Setting Maximum Mortality Limits for Harbour Porpoises in Dutch Waters to Achieve Conservation Objectives


Harbour porpoises in the North Sea are protected under national and EU legislation, and under the regional agreement ASCOBANS, within the UN Convention on Migratory Species. As yet, no methods exist to quantify the cumulative impacts of direct anthropogenic mortality (e.g. by-catch) and indirect effects of human activities (e.g. contaminants) on porpoise populations. However, procedures do exist for assessing whether total anthropogenic mortality may result in failure to meet conservation objectives. While the ultimate aim is to reduce the number of such deaths to zero, ASCOBANS has an interim objective to reduce anthropogenic mortality to a level that will allow recovery of populations. Several different criteria have been proposed as limits to anthropogenic mortality that may still allow conservation objectives to be met. These criteria include simple percentages of the best population abundance estimate and more complex procedures that account for uncertainty and other information about the population. In this paper, we report new estimates of abundance for porpoises in Dutch waters, and we apply several methods to calculate maximum anthropogenic mortality limits from these estimates. We considered whether these mortality limits would meet the objective of the ASCOBANS agreement and other international obligations, and how these limits may be applied at a national level rather than the biological population level. The current simple approach of a limit of 1.7% of the best abundance estimate may not satisfy conservation objectives. We recommend the use of management procedures for setting mortality limits that take into account available data including associated uncertainties and biases, and whose performance has been extensively tested through simulation.

