The status of harbour seals (<i>Phoca vitulina</i>) in the United Kingdom

Abstract

The UK holds approximately 40% of the European harbour seal population, with the majority found around the coasts of Scotland. Harbour seal populations in the UK have been monitored through a series of repeated aerial surveys of animals hauled out during the annual moult in early August. This moult count is used as a consistent index of population size. Survey methods and frequencies vary. The Scottish and English east coast populations mainly haul out in tidal estuaries and are surveyed annually, using fixed wing aircraft and digital photography. Populations in north and west Scotland often haul out on rocky shores and are surveyed less frequently, using helicopters fitted with thermal imagers. Overall, the most recent minimum estimate of the UK harbour seal population is 24,250 seals of which 19,800 are in Scotland, 3,200 in England and 1,250 in Northern Ireland. The results show that the number of harbour seals in eastern England was increasing before the 1988 and 2002 phocine distemper (PDV) epizootic but has not increased since the end of the 2002 epizootic. There is also evidence of a general decline in most of the large harbour seal colonies around Scotland. The populations along the north and northwest mainland coast were an exception, with numbers appearing to be stable. Between 2001 and 2008, the population in Orkney declined by 67% and Shetland declined by 40%, indicating harbour seals in these areas experienced substantially increased mortality or very low recruitment over this period. The widespread declines, ranging from Shetland to The Wash, suggest that the causes may have been present over a large part of the North Sea and waters off western Scotland.Thompson, D., Duck, C.D. and Lonergan, M.E. 2010. The status of harbour seals (Phoca vitulina) in the United Kingdom. NAMMCO

The status of harbour seals (Phoca vitulina) in the UK

“…Aerial surveys of the UK harbour seal population have been carried out regularly since the late 1980s with some irregular and sparse monitoring in South-East England as far back as the late 1960s (Lonergan et al, 2007;Thompson, Duck, & Lonergan, 2010;Thompson, Lonergan, & Duck, 2005,). Lonergan et al (2007) presented UK-wide results of surveys up to 2005.…”

Rescaling of aerial survey data with information from small numbers of telemetry tags to estimate the size of a declining harbour seal population

“…The Orkney Islands, off northern Scotland, used to contain one of the largest concentrations of harbour seals ( Phoca vitulina ) in Europe (Thompson et al , ). The numbers of animals counted during aerial surveys of this area decreased by 65% over the period 2001–2010 (data shown in Table ).…”

Introduction: The harbour seal (<i>Phoca vitulina</i>) - a global perspective

“…In the Wash, the 1988 epizootic resulted in 52% drop in the population followed by a rapid recovery, until the 2002 epizootic resulted in 22% drop in the population. In contrast to the recovery after the first epizootic, and different to most other areas affected by the 2002 epizootic, the population in the Wash has continued to decline (Thompson et al 2010). A decline in harbour seal abundance since the late 1990`s is also observed in Orkney, Shetland, and, but to a lesser extent, in the Outer Hebrides and east Scotland.…”

“…In this view they solicited a manuscript on seal rehabilitation (see Osinga and 't Hart 2010). Furthermore, as rapid declines of harbour seal abundance with unknown causal relations are observed in some areas (see Thompson et al 2010), but the role of anthropogenic factors in these rapid population changes is not known, some hypotheses are discussed towards the end of this chapter.…”