[en] Ecological indicators for monitoring strategies are expected to combine three major characteristics: ecological significance, statistical credibility, and cost-effectiveness. Strategies based on stranding networks rank highly in cost-effectiveness, but their ecological significance and statistical credibility are disputed. Our present goal is to improve the value of stranding data as population indicator as part of monitoring strategies by constructing the spatial and temporal null hypothesis for strandings. The null hypothesis is defined as: small cetacean distribution and mortality are uniform in space and constant in time. We used a drift model to map stranding probabilities and predict stranding patterns of cetacean carcasses under H0 across the North Sea, the Channel and the Bay of Biscay, for the period 1990-2009. As the most common cetacean occurring in this area, we chose the harbour porpoise Phocoena phocoena for our modelling. The difference between these strandings expected under H0 and observed strandings is defined as the stranding anomaly. It constituted the stranding data series corrected for drift conditions. Seasonal decomposition of stranding anomaly suggested that drift conditions did not explain observed seasonal variations of porpoise strandings. Long-term stranding anomalies increased first in the southern North Sea, the Channel and Bay of Biscay coasts, and finally the eastern North Sea. The hypothesis of changes in porpoise distribution was consistent with local visual surveys, mostly SCANS surveys (1994 and 2005). This new indicator could be applied to cetacean populations across the world and more widely to marine megafauna.
Asseburg C, Harwood J, Matthiopoulos J, Smout S (2006) The functional response of generalist predators and its implications for the monitoring of marine ecosystems. In: Camphusen CJ, Boyd IL, Wanless S, editors. Top Predators in Marine Ecosystems: Their Role in Monitoring and Management (Conservation Biology). New York: Cambridge University Press. 262-274.
Sergio F, Newton I, Marchesi L, Pedrini P, (2006) Ecologically justified charisma: preservation of top predators delivers biodiversity conservation. Journal of Applied Ecology 43: 1049-1055.
Sergio F, Caro T, Brown D, Clucas B, Hunter J, et al. (2008) Top predators as conservation tools: ecological rationale, assumptions, and efficacy. Annu Rev Ecol Evol Syst 39: 1-19.
Mace GM, Baillie JEM, (2007) The 2010 Biodiversity Indicators: Challenges for Science and Policy. Conservation Biology 21: 1406-1413.
Boyd IL, Wanless S, Camphuysen J (2006) Introduction. In: Camphusen CJ, Boyd IL, Wanless S, editors. Top Predators in Marine Ecosystems: Their Role in Monitoring and Management (Conservation Biology). New York: Cambridge University Press. 1-11.
Iverson SJ, Stirling I, Lang SL (2006) Spatial and temporal variation in the diets of polar bears across the Canadian Arctic: indicators of changes in prey populations and environment. In: Camphusen CJ, Boyd IL, Wanless S, editors. Top Predators in Marine Ecosystems: Their Role in Monitoring and Management (Conservation Biology). New York: Cambridge University Press. 98-118.
Heithaus MR, Frid A, Wirsing AJ, Worm B, (2008) Predicting ecological consequences of marine top predator declines. Trends in Ecology and Evolution 23: 202-210.
Wallach AD, Murray BR, O'Neil AJ, (2009) Can threatened species survive where the top predator is absent? Biol Conserv 142: 43-52.
Elzinga CL, Salzer DW, Willoughby JW, Gibbs JP (2001) Monitoring plant and animal populations. Hoboken, NJ: Blackwell Science. 360 p.
Hinds WT, (1984) Towards monitoring of long-term trends in terrestrial ecosystems. Environmental Conservation 11: 11-18.
Schiller A, Hunsaker CT, Kane MA, Wolfe AK, Dale VH, et al. (2001) Communicating ecological indicators to decision makers and the public. Conservation Ecology 5: 19.
Müller F, Lenz R, (2006) Ecological indicators: Theoretical fundamentals of consistent applications in environmental management. Ecological Indicators 6: 1-5.
