What's to be seen outside south coast "hotspots"?

20th Nov 2013

Ok, so we all know that we’re in the middle of what is loosely termed the “large whale season”, which means we are receiving almost daily sightings of fin and/or humpback whales along the Irish south coast counties of Cork and Waterford. This has been well documented by IWDG over the years, and some, both inside and outside IWDG, would say that it’s a drum that we’ve been beating too long and too loud.  This review seeks to analyse what’s been seen around the rest of country during the period September to November 2013.

Using the advanced search option on www.iwdg.ie during the period 1st Sept – 19 Nov 2013 IWDG received and validated 274 cetacean sighting records from all regions. Of these 244 (89%) were allocated to the 7 species (Table 1). Both the species number and mix change significantly if we remove sightings data from the 3 counties of Kerry, Cork and Waterford. The total number of sightings when we remove the three south coast counties falls to 87, a reduction of 68%, and the number of species falls from seven to five, a drop of 29%. Clearly in removing the south coast data we start telling a very different story about how cetaceans use our inshore waters.

 

Table 1

 

All Areas

Leinster, Ulster & Connaught

Species

No. Sightings

%

No. Sightings

%

Harbour porpoise

73

27

49

56

Common dolphin

55

20

5

6

Minke whale

45

16.4

2

2.3

Bottlenose dolphin

26

9.5

22

25

Fin whale

23

8.4

1

1

Humpback whale

17

6.2

0

0

Risso’s dolphin

3

1

0

0

 

Table 1 above demonstrates a clear distinction between inshore and offshore species. For instance the harbour porpoise and bottlenose dolphins both have a preference for inshore waters and make up a higher % of sightings in waters outside the south coast. Our smallest and most frequently recorded cetacean the harbour porpoise represents 27% of all cetacean sightings in “all Irish” inshore waters, but this doubles to 56% by removing the south coast data, suggesting a higher relative abundance in other areas. 

Map 1. Cetacean sightings Sept-Nov 2013 (Excluding Munster) © IWDGA glance at the blue dots (Hbr porpoise) on Map 1 (left) suggests many of these sightings are coming from the Dublin Bay area and Counties Down and Antrim.  As the majority of these sightings are “casual observations” from the general public, it is best to avoid over-interpreting the data. For instance you could argue that Dublin and Belfast are our two largest population centres and that we’d reasonably expect more porpoise records from these areas as a result of increased “observer effort”. But neither should we dismiss the value of sightings data from “Citizen Scientists”.  The strong showing of porpoises on this map in the Dublin Bay area is entirely consistent with the results of two dedicated boat-based harbour porpoise surveys carried out by IWDG in 2008 and 2013. There are clearly lots of porpoises along the Dublin coast, and this is quite accurately detected by the recording scheme.  So please, the next time you’re walking out to the Baily lighthouse on Howth or strolling along Dun Laoghiare pier, keep an eye out for our smallest whale, and report them to IWDG.

  Bottlenose dolphins, Kilcummin Head, Co. Mayo © Caroline Tuffy, IWDG

An even more pronounced trend can be seen with the bottlenose dolphin; they rank 4th on an all-Island basis with 9.5% of sightings, but again when the south coast data is removed this changes to 2nd place, with an almost three-fold increase to 25% of sightings. During the period of this summary bottlenose were absent along the entire south and east coast. In fact of the 26 sightings, 20 (77%) were from Ulster and almost all of these were from Counties Antrim and Donegal. Yes, it’s only a small sample size, but it does accurately reflect their distribution on an annual basis. Once again however we urge caution and never was the old adage about …..“absence of evidence not equating to evidence of absence” so apt. For instance there is no doubt that the lack of sighting reports from the Galway Bay area reflects more on the areas low lying topography than any lack of cetacean activity.

Alas, when it comes to the pelagic dolphins like the short-beaked common dolphin and all whale species we see a reversal of the above trend, i.e. once the south coast data is removed common dolphin sightings are reduced by 70%, minke whale sightings plummet from 16.4% to 2.3%, and the large whales (fin and humpbacks) practically vanish off the map.  But again we are fortunate that when these rare sightings do occur they are detected by the sighting scheme.

Minke whale, Mullaghmore, Co. Sligo © Sean CrankshawA case in point was a run of minke whale sightings this week from Brinlack Bay, south of Bloody Foreland, Co. Donegal. While discussing this observation with Gareth Doherty he commented quite casually that he also reported similar activity to IWDG this time last year.  Curious, I checked the database and there it was… within the same week, the same species and same numbers showed in the exact same area. Now of course this could be a fluke (excuse pun) but I don’t believe in flukes, especially when it comes to minkes, because we all know that minkes don’t fluke….right?. But they are creatures of habit.

I’ve always said that a once off sighting is just that, an event, but if you see something similar the following year, then you are entitled to suspect something more significant, and if you record it a 3rd year running, then you can start shouting about it from the roof tops, as you probably have a trend.  So we’ll just have to wait and see if this activity is observed again off Bloody Foreland in November 2014. And wouldn’t it be nice to hear about something other than fin and humpback whales in November off West Cork?  Roll on the annual November minke gathering off the Northwest….I like it already.

 

By Pádraig Whooley

IWDG Sightings Coordinator