DOI: 10.5061/dryad.1hv28
title: Data from: Spatio-temporal modelling of auk abundance after the Erika oil spill and implications for conservation

description: Species distribution models are widely used in applied ecology and
 conservation. While accounting for spatial dependences is now the rule,
 temporal dependences have rarely been dealt with explicitly. In this
 study, we analyse wintering auk distribution in the Bay of Biscay and
 English Channel and estimate changes in abundance within and between years
 while accounting for space–time dependencies. We then propose a
 retrospective estimate of the impact of the Erika oil spill that occurred
 in December 1999. Two series of extensive aerial surveys, repeated at
 intervals of 1–2 months, were carried out at a 10-year interval off the
 French Atlantic coast (2001–2002 and 2011–2012). Spatially and temporally
 explicit Bayesian models were fitted to these data to provide
 spatio-temporal predictions of auk abundance. These were then used to
 compare abundances within the area affected by the Erika oil spill two and
 twelve years after the catastrophe. The results showed that 1·55 million
 auks wintered in the study area in 2011–2012. The main wintering area was
 the English Channel (more than one million auks) but the Bay of Biscay
 also became an important area in the middle of winter (470 000 auks) owing
 to a strong southward shift in auk distribution. Two years after the
 catastrophe (2001–2002), the area affected by the Erika oil spill hosted a
 small proportion of auks of the Bay of Biscay – about 80 000 individuals.
 This number increased by more than three times 10 years later and reached
 270 000 individuals, whereas no significant change was detected elsewhere.
 We suggest that it could result from a recovery after the extra-mortality
 induced by the Erika oil spill. Policy implications. This study identified
 major auk wintering areas, with abundances much higher than previously
 realized. Oil spills have occurred regularly in these areas, with major
 delayed impacts on auk breeding populations. The worst case scenario would
 be if a major oil spill occurred in the English Channel in February, when
 abundance reaches one million auks. Although such a disaster has not so
 far occurred, stricter policies on the transport of hydrocarbons should be
 implemented to prevent such a possibility.
description: The SAMM data
 (RData)The 2011-2012 data
 analysed in this paper. List of variables: POSIX.time: Date and hours of
 the counts; GroupTime: Group of time used for analysis (see paper);
 SeaState: Sea state at Beaufort scale; CloudCover: Cloud cover from 0 to
 8; GlareSeverity: Glare severity from 1 to 3 (0 when no glare); GlareArea:
 Width of the glare in degree (from 0 to 220°, see paper); DistCoast:
 Distance from the coast in kilometers; AtlanticArea: Atlantic (1) vs.
 English Channel (0) area; Alcides: Number of auks counted within segments
 from both sides; SegmentLength: Length of the segment in
 meters.data.SAMM.RDataThe ROMER data (RData)The 2001-2002 data analysed in this paper. List of variables: MonthfromOctober: ID of month from October 2001, e.g. 2 stands for November 2001; Alcides: Number of auks counted within 5km segments from the side without glare; SeaState: Sea state at Beaufort scale; CloudCover: Cloud cover from 0 to 4; DistCoast: Distance from the coast in kilometers.data.ROMER.RDataSmall pelagic fish data (Appendix S6)The data used in Appendix S6 (from ICES).AppendixS6_data.xls