Turnhout E, Hisschemöller M, Eijsackers H, (2007) Ecological indicators: between the two fires of science and policy. Ecological Indicators 7: 215-228.
Geraci JR, Lounsbury VJ (2005) Marine mammals ashore: a field guide for strandings. Baltimore, MD: National Aquarium in Baltimore, Inc. 372 p.
Bibby CJ, Lloyd CS, (1977) Experiments to determine the fate of dead birds at sea. Biol Conserv 12: 295-309.
Hlady DA, Burger AE, (1993) Drift-Block Experiments to Analyse the Mortality of Oiled Seabirds off Vancouver Island, British Columbia. Mar Pollut Bull 26: 495-501.
Degange AR, Doroff AM, Monson DH, (1994) Experimental recovery of sea otter carcasses at Kodiak Island, Alaska, following the Exxon Valdez oil spill. Marine mammal science 10: 492-496.
Garshelis DL, (1997) Sea Otter Mortality Estimated from Carcasses Collected after the Exxon Valdez Oil Spill. Conservation Biology 11: 905-916.
Epperly SP, Braun J, Chester AJ, Cross FA, Merriner JV, et al. (1996) Beach Strandings as an indicator of at-sea mortality of sea turtles. Bulletin of Marine Science 59: 289-297.
Hart KM, Mooreside P, Crowder LB, (2006) Interpreting the spatio-temporal patterns of sea turtle strandings: Going with the flow. Biol Conserv 129: 283-290.
Koch V, Peckham H, Mancini A, Eguchi T, (2013) Estimating At-Sea Mortality of Marine Turtles from Stranding Frequencies and Drifter Experiments. PLoS ONE 8: e56776 doi:10.1371/journal.pone.0056776.
Pyenson ND, (2010) Carcasses on the coastline: measuring the ecological fidelity of the cetacean stranding record in the eastern North Pacific Ocean. Paleobiology 36: 453-480.
Pyenson ND, (2011) The high fidelity of the cetacean stranding record: insights into measuring diversity by integrating taphonomy and macroecology. Proceedings of the Royal Society B 278(1724): 3608-3616.
Williams R, Gero S, Bejder L, Calambokidis J, Kraus SD, et al. (2011) Underestimating the damage: interpreting cetacean carcass recoveries in the context of the Deepwater Horizon/BP incident. Conservation Letters 4: 228-233.
Peltier H, Dabin W, Daniel P, Van Canneyt O, Dorémus G, et al. (2012) The significance of stranding data as indicators of cetacean populations at sea: Modelling the drift of cetacean carcasses. Ecological Indicators 18: 278-290.
Kirkwood JK, Bennet PM, Jepson PD, Kuiken T, Simpson VR, et al. (1997) Entanglement in fishing gear and other causes of death in cetaceans stranded on the coasts of England and Wales. Vet Rec 141: 94-98.
Jepson PD, Bennet PM, Allchin CR, Law RJ, Kuiken T, et al. (1999) Investigating potential associations between chronic exposure to polychlorinated biphenyls and infectious disease mortality in harbour porpoises from England and Wales. Science of the Total Environment 243/244: 339-348.
Siebert U, Wünschmann A, Weiss R, Franck H, Benke H, et al. (2001) Post-mortem Findings in Harbour Porpoises (Phocoena phocoena) from the German North and Baltic Seas. J Comp Path 124: 102-114.
Siebert U, Gilles A, Lucke K, Ludwig M, Benke H, et al. (2006) A decade of harbour porpoise occurence in German waters- Analyses of aerial surveys, incidental sightings and strandings. Journal of Sea Research 56: 65-80.
Jauniaux T, Petitjean D, Brenez C, Borrens M, Brosens L, et al. (2002) Post-mortem Findings and Causes of Death of Harbour Porpoises (Phocoena phocoena) Stranded from 1990 to 2000 along the Coastlines of Belgium and Northern France. J Comp Path 126: 243-253.
