Seals 2004 Common Seals in the Wadden Sea in 2004 Common Wadden Sea Secretariat, Wilhelmshaven October 2004 1999  / 2000 / 2001 / 2002 / 2003 / 2004/05 / 2006 / 2007 (PDF format) 1999 / 2000 / 2001 / 2002 / 2003 / 2004 / 2005 / 2006 / 2007 (html format) Counting Harbour Seals in the Wadden Sea in 2004 - Expected and Unexpected Results  Following the trilateral Seal Management Plan, harbour seals in the Wadden Sea are monitored annually by a series of five aerial surveys. Last year’s census has shown the extent of the 2002 distemper mass mortality. The 2004 counting data document the first step of the recovery of the seal stock. In the peak moulting season in early August, maximum numbers of seals counted in the Wadden Sea were 3,194 in the Netherlands (NL), 3,098 in Lower Saxony (LS)/Hamburg, 5,032 in Schleswig-Holstein (SH), and 1,479 in Denmark (DK), a grand total of 12,803 seals. Maximum figures of newborn seals counted during the late pupping season in late June / early July make up a grand total of 3,704, with 694 in NL, 946 in LS, 1,781 in SH, and 283 in DK (the latter may be biased downwards due to an early count date). The total number of seals counted is 18% higher than the 2003 result, which compares to the pre-epizootic average growth rate of 12-13% per year. Of course, year-to-year records can differ from the actual growth rate due to random or methodological effects. The figure of 18% in fact remains within the previous range of annual changes in counts from the moulting season. However, we actually did expect an elevated stock increase after 2003 (see WSNL 2003-2, page 11). This was based on evidence of a temporary surplus of adult female seals at least in part of the population caused by the mass mortality in 2002. An elevated proportion of females in turn means elevated productivity, as was in fact observed in 2003. It is emphasized that we do not relate high productivity to lowered seal density. Although population size had increased by a factor of five between 1989 and 2002, fertility of seals is considered stable throughout that period. Surprisingly, productivity appears even higher in 2004 than in 2003: The counted number of newborn seals is by as much as 25% higher than in 2003, and the ratio between the count of newborns and the total count in August (which contains only very few pups of the year) is 29%, comparing to 27% in 2003. Due to the presumably high recruitment of young seals born in 2003, which do not contribute to the 2004 pup production, we had rather expected a lower per capita birth rate this year. Of course, count results do not precisely reflect birth rate or changes thereof. For instance, the fraction of seal pups born in a year that is actually counted may be influenced by the temporal spread of births, the average length of lactation, and survey dates. Nevertheless, certain demographic effects related to the 2002 seal epidemic (i.e. skewed sex ratio amongst survivors, certain rate of reproductive failure in 2002) are considered in order to explain recent count results. In any case, harbour seals are likely to recover quickly from the blow in 2002. Assuming a current growth rate around 18% per year, which may level off to the normal 12-13% within three years or so, rebuilding of the 2002 stock size may be expected at least until 2008. Trilateral Seal Expert Group (TSEG) Kai F. Abt, Consultant, Schleswig-Holstein, Germany, Sophie M.J.M. Brasseur, Alterra-Marine & Coastal Zone Research, Texel, The Netherlands, Peter J.H. Reijnders, Alterra-Marine & Coastal Zone Research, Texel, The Netherlands,  Ursula Siebert, FTZ-Büsum der Universität Kiel, Schleswig-Holstein, Germany, Michael Stede, LAVES Cuxhaven, Lower Saxony, Germany, Svend Tougaard, Fiskeri- og Søfartmuseet, Esbjerg, Denmark.     Figure 1: Number of Counted Seals in the Wadden Sea since 1975   Home | Trilateral Cooperation | News/Service | Management | Monitoring | Interregional Cooperation