summer distribution and relative abundance of …summer distribution and relative abundance of...

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ShOp Surveys Unit

Irish Whale and Dolphin Group

Merchant’s Quay, Kilrush, Co. Clare

Common Dolphins (© Dave Wall 2004)

IWDG Heritage Council Report 2004 Page 1 26/11/2004

Summer Distribution and Relative Abundance of Cetaceans off the West Coast of Ireland

A Report for the Heritage Council

By

Dave Wall

ShOp Surveys Unit

Irish Whale and Dolphin Group

Merchants Quay, Kilrush, Co. Clare.

Email: [email protected] Web: www.iwdg.ie/shopsurveys/

Survey Team

Dave Wall (Project Director)

Joanne O’Brien

John Meade

Brendan Allen


Index

Summary …………………………………………………………………………………...........................................

1. Introduction ………………………………………………………………………………………………………………

2. Methods

2.1 Survey Methods …………………………………………………...…...................................................

2.2 Data Recording ………………………...…………… …………………………………………………..

2.3 Data Analysis …………………………………………..…………………………………………………..

3. Results

3.1 Survey Leg Reports …………………………….………………...…...................................................

3.1.1 Leg 1 - Shannon Approaches…………….…………………………………………………

3.1.2 Leg 2 - North Coast……………………………………. ……….………………...…………

3.1.3 Leg 3 - Rockall Bank …………………...….………..……..……………………...…………

3.1.4 Leg 4 – North Coast ……………………………….……....……………………...…………

3.1.5 Leg 5 – Cork/Kerry Coast ……………...………….……....……………………...…………

3.2 Cetacean Species Distribution & Relative Abundance …………………………..............................

3.2.1 Survey Effort ……………………………….…………………………………………………

3.2.2 Species Distribution & Relative Abundance ………………………………………………

3.2.2.1 Common Dolphin (Delphinus delphis) ………………………………………

3.2.2.2 Atlantic White-Sided Dolphin (Lagenorhynchus acutus) ……………….…

3.2.2.3 Bottlenose Dolphin (Tursiops truncatus) ……………………………………

3.2.2.4 Harbour Porpoise (Phocoena phocoena) ………..…………………………

3.2.2.5 Risso’s Dolphin (Grampus griseus) …………………………………………

3.2.2.6 Pilot Whale (Globicephala melanea) ……..…………………………………

3.2.2.7 Minke Whale (Balaenoptera acutorostrata) ………...………………………

3.2.2.8 Fin Whale (Balaenoptera physalus) …………………………………………

3.2.2.9 Unidentified Dolphin Species …………………………………………………

3.2.2.10 Unidentified Whale Species …………………………………………………

3.2.2.11 Basking Shark (Cetorhinus maximus) ………..……………………………

3.2.2.12 Other Species …………………………………………………………………

4. Conclusions ……………………………………………………………………………………………………..

5. Acknowledgements …………………………………………………………………………………………….

6. References ……………………………………………………………………………………………………….

Appendix I : List of cetacean species recorded in Irish waters .………………………………………………………..

Appendix II : Daily Wind Speed and Directions Recorded During Each Leg of the Survey ………………………..

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Summary

From May to September 2004 the Irish Whale and Dolphin Group conducted a survey of

cetacean (whale, dolphin and porpoise) distribution and relative abundance (abundance per

unit effort) on board the State offshore research vessel, R.V. Celtic Explorer. The survey was

operated as an ancillary project of the Geological Survey of Ireland’s National Seabed Survey

and facilitated by the Irish Marine Institute.

Eight species of cetacean were identified in the survey area: Common Dolphin (Delphinus

delphis), Atlantic White-sided Dolphin (Lagenorhynchus acutus), Pilot Whale (Globicephala

melas), Harbour Porpoise (Phocoena phocoena), Risso’s Dolphin (Grampus griseus),

Bottlenose Dolphin (Tursiops truncatus), Minke Whale (Balaenoptera acutorostrata) and Fin

Whale (Balaenoptera physalus).

The most abundant cetacean species over the Irish shelf was the common dolphin reaching a

maximum relative abundance of 17.5 animals per hour (aph) off the west Cork coast. In

offshore waters over the Rockall Bank, the Atlantic White-sided dolphin was the most abundant

species, reaching a maximum density of 14.5aph over the southern end of the bank (see

relative abundance results).

The relative abundance of cetacean species off the north Donegal and Derry coasts was

extremely low, despite the highest survey effort being focused on these areas. Surveys

conducted in the same areas during autumn and winter 2003/2004 also recorded low cetacean

relative abundance in these areas and further survey effort is required in order to determine

whether cetacean abundance off the north coast remains at such a low level all year round.

This was the first major offshore cetacean survey conducted on the west coast by the IWDG as

part of its Ships of Opportunity (ShOp) survey programme. The data from this survey has

begun to highlight major differences in species occurrence and relative abundance between

the north and south coasts and between offshore banks and the Irish shelf itself.

