| Harbour porpoise- SW |
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1Action for biodiversity |
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Evidence exists for dramatic declines in porpoise populations since the 1940s, especially in the southern North Sea and the English Channel. This is mirrored by similar declines in the rest of Europe The 1994 Small Cetacean Abundance in the North Sea (SCANS) survey of the North Sea, Channel and Celtic Sea, indicated that the population of harbour porpoise in these waters was approximately 350,000. Two offshore populations of harbour porpoise are of direct relevance in a South West context, those of the Celtic Sea, to the north and west of the region, and the English Channel, to the south and east. The SCANS survey suggests that the Celtic Sea supports in the order of 36,000 individuals in the summer. With current models suggesting a potential growth rate of 4-5%, and an estimated 6% by catch in the offshore hake fishery alone, it would seem that this population is likely to decline in coming years. While more work on modelling is required if population trends are to be monitored accurately, it is clear that Celtic Sea populations are likely to decline if the current rate of bycatch continues. Indeed the Scientific Committee of the International Whaling Committee (Small Cetaceans Sub-Committee) considers that nay bycatch over 1% represents a 'reasonable threshold for concern about the sustainability of catches'. Inshore sightings reflect these offshore distributions. Porpoises can be seen on most days from along the north coast of Devon between Woolacombe Bay and Ilfracombe. Sightings off the south coast are much rarer, although harbour porpoise are occasional recorded in Lyme Bay. Whether these inshore groups should be considered as part of the offshore population is currently unclear. Studies of dolphin and killer whale populations in the US suggest that inshore and offshore groups are genetically distinct, and therefore there is little if any cross over between them. The picture is further complicated by studies which show that inshore porpoises can move a long way offshore. Again there would be major implications for harbour porpoise conservation if these findings were repeated in UK populations. The harbour porpoise is listed in the UK Biodiversity Steering Group Report as a priority species of conservation concern and is listed on Appendix II of CITES, Appendix II of Berne Convention and AnnexesII and IV of the EC Habitats Directive It is also on Appendix 2 of the Bonn Convention and is covered by the terms of the Agreement on Conservation of Small Cetaceans of the Baltic and North Seas (ASCOBANS), a regional agreement under the Bonn Convention. It is protected under Schedule 5 of the Wildlife & Countryside Act 1981. Regional distribution in the South West1
Priority
Areas and natural areas in the South West1
Basic Management requirements1 Relevant ecologyPorpoises from UK waters feed mainly on fish. They specialise in tidal races and along the seabed. However, a wide range of prey is utilised, including shoaling pelagic species such as sand eels and herring. Porpoises can live up to 18 years, although the usual life span is in the order of 11 years. Females mature sexually at around 4 years, after which pregnancies can occur annually. Mating takes place around October with births, usually of single calves, occurring from March to August Current Factors
affecting the species1
South West biodiversity objectives and proposed targets 1 OBJECTIVE 1 Maintain range and numbers of current inshore populations of harbour porpoise within the region. TARGET: ongoing OBJECTIVE 2 Reverse the trend in declining harbour porpoise
numbers within the region
Ensure a sound understanding of the ecology and behaviour of the
harbour porpoise OBJECTIVE 4 Increase awareness of the harbour porpoise, and its importance, amongst the general and seagoing public TARGET: ongoing
National: A UK Biodiversity Action Plan has recently been prepared; Small Cetacean Abundance in the North Sea (SCANS) survey has been undertaken; BYCARE; an international project with EU LIFE funding looked at population modelling; Loughborough University research University research into increasing acoustical reflectivity of fishing nets and 'super pingers'; MAFF run a North Sea Observer scheme and DoE a stranding Regional: Cornwall Wildlife Trust (CWT) run an observer scheme; as well as a restrospective survey, gathering anecdotal evidence for past populations around the South West coast; and an automatic porpoise detector project, to develop equipment for gathering information about porpoise behaviour and numbers.
Proposed Action 1 Policy and legislation
Set and enforce water quality objectives for coastal waters (by
2000) LEAD: EA Management
Investigate means to manage inshore activities, including
fisheries, so as to minimise any adverse effects on harbour porpoise
populations identified by research and monitoring (see below) (by 2010) LEAD: DOE Research and monitoring
Encourage, by funding or other means, research into: b) current factors affecting inshore populations (by 2000) d) harbour porpoise populations prior to decline (by 2002) f) ecology and behaviour of harbour porpoise (by 2010) LEAD: JNCC LEAD: JNCC
Education and awareness raising
Produce and distribute relevant interpretative material (by
1999)
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