Conservation plan for the Harbour Porpoise Phocoena phocoena in The Netherlands: towards a favourable conservation status Kees (C.J.) Camphuysen & Marije L. Siemensma NIOZ Royal Netherlands Institute for Sea Research omslag 2011-7.indd 1 25/08/2011 12:05 Authors C.J. (Kees) Camphuysen Royal Netherlands Institute for Sea Research P.O. Box 59, 1790 AB Den Burg, Texel, NL Tel. + 31 222 369488, E-mail: [email protected] M.L. (Marije) Siemensma Marine Science & Communication Bosstraat 123, 3971 XC Driebergen-Rijssenburg, NL Tel. + 31 6 16830430 E-mail: [email protected] Commissioning This project was commissioned and nanced by the Dutch Ministry of Economics, Agriculture and Innovation Cover illustration Reproduced with permission from The J. Paul Getty Museum, Los Angeles. Jan van de Cappelle (1649) “Shipping in a Calm at Flushing with a States General Yacht Firing a Salute” Oil on oak panel, Unframed: 69.5 x 92.1 cm. The im- age shows numerous animals in the water that could be recognised as Harbour Porpoises, which were abundant at the time. Recommended citation Camphuysen C.J. & M.L. Siemensma (2011). Conservation plan for the Harbour Porpoise Phocoena phocoena in The Netherlands: towards a favourable conservation status. NIOZ Report 2011-07, Royal Netherlands Institute for Sea Re- search, Texel. © 2011 Royal Netherlands Institute for Sea Research omslag 2011-7.indd 4 25/08/2011 12:06 Conservation plan for the Harbour Porpoise Phocoena phocoena in The Netherlands: towards a favourable conservation status Kees (C.J.) Camphuysen & Marije L. Siemensma © 2011 Royal Netherlands Institute for Sea Research 1 Conservation plan Harbour Porpoise in The Netherlands – NIOZ Report 2011-07 Authors C.J. (Kees) Camphuysen Royal Netherlands Institute for Sea Research P.O. Box 59, 1790 AB Den Burg, Texel, NL Tel. + 31 222 369488, E-mail: [email protected] M.L. (Marije) Siemensma Marine Science & Communication Bosstraat 123, 3971 XC Driebergen-Rijssenburg, NL Tel. + 31 6 16830430 E-mail: [email protected] Commissioning This project was commissioned and financed by the Dutch Ministry of Economics, Agriculture and Innovation Cover illustration Reproduced with permission from The J. Paul Getty Museum, Los Angeles. Jan van de Cappelle (1649) “Shipping in a Calm at Flushing with a States General Yacht Firing a Salute” Oil on oak panel, Unframed: 69.5 x 92.1 cm. The image shows numerous animals in the water that could be recognised as Harbour Porpoises, which were abundant at the time. Recommended citation Camphuysen C.J. & M.L. Siemensma (2011). Conservation plan for the Harbour Porpoise Phocoena phocoena in The Netherlands: towards a favourable conservation status. NIOZ Report 2011-07, Royal Netherlands Institute for Sea Research, Texel. © 2011 Royal Netherlands Institute for Sea Research 2 Conservation plan Harbour Porpoise in The Netherlands – NIOZ Report 2011-07 Contents 1. Summary 1. Short summary 2. Korte Nederlandse samenvatting 3. Full summary 2. Preface 3. Introduction 4. Current knowledge 1. Characteristics, size, reproduction and longevity 2. Position in the marine food web, foraging ecology, predators, diet, competitors 3. World status (international context) 4. Historical population status in The Netherlands 5. Current population status in the Southern Bight/The Netherlands 6. Strandings, cause of death, age composition and sex ratio 7. Reproductive activity in Dutch waters 8. Migratory movements, resident stocks 9. Evidence for sea areas of particular importance 10. Conservation status 11. Discussion and conclusions 5. Observed threats (factors causing loss or decline) 1. Incidental capture (bycatch) 2. Siting, land reclamation 3. Vessel strikes 4. Windfarms 5. Acoustic disturbance; loud explosive sounds 6. Mining activities 7. Marine litter 8. Marine pollution 9. Reduced prey availability 10. Natural predators, competition 11. Infectious disease 12. Parasites 13. Morbillivirus 14. Potential biological removal (human caused mortality) 15. Discussion and conclusions 6. Overview of existing mitigation measures 1. Incidental capture (bycatch) 2. Siting, land reclamation 3. Vessel strikes 4. Windfarms 5. Acoustic disturbance; loud explosive sounds 6. Mining activities 7. Marine litter 8. Marine pollution 3 Conservation plan Harbour Porpoise in The Netherlands – NIOZ Report 2011-07 9. Reduced prey availability 10. Natural predators, competition 11. Infectious disease 12. Parasites 13. Morbillivirus 7. Policy and legislative context 1. Introduction 2. Geographical scope 3. International legislation 4. European legislation 5. European fisheries regulations 6. National legislation 7. National fisheries regulations 8. Discussion and conclusions 8. Stakeholder consultation 9. Concrete measures: research proposals