Spitz J, Rousseau Y, Ridoux V, (2006) Diet overlap between harbour porpoise and bottlenose dolphin: An argument in favour of interference competition for food? Estuarine Coastal and Shelf Science 70: 259-270.
Evans PGH, Hammond PS, (2004) Monitoring cetaceans in European waters. Mammal review 34: 131-156.
Hoyt E (2005) Marine Protected Areas for Whales, Dolphins and Porpoises. London: Earthscan. 491 p.
Jefferson TA, Curry BE, (1994) A global review of porpoise (Cetacea: Phocoenidae) mortality in gillnets. Biol Conserv 67: 167-183.
Tregenza NJC, Berrow SD, Hammond PS, Leaper R, (1997) Harbour porpoise (Phocoena phocoena L.) by-catch in set gillnets in the Celtic Sea. ICES Journal of Marine Science: Journal du Conseil 54: 896-904.
Vinther M, (1999) Bycatches of harbour porpoises (Phocoena phocoena L.) in Danish set-net fisheries. J Cetacean Res Manage 1: 123-135.
Leeney RH, Amies R, Broderick AC, Witt MJ, Loveridge J, et al. (2008) Spatio-temporal analysis of cetacean strandings and bycatch in a UK fisheries hotspot. Biodiversity and Conservation 17: 2323-2338.
Osinga N, Hart P, Morick D, (2008) By-catch and drowning in harbour porpoises (Phocoena phocoena) stranded on the northern Dutch coast. Eur J Wild Res 54: 667-674.
Herr H, Fock HO, Siebert U, (2009) Spatio-temporal associations between harbour porpoise Phocoena phocoena and specific fisheries in the German Bight. Biol Conserv 142: 2962-2972.
Siebert U, Joiris CR, Holsbeek L, Benke H, Failing K, et al. (1999) Potential Relation Between Mercury Concentrations and Necropsy Findings in Cetaceans from German Waters of the North and Baltic Seas. Marine Pollution Bulletin 38: 285-295.
Bennett PM, Jepson PD, Law RJ, Jones BR, Kuiken T, et al. (2001) Exposure to heavy metals and infectious disease mortality in harbour porpoises from England and Wales. Environmental Pollution 112: 33-40.
Beineke A, Siebert U, McLachlan M, Bruhn R, Thron K, et al. (2005) Investigations of the Potential Influence of Environmental Contaminants on the Thymus and Spleen of Harbor Porpoises (Phocoena phocoena). Environ Sci Technol: 3933-3938.
Pierce GJ, Santos MB, Murphy S, Learmonth JA, Zuur AF, et al. (2008) Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: Geographical trends, causal factors and effects on reproduction and mortality. Environmental Pollution 153: 401-415.
Weijs L, Dirtu AC, Das K, Gheorghe A, Reijnders PJH, et al. (2009) Inter-species differences for polychlorinated biphenyls and polybrominated diphenyl ethers in marine top predators from the Southern North Sea: Accumulation patterns in harbour seals and harbour porpoises. Environmental Pollution 157: 437-444.
Madsen PT, Wahlberg M, Tougaard J, Lucke K, Tyack P, (2006) Wind turbine underwater noise and marine mammals: implications of current knowledge and data needs. Marine Ecology Progress Series 309: 279-295.
Gilles A, Scheidat M, Siebert U, (2009) Seasonal distribution of harbour porpoises and possible interference of offshore wind farms in the German North Sea. Marine Ecology Progress Series 383: 295-307.
Daniel P, Jan G, Cabioc'h F, Landau Y, Loiseau E, (2002) Drift Modeling of Cargo Containers. Spill Science & Technology Bulletin 7: 279-288.
Ihaka R, Gentleman R, (1996) R: a language for data analysis and graphics. J Comput Sta Graph Anal 5: 299-314.
Cowpertwait PSP, Metcalfe AV (2009) Introductory Time Series with R. Berlin: Springer. 254 p.
