Changes in coastal site usage by bottlenose dolphins (Tursiops truncatus) in Cardigan Bay, Wales

摘要

A shore-based study has been conducted for over 14 years of a coastal population of bottlenose dolphins (Tursiops truncatus) that frequent New Quay Bay. Analysis of year-round observations for the years 1997, 2001, and 2002 are presented for the first time and are set in context with results from the years 1989-1996 and 1998-2000, which were the subject of earlier papers. The annual frequency of dolphin sightings in days per year were comparable with previous studies. The results for 1997 are in line with observations made in the period 1989 to 1999, both in terms of group size frequency distribution, average monthly group size, and number of sightings of groups with small calves. The results for 2001 and 2002 confirm the significant decline in dolphin group size first noted in the year 2000, with a steep decline in both average monthly group size and monthly maximum group size. In addition, there was a corresponding decline in the incidence of groups containing small calves. In 2002, the number of recognised individuals seen was also reduced.