The results of this survey have shown that surveys of distribution and relative abundance,

conducted on board ships of opportunity, provide a cost effective and practical method of

monitoring cetacean population in Ireland’s offshore habitats. Further effort is required to

identify seasonal trends and to examine the effects of bathymetry, food availability and other

oceanographic factors on cetacean distribution and abundance. Future survey effort should be

promoted on board platforms of opportunity such as research vessels and naval vessels to

achieve year-round monitoring of seasonal and multi-annual trends in cetacean distribution and

relative abundance in Irish waters.


1. Introduction

The waters of Ireland’s Exclusive Economic Zone (EEZ) represent one of the most important

cetacean (whales, dolphins and porpoise) habitats in Europe. To date 24 species of cetacean

have been recorded in Irish waters (see appendix I).

All cetacean species in Irish waters are protected by the 1976 Wildlife Act 20 (and Wildlife

Amendment Act 2000 21) and Irish waters, including the EEZ were declared a whale and

dolphin sanctuary in 1991. All cetacean species are protected under the EU Habitats Directive 22 and the harbour porpoise and bottlenose dolphin are listed under Annexe II of the habitats

directive, requiring the designation of Special Areas of Conservation (SACs) for their

protection.

As part of the 2004 Seabed Survey conducted by the Geological Survey of Ireland and the

Marine Institute, the Irish Whale and Dolphin Group (IWDG) conducted an ancillary survey of

cetacean distribution and relative abundance on board the R.V. Celtic Explorer.

IWDG Ships of opportunity Surveys (ShOp Surveys)

The IWDG has operated a cetacean strandings 1 and sightings 2 recording scheme in Ireland

since 1991. Data from these schemes has highlighted the distribution and relative abundance

of cetacean species in inshore waters but have provided limited knowledge of the occurrence

of cetaceans in offshore habitats.

In order to increase knowledge of cetacean distribution and abundance in offshore habitats, the

IWDG ShOp Surveys Unit has conducted surveys on board commercial ferries in the Irish Sea,

Celtic Sea and English Channel since 2001. IWDG Ferry Surveys now form part of a European

collaboration of researchers conducting surveys on board ferries from Ireland, Scotland, Wales,

England, Spain and Holland.

The Atlantic Research Coalition (ARC) combines data sets from member groups to gain a

greater knowledge of the occurrence of cetaceans in Northwest European waters. The data

generated enables the description of cetacean distribution and calculation of monthly, seasonal

and annual abundance indices. Data of this type have the potential to identify early signs of

population change or other factors of conservation concern. Such surveys also have the

potential to evaluate the effectiveness of protected area designations and conservation/policies

in conserving cetaceans 3.

There have been a number of offshore surveys in Irish waters previously 4-11 although not all of

these have been dedicated cetacean surveys, many focusing on seabirds with incidental

records of cetaceans. In addition to this there have been a number of acoustic surveys for

cetaceans 12-14 which have supplied data on distribution but are limited in their ability to provide

abundance data.


The knowledge of cetacean distribution and abundance in Irish offshore habitats is poor and it

is with the goal of significantly increasing this knowledge that the current study was conducted.

The majority of cetacean offshore surveys in Irish waters, as with the current survey, have

focused on the summer months. The current survey will, however, form part of a wider

database of distribution and relative abundance surveys conducted by the IWDG ShOp

Surveys Unit in all seasons since 2001 and into the future. Already the IWDG has a three year

database for the Irish Sea and eastern Celtic Sea. In addition to this surveys conducted

onboard the Celtic Explorer in autumn/winter/spring 2003/2004 and planned surveys for the

coming autumn/winter will significantly increase knowledge on the distribution and abundance

of cetaceans during these rarely surveyed seasons.

The objectives of this survey were to:

1. Determine the relative abundance and distribution of cetacean species within the

survey areas covered by the 2004 National Seabed Survey and in areas covered en

route to and from these survey areas.

2. Produce relative abundance and distribution data comparable to the data collected by

the IWDG on their Ferry Surveys and other surveys conducted by the ShOp Surveys

Unit on board the R.V. Celtic Explorer. All data to be fed into the main IWDG sightings

database and used to produce maps of cetacean relative abundance and distribution

for Irish waters.


2. Methods

2.1. Survey Method

This survey was conducted from the observation platform located above the bridge and

18m above the waterline (fig. 1).

Watch effort was focused on the area dead ahead of the vessel and 45? to either side. The

area was constantly scanned during these hours by eye and with binoculars. Sightings

recorded up to 90? either side of dead ahead were included in the survey results.

2.2. Data Collection

Ships position, course and speed were recorded using a Garmin 72™ GPS linked to a

Toshiba laptop PC. At the end of each day the track data was downloaded onto the laptop

PC using Garmin MapSource™ plotting software. Environmental stations were recorded

every 15 minutes using the IFAW Logger 2000™ program 23 and later transferred to a

Microsoft Excel spreadsheet. Environmental data gathered were: sea state; visibility; cloud

cover; swell height; precipitation; wind speed & wind direction.

Sightings were also logged using the IFAW Logger 2000™ program. For each sighting the

following data were recorded: time; location; species; distance; bearing; number of animals

(adults, juveniles and calves) and behaviour.