Zeileis A, Leisch F, Hornik K, Kleiber C, (2002) strucchange: An R Package for Testing for Structural Change in Linear Regression Models. Journal of Statistical Software 7: 1-38.
Hammond PS, Berggren P, Benke H, Borchers DL, Collet A, et al. (2002) Abundance of harbour porpoises and other cetaceans in the North Sea and adjacent waters. Journal of Applied Ecology 39: 361-376.
Hammond PS, MacLeod K, Berggren P, Borchers DL, Burt L, et al. (2013) Cetacean abundance and distribution in European Atlantic shelf waters to inform conservation and management. Biological Conservation. In press.
Fontaine MC, Baird SJE, Piry S, Ray N, Tolley KA, et al. (2007) Rise of oceanographic barriers in continuous populations of a cetacean: the genetic structure of harbour porpoises in Old World waters. BioMed Central Biology 5: 30-46.
Camphuysen KCJ, Smeenk C, Addink MJ, Van Grouw H, Jansen OE, (2008) Cetaceans stranded in the Netherlands from 1998 to 2007. Lutra 51: 87-122.
Jung J-L, Stephan E, Louis M, Alfonsi E, Liret C, et al. (2009) Harbour porpoises (Phocoena phocoena) in north-western France: aerial survey, opportunistic sightings and strandings monitoring. Journal of the Marine Biological Association of the United Kingdom 89: 1045-1050.
Strong DR, (1980) Null hypothesis in Ecology. SYNTHESE 43: 271-285.
Clarke KR, Somerfiled PJ, Gorley RN, (2008) Testing of null hypotheses in exploratory community analyses: similarity profiles and biota-environment linkage. Journal of Experimental Marine Biology and Ecology 366: 56-69.
Costa de Azevedo MC, Gerson Araùjo F, Machando Pessanha AL, De Araùjo Silva M, (2006) Co-occurrence of demersal fishes in a tropical bay in southeastern Brazil: A null model analysis. Estuarine Coastal and Shelf Science 66: 315-322.
Coelingh JP, Van Wijk AJM, Holtslag AAM, (1996) Analysis of wind speed observations over the North Sea. Journal of Wind Engineering and Industrial Aerodynamics 61: 51-69.
Siegismund F, Schrum C, (2001) Decadal changes in the wind forcing over the North Sea. Clim Res 18: 39-45.
Camphuysen KCJ, (2004) The return of the harbour porpoise (Phocoena phocoena) in Dutch coastal waters. Lutra 47: 113-122.
Thomsen F, Laczny M, Piper W, (2006) A recovery of harbour porpoises (Phocoena phocoena) in the southern North Sea? A case study off Eastern Frisia, Germany. Helgoland Marine Research 60: 189-195.
Robinson KP, Baumgartner N, Eisfeld SM, Clark NM, Culloch RM, et al. (2007) The summer distribution and occurrence of cetaceans in the coastal waters of the outer southern Moray Firth in northeast Scotland (UK). Lutra 50: 19-30.
Weir CR, Stockin KA, Pierce GJ, (2007) Spatial and temporal trends in the distribution of harbour porpoises, white-beaked dolphins and minke whales off Aberdeenshire (UK), north-western North Sea. Journal of the Marine Biological Association of the United Kingdom 87: 327-338.
Kiszka J, MacLeod K, Van Canneyt O, Walker D, Ridoux V, (2007) Distribution, encounter rates, and habitat characteristics of toothed cetaceans in the Bay of Biscay and adjacent waters from platform-of-opportunity data. ICES Journal of Marine Science 64: 1033-1043.
McLeod K, Brereton T, Martin C, (2009) Changes in the occurrence of common dolphins, striped dolphins and harbour porpoises in the English Channel and Bay of Biscay. Journal of the Marine Biological Association of the United Kingdom 89: 1059-1065.
Maldini D, Mazzuca L, Atkinson S, (2005) Odontocete stranding patterns in the main Hawaiian Islands (1937-2002): How do they compare with live animal surveys? Pacific Science 59: 55-67.
