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determinate of relative abundance and not season. Bottlenose
dolphins were most likely to be observed in the west, with
greatest relative abundance also observed in the west.
Region
Log Abundance/min
Figure 100. Abundance (± SE) of common bottlenose dolphin
in each region.
Common bottlenose dolphin
The common bottlenose dolphin is widespread and abundant
in inshore waters and was recorded at eight of the 14 sites
and in all regions. Greatest relative abundance was reported
from Dunree Head, Downpatrick Head, Loop Head and Slea
Head, though data from Dunree and especially Downpatrick
Heads were constrained by small number of watches relative
to Loop and Slea Heads. This shows that region is the main
Autumn
Summer
Spring
Winter
Short-beaked common dolphin
The short-beaked common dolphin was recorded at seven
sites, with six of these between Hook Head and Loop Head
and none in the east and at only one site in the northern
region. Seasonal and regional trends were consistent across
years. In the south, the abundance was similar in autumn and
winter but greater than in spring and summer, which showed
the lowest abundance. In the west, short-beaked common
dolphins were more abundant in the summer, followed by
autumn and spring, and were lowest in the winter. Shortbeaked
common dolphin numbers in the south and west
varied greatly between locations. They were occasionally seen
in the north, but only at Malin Beg. The greatest abundance of
short-beaked common dolphins was in 2005 and 2007 off the
south coast and in 2007 off the west coast. There were
consistently high numbers in the southern region, with a yearly
oscillation. Short-beaked common dolphin abundance has
declined in the two regions they are regularly recorded in
(south and west coast) during 2009 following a peak in 2007.
Risso’s dolphin
Risso’s dolphin was recorded at six sites. It was infrequently
recorded but found off all coasts but only in small numbers.
The highest relative abundance was off Downpatrick Head,
Portmuck Island, Galley and Slea Heads. Risso’s dolphins
were most commonly seen in summer and none were
observed in winter. There was a seasonal component to
Risso’s dolphin abundance in all regions surveyed.
Region
Log Abundance/min
Figure 101. Abundance (± SE) of common dolphin in each
region and season.
Irish Cetacean Review 2000-2009
Figure 102. Change in common dolphin abundance (log
abundance/min) by region over time (years). Squares = north,
diamonds = east, triangles = south, and crosses = west.
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