2.3. Data Analysis

Sightings data were separated into two categories; 1) Effort-related – sightings collected

while conducting surveys from the crow’s nest. 2) Auxiliary sightings – collected outside

Fig. 1. R.V. Celtic Explorer (Left) showing the purpose built Crow’s Nest located above

the bridge (Right).


survey hours e.g. while working on the bridge or while on breaks etc. Both effort-related

and auxiliary sightings were used to plot distribution maps for each species.

Survey effort was allocated to grid squares 1o latitude X 1o longitude. Effort was allocated

to grids based on location data collected at each environmental station. Sightings were

also allocated to grid squares based on the sighting location data. Relative abundance

figures for each species were calculated as:

Relative Abundance = Total No. of animals sighted per grid square

Total Effort (hrs) per Grid Square

Maps were prepared using ArcView GIS software (version 3.3).


3. Results

3.1. Survey Leg Reports

3.1.1. Leg 1 – Shannon Approaches (11 May – 2 June 2004)

3.1.1.1. Environmental Conditions

Weather conditions during leg 1 varied with conditions being better during the first

half of the leg. Sea state was favourable for less than half of the survey time. Sea

state was recorded at 3 or less for 48% of the environmental stations. Precipitation

occurred at 29.4% of the environmental stations but visibility was only significantly

restricted (<1km) for 1.5% of the survey period. Swell height was severe (2m+) at

28.7% of the environmental stations (fig. 2).

3.1.1.2. Cetacean Survey Results

In all 56.58 hours of survey time was achieved (fig. 3). The level of cetacean

activity recorded during this survey was high but with low species diversity.

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Sea State (0 - 10)

Swell (1 - 3)

Wind Speed (knots)

Fig. 2. Sea state, swell conditions and wind speed recorded twice daily during the survey.

Fig. 3. Survey effort at sea state = 3 recorded during Leg 1. Survey effort was recorded for

3 grid squares (A–C).


Three species of cetacean were recorded; common dolphin (Delphis delphis),

bottlenose dolphin (Tursiops truncatus) and minke whale (Balaenoptera

acutorostrata) (table 1). A number of sightings of unidentified dolphin species and

small whale species were also made (figs. 4&5). It was thought probable that

multiple sightings of a breaching, brown coloured, small whale was of a northern

bottlenose whale (Hyperoodon ampullatus). In addition to cetacean species, there

were also sightings of grey seal (Halichoerus grypus) and basking shark

(Cetorhinus maximus).

The majority of the common dolphin sightings occurred between 10km and 40km

offshore in 40 – 90m of water with no sightings occurring within 10km of the coast.

Species Grid Cell

Relative Abundance (Animals per Hour)

Bottlenose Dolphin (Tursiops truncatus) A 0.44

Common Dolphin (Delphinus delphis) A 2.23

Minke Whale (Balaenoptera acutorostrata) A 0.04

UnID Dolphin Species A 7.60

Table 1. Relative abundance of cetacean species in survey grid cell A. No Cetaceans were recorded in

survey grid cells B or C.

Fig. 4. Survey effort and cetacean sightings recorded en route to survey location and

on site during leg 1.


3.1.1.3. Birds Recorded

Twenty one different bird species were recorded during this survey: Great Skua

(Occ), Brown Guillemot (Com), Cormorant (Com IS), Collared Dove (Sh), Common

Tern (Com), Roseate Tern (Occ), Cory’s Shearwater (Si), Fulmar (Com), Gannet

(Com), Greater Black Backed Gull (Com), Lesser Black Backed Gull (Com),

Kittiwake (Com), Herring Gull (UnCom), Manx Shearwater (Num), Puffin (Occ),

Razorbill (Com), Shag (Com IS), Storm Petrel (Com OS), Swallow (Sh), Whimbrel

(Si).

[Occ – Occassional; Com – Common; Com IS – Common Inshore; Sh – Ship

Bound Birds; Si – Single sightings; UnCom – Uncommon; Num – Numerous; Com

OS – Common Offshore].

3.1.1.4. Discussion

The level of cetacean activity during the course of this survey was relatively high.

Throughout the survey large numbers of shearwaters and gannets were present

feeding in the area. Most of the seabird and cetacean activity was located offshore

(10km +) with very little inshore activity. The distribution of cetacean and seabird

activity is strongly linked to food availability and while minke whales and dolphins

have been noted feeding close inshore in the area, this normally occurs in late

summer / early autumn.

A surprising result is that only one group of bottlenose dolphins was sighted during

this survey. The Shannon estuary is home to Ireland’s only known resident group

Fig. 5. Survey effort and cetacean sightings recorded en route to survey location and on

site during leg 1.


of bottlenose dolphins. However IWDG sightings records 2 show few sightings of

bottlenose dolphins off Loop Head during May, with sightings peaking in mid to late

summer. The absence of bottlenose dolphins in the Shannon approaches during

this survey may be linked to:

1. Food availability: although there was a high degree of offshore feeding

activity among common dolphins, bottlenose dolphins were absent. It is

possible that the bottlenose dolphins remain inside the estuary to feed on

migrating salmon at this time of the year.

2. Factors related to the bottlenose dolphin calving period: calving in

bottlenose dolphins occurs at this time of the year and this may affect the

distribution of dolphins within and outside the estuary.

