Status of harbour seals (<i>Phoca vitulina</i>) in mainland Norway

Abstract

Harbour seals were counted along the entire Norwegian coast at known moulting haulout sites in the period mid-August to early September 2003-2006. In 2003-2005, almost all known moulting areas from Finnmark to Vestfold counties were covered by aerial photo surveys flown at altitudes of approximately 800-900 ft (243-274m), and at low tide (± 2 hours). Surveys in the Østfold County were flown in 2003-2006 at 300 ft (91m), and the small tidal amplitudes permitted counts to be carried out irrespective of the tidal cycle. In some sub-areas, two or three independent surveys were conducted. Visual counts using binoculars from smaller boats and islands were carried out in some selected areas. The surveys revealed a total minimum population of 6,705 harbour seals in Norwegian waters. Harbour seals were most abundant in the Nordland and Sør-Trøndelag counties with minimum estimates of approximately 2,500 and 1,500 seals, respectively. The presented minimum estimate is approximately 800 seals lower than an estimate obtained in a comparable study carried out during the moult in 1996-1999. Increased anthropogenic removals, and the phocine distemper virus (PDV) epidemic in the Skagerrak region in 2002, may have contributed to the current lower estimate.

Keywords

• harbour seals
• Norway
• surveys
• abundance