and mitigation measures 1. Scientific research a. Population status b. Acoustic monitoring c. Strandings d. Necropsies, assessment of the cause of death e. Fisheries responsible for bycatch f. Field studies of age composition g. Resources and habitat requirements h. Behaviour studies in captivity i. Reporting results, quality control j. Main action points (scientific research) 2. Policy measures and mitigation a. General recommendations b. Policy measures mitigating incidental capture (bycatch) c. Policy measures acoustic disturbance; loud explosive sounds d. Main action points (mitigation measures) 10. Discussion and conclusions 11. Acknowledgements 12. References 4 Conservation plan Harbour Porpoise in The Netherlands – NIOZ Report 2011-07 1. Summary 1.1 Short summary This is a conservation plan for the Harbour Porpoise Phocoena phocoena based on the current seasonal occurrence and abundance of porpoises within waters under Dutch jurisdiction. The conservation status of the Harbour Porpoise in The Netherlands has recently been evaluated as ‘Inadequate’, and the population as ‘Vulnerable’. From 1900 to the early 1950s, Harbour Porpoises were abundant and widespread in coastal waters throughout the southern North Sea, including Dutch waters. The animal declined and was considered locally extinct during the 1960s-1980s. Harbour Porpoises have increased markedly in numbers in the southern North Sea in recent decades. Given changes in distribution and abundance, the conservation status of porpoises in Dutch waters is likely to require an update in the near-future. Harbour Porpoises are most abundant in relatively shallow sea areas and often forage near or at the sea bottom. Their prey spectrum includes pelagic and demersal prey species: different species of fish, cephalopods, crustaceans and polychaetes. The global abundance of the Harbour Porpoise is at least about 700,000 individuals. Within the North Sea at large, in 2005, total abundance was estimated at 230,000 individuals. A marked change in distribution was found, with considerably larger numbers of porpoises in the southern half of the North Sea in the 2005 than during an earlier census in 1994. Aerial surveys covering 50% of the Dutch sector of the North Sea produced 37,000 Harbour Porpoises in Feb-April 2009 and 56,000 in Mar 2010. The current Harbour Porpoise conservation plan is a generic plan rather than area-orientated: recent research in Dutch waters failed to identify areas or regions of particular ecological significance for Harbour Porpoises for any significant length of time. Incidental capture in fishing gear (bycatch) is considered to be the most significant threat to Harbour Porpoise populations worldwide. In The Netherlands, some 150-250 animals washing ashore per annum are at least bycatch-suspect. The main type of fishing gear responsible for drowning is currently unknown, but set-nets (passive gear) are the main suspects. Bycatches occurred year-round and throughout the study area. The catch composition during which most porpoise strandings occurred varied and no set-net fisheries should be excluded a priori from an observer scheme. An onboard observer scheme should be established with priority in the winter fisheries, Dec-Mar, in the northern coastal zone (IJmuiden- Vlieland). While there is concrete evidence for avoidance behaviour of loud (explosive) underwater sounds (such as pile driving for windfarm construction, seismic exploration, underwater explosions, and naval sonar operation), there is no factual evidence for lethal damage. Adequate studies of hearing damage and death as a result of underwater sound are lacking. The distributional shift of Harbour Porpoises from more northerly parts of the North Sea into the Southern Bight may have been caused by a reduction in available prey in the north. Studies of the ecology of Harbour Porpoises in the southern North Sea are required to shed more light on prey availability and resources (stocks). Siting, vessel strikes, the operational phase of windfarms, offshore mining, marine litter, chemical pollution, (chronic) marine oil pollution, natural predators, infectious disease, and parasites are all issues of concern that may in part require additional study, none of which required local (or regional, i.e. on a southern North Sea scale) mitigation measures, but rather on a higher governance level. 5 Conservation plan Harbour Porpoise in The Netherlands – NIOZ Report 2011-07 None of the demonstrated threats can be quantified satisfactory, given the slender factual data currently at hand. It is obvious that further research is required, before effective mitigation measures can be proposed and the precautionary approach (UNESCO 2005) could be the safest way forward. The Harbour