3. Bottlenose dolphin sensitivity to noise emissions from onboard

multi-beam and sub bottom profiler equipment: Although common

dolphins showed no severe reaction to the same equipment, different

dolphin species are sensitive to different sound frequency ranges. With

bottlenose dolphin sightings in the area being normally low at this time of

the year, there is little evidence to suggest that acoustic disturbance was a

significant factor.

The presence of basking sharks was noted only in sea state 0 - 1. The sightings

during this survey were preceded by a sighting of 100+ basking sharks off the west

Cork coast two week previously.

Surveyor: Dave Wall


3.1.2. Leg 2 – North Coast (3 June – 28 June 2004)


Sea state and visibility were favourable for much of leg 2. Sea state was recorded

at state 3 or less for 62% of the environmental stations. Precipitation occurred at

19.8% of the environmental stations but visibility was significantly restricted (<1km)

for just 3% of the survey period. Swell height was severe (2m+) at 27% of the

environmental stations (fig. 6).


192 hours of survey effort were recorded during leg 2 (fig. 7). Three species of

cetacean were recorded (table 2); Minke whale (Balaenoptera acutorostrata),

Bottlenosed dolphin (Tursiops truncatus) and Risso’s dolphin (Grampus griseus).

Two sightings of unidentified dolphin species were also made as were two

sightings of single basking sharks (figs. 8&9).

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Swell (1-3)

Wind Speed (Beaufort 1-10)

Fig. 6. Sea state, swell conditions and wind speed recorded twice daily during the survey.

Fig. 7. Survey effort at sea state = 3 recorded during Leg 2. Survey effort was recorded for 3 grid

squares (A–C).


Species Grid Cell


Bottlenose Dolphin (Tursiops truncatus) B 0.03

Minke Whale (Balaenoptera acutorostrata) B 0.01

Risso’s Dolphin (Grampus griseus) C 0.08

UnID Dolphin Species B 0.03

C 0.1

Table 2: Relative abundance of cetacean species in survey grid cells B & C.

Fig. 8: Survey effort and cetacean sightings recorded en route to survey

location and on site during leg 2.

Fig. 9: Survey effort and cetacean sightings recorded north of Malin Head

during leg 2.


3.1.2.3. Discussion

The low number of cetacean sightings was surprising given the high level of

cetacean activity in the south and south west at this time of the year. The IWDG

sightings database has a low number of sightings recorded from the north and

northwest of the country. Prior to these ShOp surveys it was thought that the low

number of sightings may have been related to low levels of survey effort but this

now has to be questioned.

This survey suggests that the relative abundance of cetaceans in this region is

much lower than other parts of the country at this time of year. At the time of the

survey numerous casual sightings had been reported around the country with most

cetacean activity been recorded in the south.

Another factor that could negatively influence sightings was the type of equipment

used on board during this survey. The multibeam (EM1002) used to map the sea

floor gives of frequencies of 93 and 98 kHz. The sonar (Simrad SP70) used has a

range between 20-30kHz and the bridge sounders give off frequencies of 50 and

200kHz. The wide range of high intensity acoustic frequencies produced may

have acted as a deterrent to cetaceans.

Most sightings of animals were at least 300m from the ship except for on the 26

June 2 sightings of basking sharks Cetorhinus maximus were made approximately

150m from the ship. On previous surveys where the same equipment was in use

cetaceans such as common dolphin Delphinus delphis, and pilot whales

Globicephala melanea have approached the vessel on numerous occasions and

did not exhibit any evident reaction to these high frequencies.

Surveyor: Joanne O’Brien


3.1.3. Leg 3 – Rockall Bank (2 July – 28 July 2004)


Weather conditions during the first half of leg 3 were good but sea conditions

deteriorated in the latter two weeks of the leg. Sea state was recorded at Beaufort

3 or less at 56.2% of the environment stations. Swell was light at 68.2% of the

environmental stations, moderate at 21.9% of stations and heavy at 9.9% of

stations. Visibility was good (>11km) at 90.6% of stations, moderate (1–10km) at

6.1% of stations and poor (<1km) at 2.8% of stations (fig. 10).


In all 91.9 hours of survey effort were recorded during this leg of the survey (fig.

11). Total survey effort in sea state 3 or less was 53.45 hours with the majority of

that effort concentrated over the southern Rockall Bank, Empress of Britain bank

and the south-western slopes of the Rockall bank. The level of cetacean activity

recorded during this survey was high with multiple sightings on days with good

survey conditions.

At least six species of cetacean were recorded (table 3); Atlantic white-sided

dolphin (Lagenorhynchus acutus), common dolphin (Delphis delphis), pilot whale

(Globicephala melas), harbour porpoise (Phocoena phocoena), minke whale

(Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus). A number of

sightings of unidentified dolphin species and small whale species were also made

(figs. 12&13).

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Vis (1-4)

Swell (1-3)

Wind Speed (knots)

Fig. 10. Sea state, visibility, swell conditions and wind speed recorded twice daily during the survey.


Species Grid Cell


Harbour Porpoise (Phocoena phocoena) B 0.1


Pilot Whale (Globicephala melas) B 0.6

White-sided Dolphin (Lagenorhynchus acutus) A 1.8

B 14.5


B 4.2

UnID Small Whale Species B 0.1


squares (A–F).

