及相关海洋设施的退役作业中，用于水下切割与爆破的炸药可能对部分海洋哺乳动物构成严重威胁。 本报告还探讨了包括溢油事件在内的各类污染对海豹与鲸豚类动物的影响，并综述了海洋哺乳动物种群的疾病流行情况。