Joint Nature Conservation Committee
UK waters encompass a wide range of seabed topography and physical and chemical conditions that create a huge diversity of marine ecosystems. These in turn influence the availability of biological resources that attract a significant diversity of marine mammals for European waters. In all, 28 cetacean species have been recorded in UK waters, of which eleven species occur regularly. Cetaceans in a given area are usually part of a larger and more widespread biological population. As a consequence of their wide ranges, all cetaceans are protected internationally through various conventions and agreements. Consequently, to be effective, their conservation needs must be considered on an international basis including the monitoring and surveillance essential to meet the requirements of the EU Habitats Directive and the Marine Strategy Framework Directive (MSFD). The smallest and most abundant cetacean in UK (and neighbouring) shelf areas is the harbour porpoise (Phocoena phocoena). The species occurs throughout continental shelf waters and may, therefore, be affected by a range of human activities occurring in the same waters. The most important pressures identified include mortality as bycatch in fishing gear, acoustic disturbance, and bioaccumulation of persistent organic chemicals such as PCBs. Some pressures may lead to mortality, whilst others raise concern about potential long-term impacts on population health. The pressures identified that require further research include habitat degradation, prey depletion (e.g. competition with fisheries for food) and climate change. It should be noted that the cumulative effect of any combination of these pressures may result in more deleterious consequences than any single pressure in isolation. Approaches to conservation need to be multifaceted, adaptable and tailored to particular local or regional conditions as appropriate. A key factor in determining whether our conservation efforts are effective is a better understanding of the abundance and distribution patterns of harbour porpoises, including seasonal variations, as well as better information on basic life history parameters such as reproductive rates and mortality. Such knowledge will help determine the magnitude of impacts experienced by the population and would help determine whether efforts aimed at reducing such pressures are effective. This paper outlines our current understanding of the anthropogenic pressures experienced by harbour porpoise and the mitigation options available to reduce these pressures. The UK currently has a conservation strategy for harbour porpoise, initially published in 2000, which is further supported by the UK Bycatch Response Strategy. Together these take a risk-based approach to harbour porpoise conservation. The strategies will be reviewed and updated where appropriate in light of the finding in this literature review.
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