Table 3: Relative abundance of cetacean species in survey grid cells A & B. Cetaceans were recorded in

just two survey grid cells.

Fig. 12: Survey effort and cetacean sightings recorded en route to survey location and on site during leg 3.



Fourteen different bird species were recorded during this survey: Brown Guillemot

(UnCom); Fulmar (Com); Gannet (Occ); Great Skua (Occ); Kittiwake (Occ); Lesser

Black Back Gull (Occ); Manx Shearwater (Com); Pomarine Skua (UnCom); Puffin

(UnCom); Roseate Tern (UnCom), Sooty Shearwater (Co from mid month); Storm

Petrel (Com); Swallow (UnCom).

[Occ – Occassional; Com – Common; Com IS – Common Inshore; Sh – Ship Bound Birds; Sin – Single

sightings; UnCom – Uncommon; Num – Numerous; Com OS – Common Offshore].

3.1.3.4. Discussion

The number of cetaceans observed during the course of this survey was generally

high, though prevailing weather conditions in the latter half of leg 3 prevented

effective surveying from taking place. The most notable trend in the data was the

replacement of common dolphins (Delphinus delphis) by Atlantic white-sided

dolphins (Lagenorhynchus acutus) as the most common dolphin species over the

Rockall Bank. Common dolphins were also present on the Bank but their

occurrence was sporadic and in relatively low numbers.

Much of the survey took place close to the edge of the bank, where water depths

drop off to 1000m+. Despite this, the deep water cetacean species expected along

such a feature were notably absent. There were only three sightings of pilot whales

over the bank edge and no sperm whales or beaked whales. It may be that these

species favour deep water canyons such as found off the Hatton Bank to the

Fig. 13: Survey effort and cetacean sightings recorded over the Rockall Bank during leg 3.


northwest. Reports from an adjacent survey on the Hatton Bank indicated that pilot

whales, sperm whales and northern bottlenose whales were present in some

numbers (M. Mackey pers. comm.).

Many of the recorded sightings of unidentified dolphin species were thought to

have been of Atlantic white-sided dolphins. Other notable sightings were of

harbour porpoise, which occur in low numbers over offshore banks and of a fin

whale. The fin whale sighted was not feeding and three unidentified baleen whales

(thought to be of the same species) also seemed to be travelling rather than

feeding.

For much of the time the ships sonar was detecting groups of fish at depths of

around 90-100m (fig. 14). During daylight hours little fish activity was observed

above this depth, though three feeding frenzies (involving both cetaceans and

seabirds) were observed at the surface. At night, the fish species migrated higher

in the water column to depth of c50m (fig. 15). This abundance of potential food

species may account for the high relative abundance of Atlantic white-sided

dolphin over the Rockall Bank.

Surveyor: Dave Wall

Fig 14: Screen shots from depth sounder on board the R.V. Celtic Explorer showing fish/plankton marks during daytime at depths of c90m+

Fig 15: Screen shots from depth sounder on board the R.V. Celtic Explorer showing fish/plankton marks during night time at depths of c50m


3.1.4. Leg 4 – North Coast (30 July – 26 August 2004)


Weather conditions during the first half of leg 4 were good with a slight

deterioration of sea conditions during the latter half of the leg. Sea state was

recorded at Beaufort 3 or less at 66.2% of the environment stations. Swell was

light at 78.1% of the environmental stations, moderate at 15.4% of stations and

heavy at 6.5% of stations. Visibility was good (>11km) at 62.2% of stations,

moderate (1–10km) at 29.2% of stations and poor (<1km) at 8.6% of stations (fig.

16).


122.5 hours of survey effort were recorded during this leg (fig. 17), of this 64.4%

was conducted in conditions of sea state 3 or less.

The relative abundance of cetaceans in the area was very low with only 13

sightings, of three cetacean species, recorded during the 4 weeks of the survey

(table 4). The three cetacean species recorded were harbour porpoise (Phocoena

phocoena), minke whale (Balaenoptera acutorostrata) and Atlantic white-sided

dolphin (Lagenorhynchus acutus) (fig. 18)

All the sightings occurred less than 10km offshore in c30m of water with no

sightings occurring beyond 10km of the coast.

0

5

10

15

20

25

30

35

40

01/0

8/20

04am

01/0

8/20

04pm

03/0

8/20

04am

03/0

8/20

04pm

04/0

8/20

04am

04/0

8/20

04pm

05/0

8/20

04am

05/0

8/20

04pm

06/0

8/20

04am

06/0

8/20

04pm

07/0

8/20

04am

08/0

8/20

04am

09/0

8/20

04am

09/0

8/20

04pm

10/0

8/20

04am

10/0

8/20

04pm

11/0

8/20

04am

11/0

8/20

04pm

12/0

8/20

04am

12/0

8/20

04pm

13/0

8/20

04am

13/0

8/20

04pm

14/0

8/20

04am

16.0

8.20

04am

17.0

8.20

04am

17.0

8.20

04pm

18.0

8.20

04am

18.0

8.20

04pm

19.0

8.20

04am

19.0

8.20

04pm

20.0

8.20

04am

20.0

8.20

04pm

21.0

8.20

04am

21.0

8.20

04pm

22.0

8.20

04am

22.0

8.20

04pm

23.0

8.20

04am

23.0

8.20

04pm

24.0

8.20

04am

24.0

8.20

04pm

25.0

8.20

04am

Date/Time


Vis (1-4)

Swell (1-3)

Wind Speed (Knots)



Species Grid Cell


Harbour Porpoise (Phocoena phocoena) C 0.06


C 0.03

D 0.15

White-sided Dolphin (Lagenorhynchus acutus) B 0.55


B 0.94

UnID Cetacean Species C 0.03


squares (A–D).