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M. Scheidat, R. Leaper, M. Heuvel-Greve and A. Winship, "Setting Maximum Mortality Limits for Harbour Porpoises in Dutch Waters to Achieve Conservation Objectives," Open Journal of Marine Science, Vol. 3 No. 3, 2013, pp. 133-139. doi: 10.4236/ojms.2013.33014.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] P. J. H. Reijnders, “Harbour Porpoises Phocoenaphocoena in the North Sea: Numerical Responses to Changes in Environmental Conditions,” Aquatic Ecology, Vol. 26, 1992, pp. 1386-2588.
[2] C. J. Camphuysen and M. L. Siemensma, “Conservation Plan for the Harbour Porpoise Phocoenaphocoena in The Netherlands: Towards a Favourable Conservation Status,” NIOZ Report 2011-07, Royal Netherlands Institute for Sea Research, Texel, 2011.
[3] ASCOBANS, “ASCOBANS Conservation Plan for Harbour Porpoises (Phocoena phocoena L.) in the North Sea,” 6th Meeting of the Parties to ASCOBANS, Bonn, Germany, 16-18 September 2009, 35 pp.
[4] ASCOBANS, “MOP 3: Resolution on Incidental Take of Small Cetaceans,” ASCOBANS, Bristol, 2000.
[5] ASCOBANS, “MOP 2: Resolution on Incidental Take of Small Cetaceans,” ASCOBANS, Bonn, 1997.
[6] P. R. Wade, “Calculating Limits to Human-Caused Mortality of Cetaceans and Pinnipeds,” Marine Mammal Science, Vol. 14, No. 1, 1998, pp. 1-37. doi:10.1111/j.1748-7692.1998.tb00688.x
[7] A. E. Punt and G. P. Donovan, “Developing Management Procedures That Are Robust to Uncertainty: Lessons from the International Whaling Commission,” ICES Journal of Marine Science, Vol. 64, No. 4, 2007, pp. 603-612. doi:10.1093/icesjms/fsm035
[8] J. G. Cooke, “Improvement of Fishery-Management Advice through Simulation Testing of Harvest Algorithms,” ICES Journal of Marine Science, Vol. 56, No. 6, 1999, pp. 797-810. doi:10.1006/jmsc.1999.0552
[9] J. Cooke, R. Leaper, P. Wade, D. Lavigne and B. Taylor, “Management Rules for Marine Mammal Populations: A Response to Lonergan,” Marine Policy, Vol. 36, No. 2, 2012, pp. 389-392. doi:10.1016/j.marpol.2011.06.009
[10] P. Berggren, P. R. Wade, J. Carlstrom and A. J. Read, “Potential Limits to Anthropogenic Mortality for Harbour Porpoises in the Baltic Region,” Biological Conservation, Vol. 103, 2002, pp. 313-322. doi:10.1016/S0006-3207(01)00142-2
[11] R. Williams, A. Hall and A. Winship, “Potential Limits to Anthropogenic Mortality of Small Cetaceans in Coastal Waters of British Columbia,” Canadian Journal of Fisheries and Aquatic Sciences, Vol. 65, 2008, pp. 1867-1878. doi:10.1139/F08-098
[12] A. J. Winship, “Estimating the Impact of Bycatch and Calculating Bycatch Limits to Achieve Conservation Objectives as Applied to Harbour Porpoise in the North Sea,” PhD Thesis, University of St Andrews, St Andrews, 2009.
[13] C. Smeenk, “The Harbour Porpoise Phocoenaphocoena (L., 1758) in The Netherlands: Stranding Records and Decline. Lutra, Vol. 30, 1987, pp. 77-90.
[14] C. J. Camphuysen, “The Harbour Porpoise Phocoenaphocoena in the Southern North Sea. II: A Come-Back in Dutch Coastal Waters?” Lutra, Vol. 37, No. 1, 1994, pp. 54-61.
[15] C. J. Camphuysen, “Recent Trends and Spatial Patterns in Nearshore Sightings of Harbour Porpoises (Phocoena- phocoena) in The Netherlands (Southern Bight, North Sea), 1990-2010,” Lutra, Vol. 54, No. 1, 2011, pp. 37-44.
[16] P. J. H. Reijnders, M. F. Leopold, C. J. Camphuysen, H. J. L. Heessen and R. A. Kastelein, “The Status of the Harbour Porpoise, Phocoenaphocoena, in Dutch Waters and the State of Related Research in the Netherlands: An Overview,” Forty-Sixth Report of the International Whaling Commission, 1996, pp. 607-611
[17] SCANS-II, “Small Cetaceans in the European Atlantic and North Sea SMRU,” Scottish Oceans Institute, University of St Andrews, 2008.
[18] C. J. Camphuysen, “The Return of the Harbour Porpoise (Phocoenaphocoena) in Dutch Coastal Waters,” Lutra, Vol. 47, No. 2, 2004, pp. 113-122.
[19] M. Scheidat, H. Verdaat and G. Aarts, “Using Aerial Surveys to Estimate Density and Distribution of Harbour Porpoises in Dutch Waters,” Journal of Sea Research, Vol. 69, 2012, pp. 1-7. doi:10.1016/j.seares.2011.12.004
[20] S. C. V. Geelhoed, M. Scheidat, R. S. A. van Bemmelen and G. Aarts, Abundance of harbour porpoises Phocoenaphocoena on the Dutch Continental Shelf, Aerial Surveys in July 2010-March 2011,” Lutra, Vol. 56, No. 1, 2013, pp. 45-57.
[21] P. G. H. Evans and J. Teilmann, “Report of ASCOBANS /HELCOM Small Cetacean Population Structure Workshop,” Bonn, 8-10 October 2007.
[22] B. Taylor, “‘Best’ Abundance Estimates and Best Management: Why They Are Not the Same,” US Department of Commerce, NOAA Technical Memorandum NMFSSWFSC-188, 1993, 20 pages.
[23] A. Grone, L. Begeman and S. Hiemstra, “Postmortaal Onderzoek van Bruinvissen in Nederlandse Wateren 2009-2011. Report for the Ministerie van Economische Zaken, Landbouw & Innovatie,” Verplichting nummer: 140000 353; Relatie nummer 101710, 2011.
[24] M. Scheidat and M. Van den Heuvel Greve, “Annual National Report The Netherlands,” 19th ASCOBANS Advisory Committee Meeting, Galway, 20-22 March 2012.
[25] J. E. Moore, “Management Reference Points to Account for Direct and Indirect Impacts of Fishing on Marine Mammals,” Marine Mammal Science, 2012, in Press. doi:10.1111/j.1748-7692.2012.00586.x
[26] P. D. Jepson, P. M. Bennett, R. Deaville, C. R. Allchin, J. R. Baker and R. J. Law, “Relationships between Polychlorinated Biphenyls and Health Status in Harbor Porpoises (Phocoenaphocoena) Stranded in the United Kingdom,” Environmental Toxicology and Chemistry, Vol. 24, No. 1, 2005, pp. 238-248. doi:10.1897/03-663.1
[27] G. J. Pierce, M. B. Santos, S. Murphy, J. A. Learmonth, A. F. Zuur, E. Rogan, P. Bustamante, F. Caurant, V. Lahaye, V. Ridoux, B. N. Zegers, A. Mets, M. Addink, C. Smeenk, T. Jauniaux, R. J. Law, W. Dabin, A. López, J. M. Alonso Farré, A. F. González, A. Guerra, M. García-Hartmann, R. J. Reid, C. F. Moffat, C. Lockyer and J. P. Boon, “Bioaccumulation of Persistent Organic Pollutants in Female Common Dolphins (Delphinusdelphis) and Harbour Porpoises (Phocoenaphocoena) from Western European Seas: Geographical Trends, Causal Factors and Effects on Reproduction and Mortality,” Environmental Pollution, Vol. 153, No. 2, 2008, pp. 401-415. doi:10.1016/j.envpol.2007.08.019

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