Table 4: Relative abundance of cetacean species in survey grid cells A - D. Cetaceans were recorded in

all four survey grid cells.




There were many seabirds recorded during the survey with large numbers of

shags (Phalacrocorax aristotelis) in groups of close to 30 birds regularly recorded

near Tór Rocks and Inistrahull. Also regularly recorded from the observation deck,

in decreasing abundance, were gannet (Sula bassana), fulmar (Fulmarus

glacialis), lesser black-backed gull (Larus fuscus), kittiwake (Rissa tridactyla),

storm petrel (Hydrobates pelagicus), great black-backed gull (Larus marinus),

herring gull (Larus argentatus), manx shearwater (Puffinus puffinus), razorbill (Alca

torda), guillemot (Aria aalge), black guillemot (Cepphus grille), puffin (Fratercula

artica), great skua (Stercorarius skua), black-headed gull (Larus ridibundus), rock

dove (Columba livia), swallow (Hirundo rustica) and whimbrel (Numenius

phaeopus).

3.1.4.4. Discussion

The results of this survey corroborate results from prior surveys conducted off the

north-west coast in 2003 and 2004 15,16 which indicate that the ship-based and land

based survey work of the north Irish coastline needs to be conducted, to determine

cetacean relative abundance estimates for all months.

Surveyors: John Meade & Brendan Allen


3.1.5. Leg 5 – Cork/Kerry Coast (27 August – 23 September 2004)


Weather conditions during the first half of leg 5 were moderate with some good

survey conditions. Sea conditions deteriorated severely in the latter two weeks of

the leg and surveying was not possible from the 10.09.2004 onwards (with the

exception of the afternoon of 15.09.2004) as a series of Atlantic depressions and

gales swept the region.

Sea state was recorded at Beaufort 3 or less at only 33.3% of the environment

stations. Swell was light at 50% of the environmental stations, moderate at 13.9%

of stations and heavy at 36.1% of stations. Visibility was good (>11km) at 44.4% of

stations, moderate (1–10km) at 52.8% of stations and poor (<1km) at 2.8% of

stations (fig. 19).


Due to severe weather during the latter half of the leg, only 36.6 hours of survey

effort were recorded during this leg of the survey. Total survey effort in sea state 3

or less amounted to 19.5hrs for the leg (fig. 20). When weather conditions allowed,

the level of cetacean activity that was recorded during this leg (at sea state = 3)

was high.

The highest relative abundance of common dolphins recorded during any leg of

the survey was recorded during this leg, reaching a peak of 17.5 animals per hour

(table 5).

0

5

10

15

20

25

30

35

40

45

28.0

8.20

04am

28.0

8.20

04pm

29.0

8.20

04pm

30.0

8.20

04am

30.0

8.20

04pm

31.0

8.20

04am

31.0

8.20

04pm

01.0

9.20

04am

01.0

9.20

04pm

02.0

9.20

04am

02.0

9.20

04pm

03.0

9.20

04pm

04.0

9.20

04pm

05.0

9.20

04pm

06.0

9.20

04am

06.0

9.20

04pm

07.0

9.20

04am

07.0

9.20

04pm

08.0

9.20

04am

08.0

9.20

04pm

09.0

9.20

04am

09.0

9.20

04pm

10.0

9.20

04am

10.0

9.20

04pm

11.0

9.20

04pm

12.0

9.20

04pm

13.0

9.20

04pm

14.0

9.20

04pm

15.0

9.20

04am

15.0

9.20

04pm

16.0

9.20

04pm

17.0

9.20

04pm

18.0

9.20

04pm

19.0

9.20

04pm

20.0

9.20

04pm

21.0

9.20

04pm

Date


Vis (1-4)

Swell (1-3)

Wind Speed (knots)



Just two cetacean species were recorded during this leg, common dolphin

(Delphinus delphis) and minke whale (Balaenoptera acutorostrata) (fig. 21). A

number of unidentified cetacean sightings were recorded. One sighting of a

medium sized whale off Black Ball Head, Dursey Island was possibly of a

humpback whale. A group of small, fast moving dolphins sighted off Crow’s Head,

Dursey Island were thought to be striped dolphins. In both these cases species

identification could not be confirmed due to the adverse weather conditions.

In common with the survey during leg 1, most of the sightings of common dolphins

were made in deeper water more than 10-15km from the coastline.

Species Grid Cell


Common Dolphin (Delphinus delphis) B 17.5

Minke Whale (Balaenoptera acutorostrata) A 0.30


B 0.05

Fig. 20. Survey effort at sea state = 3 recorded during Leg 5. Survey effort was recorded for 2

grid squares (A & B).

Table 5: Relative abundance of cetacean species in survey grid cells A & B.



Fourteen different bird species were recorded during this survey: Brown Guillemot

(ComIS); Common Tern (Sin); Fulmar (Com); Gannet (Com); Greater Black

Backed Gull (UnCom); Great Skua (Occ); Herring Gull** (UnCom**); Kittiwake

(Com); Lesser Black Backed Gull (Com); Manx Shearwater (Com); Pomarine Skua

(Occ); Arctic Skua (Sin); Puffin (Sin); Racing Pigeon (Sin); Sooty Shearwater

(Occ); Storm Petrel (Com).

Key: [Occ – Occassional; Com – Common; Com IS – Common Inshore; Sh – Ship Bound Birds; Sin –

Single sightings; UnCom – Uncommon; Num – Numerous; Com OS – Common Offshore].

** Herring Gulls were almost completely absent during daylight hours, with only

one small flock of herring gulls seen resting on the foredeck on 10th September.

However in inshore waters large flocks of herring gulls (numbering in excess of

100-150 birds) were present each night, feeding on sprat and pipefish under the

ships lights.

3.1.5.4. Discussion

Despite the prolonged severe weather conditions during the latter two weeks of

this survey, data from sightings during the first two weeks show this to be an

important area for common dolphins. The relative abundance of common dolphins



recorded in the survey area was the highest recorded during any leg of the 2004

survey. Calves were recorded in many of the larger groups of common dolphins

sighted during the leg indicating that this may be an important breeding area for

this species.

The diversity of cetacean species recorded was low, however a number of

cetaceans were sighted but could not be identified due to poor visibility or rough

weather.

A number of non-cetacean species were sighted during this survey. On 30 August

a large leatherback turtle (Dermochelys coriacea) was sighted within 400m of the

ship, in deep water near to the shelf edge. The animal was actively swimming and

dived soon after being sighted.

On the 13 September a common seal was seen following the ship as it was hove-

to (making 1-2 knots into the weather) in rough seas. The seal followed in the

ships wake for around half an hour.

From the start of the survey a very large number of jellyfish were noted on the

surface. The jellyfish were of the species Vellella vellella or ‘by-the-wind sailor’.

This species floats on the surface with its tentacles hanging down below the water.

It ‘sails’ along in the wind using balloon-like membranes which project above the

water surface. Rafts of the jellyfish varied in density from a few per square meter to

solid rafts covering several square meters in area. The number of individuals must

have numbered many millions but could not be estimated as no boundary to the

rafts was reached. The jellyfish disappeared after easterly gales between the 7

and 9 September. No more were sighted after this time.

One night during the 3rd week of the survey bioluminescence (Notiluca sp.) was

noted in the ships bow waves.

Surveyor: Dave Wall


3.2. Cetacean Species Distribution and Relative Abundance

3.2.1. Survey Effort

Total effort for the survey, in all sea states amounted to 508hrs (fig. 22). Total survey

effort in sea state 3 or less amounted to 304.26hrs (fig. 23). During the survey a total

of 231 sightings of 2933 individuals and 8 cetacean species were recorded.

Fig. 22: Total survey effort (in all sea states) recorded during the survey.

Fig. 23: Survey effort recorded in sea state 3 or less during the survey.


3.2.2. Species Distribution and Relative Abundance.

3.2.2.1. Common Dolphin - Delphinus delphis.

Common dolphins occurred most frequently in waters over the Irish shelf. They

tended to occur in waters deeper than 30m with the majority of sightings being

made beyond 10km from the coastline (fig. 25).

In waters over the Irish shelf common dolphins were the most abundant cetacean

species, reaching a maximum relative abundance of 17.5aph off the west

Cork/Kerry coastline (fig. 26). 71 sightings of this species were made during the

survey.

Fig. 25: Distribution of Common Dolphin (Delphinus delphis) sightings recorded during all legs of the survey.

Fig. 24: Common Dolphin (Delphinus delphis)


The species is gregarious (1-60 animals, max. group size 300) and frequently

approached the survey vessel. For this reason it is thought that many repeat

sightings of the same groups were made while conducting transects within the

survey areas.

There was a marked reduction in the relative abundance of common dolphins in

offshore waters over the Rockall Bank. On the Rockall Bank Atlantic white-sided

dolphins replaced common dolphins as the most common cetacean species. In all

only 3 sightings of common dolphins were made over the Rockall Bank and their

incidence was too low to allow relative abundance estimates to be calculated.

Off the north and north-west coasts, no sightings of common dolphins were

confirmed during this survey. These results point to an extremely low relative

abundance of common dolphin in this region during the summer months. This is in

agreement with low relative abundances recorded during autumn/winter surveys

conducted in the same area by the IWDG in 2003/2004 15,16.

Only six sightings of common dolphin have been recorded off the Donegal coast

by the IWDG since 1996 and there is only one record from the Derry coast in 2002 2. A large number of sightings (500+) have been recorded off the west Cork and

Kerry coasts since 1994.

Fig. 26: Relative Abundance Map of Common Dolphin (Delphinus delphis) During Summer 2004.


The Cetacean Atlas of Europe (incorporating data from the JNCC, SeaWatch

Foundation & Sea Mammal Research Unit (SMRU) reports a very low relative

abundance of common dolphins in northern inshore waters. The atlas records a

high relative abundance of common dolphin off the west Cork, Clare and Kerry

coasts (data not analysed by season) 18. Coastal and Marine Resources Center

(CMRC) data also shows a high relative abundance of common dolphins off the

west Cork/Kerry coast during the summer (no summer data available for Shannon

approaches) 9.


3.2.2.2. Atlantic White-sided Dolphin - Lagenorhynchus acutus.

Atlantic white-sided dolphins had a northerly distribution. This species occurred

mainly in offshore waters over the Rockall bank, although two sightings were made

over or near the Irish shelf edge to the north-west of Ireland. 54 sightings of this

species were recorded in all (figs. 27&28).

Although gregarious, and sometimes noted for approaching vessels, in all cases

during this survey this species reacted negatively to the survey vessel. As these

animals were sighted in small to medium size groups (1-30 animals, max. group

size 60) it is possible that multiple sightings of the same animals occurred while

conducting transects over the Rockall Bank.

The majority of IWDG records of this species are offshore records from the north-

west coast 2. The JNCC Cetacean Atlas of Europe reports a high relative

abundance of Atlantic white-sided dolphins along the eastern margin of the Rockall

Bank 18. JNCC Atlas data also shows a high relative abundance of white-sided

dolphins over the Rockall bank (although survey effort was further north than

during the current survey) and along the shelf edge to the north-west of Ireland.

Fig. 27: Distribution of Atlantic white-sided dolphin (Lagenorhynchus acutus) sightings recorded during all legs of the survey.


CMRC records show a high relative abundance over the northern area of the

Rockall Bank during the summer. Unlike the current survey a low relative

abundance of white-sided dolphin was recorded over the southern bank, despite

high survey effort in this area.

Fig. 28: Relative abundance map of Atlantic white-sided dolphin (Lagenorhynchus acutus) during summer 2004.


3.2.2.3. Bottlenose Dolphin – Tursiops truncatus.

Only two sightings of bottlenose dolphins were recorded during the survey (max.

group size = 10). Although normally attracted to vessels, no animals approached

the survey ship during these two sightings. Most surprising was the almost

complete absence of bottlenose dolphins in the approaches to the Shannon

estuary (figs. 29&30). The Shannon estuary contains a breeding group of

bottlenose dolphins and has been designated a Special Area of Conservation

(SAC) for this species.

Most IWDG records (500+ records on file) of this species are from the south and

west coasts. Sightings are recorded predominantly in inshore coastal waters.

JNCC Atlas data shows a predominantly south-western distribution, with highest

relative abundances off the south-west Cork and Kerry coasts. CMRC data shows

sporadic sightings off bottlenose dolphin off the south and west coasts during

spring and summer, with sightings concentrated along the 200m and 500m shelf

contours.

Fig. 29: Distribution of Bottlenose dolphin (Tursiops truncatus) sightings recorded during all legs of the survey.


Fig. 30: Relative abundance map of Bottlenose dolphin (Tursiops truncatus) during summer 2004.


3.2.2.4. Harbour Porpoise – Phocoena phocoena.

Two sightings of harbour porpoise were recorded during the survey (max. group

size = 4). One sighting was in inshore waters off the Donegal coast. The second

sighting occurred in offshore waters over the Rockall Bank (figs. 31&32). The

majority of sightings of harbour porpoise in IWDG records occur in inshore waters,

with occasional sightings in deeper waters near the shelf edge. The occurrence of

porpoise in offshore waters over the Rockall Bank has been noted previously on

two occasions by Northridge et al. (1995) 8 and by Cronin & Mackey (2002) 19.

The majority of IWDG records (500+) of this species emanate from the south-west,

north-east and east coasts. Ireland has designated two special areas of

conservation for harbour porpoise, one in Roaringwater Bay, Co. Cork and the

second around the Blasket Islands, Co. Kerry.

The JNCC Atlas also shows a predominantly south-western, eastern and north-

eastern distribution for harbour porpoise around the Irish coast. Highest relative

abundances were recorded off the south-west and east coasts. CMRC data shows

highest relative abundances off the south-west and east coasts.

Fig. 31: Distribution of Harbour Porpoise (Phocoena phocoena) sightings recorded during all legs of the survey.


Fig. 32: Relative abundance map of Harbour Porpoise (Phocoena phocoena) during summer 2004.


3.2.2.5. Risso’s Dolphin – Grampus griseus.

Two sightings of Risso’s dolphins were made off the North coast (max. group size

= 2) (figs. 33&34). There are 15 sightings of this species on record in the IWDG

database from the Donegal Coast since 1995.

The majority of IWDG records (274) of this species come from the south and east

coasts. There are regular sightings recorded from the west and north coasts and

occasional sightings offshore.

JNCC Atlas data shows a mainly south-westerly and south-easterly distribution for

this species with highest relative abundance off the south-west coast. Additional

Records also show a high relative abundance along the shelf edge off the north-

west coast. CMRC data shows only occasional sightings of this species along the

shelf edge off the west coast and inshore off the NW and SW coasts.

Fig. 33: Distribution of Risso’s Dolphin (Grampus griseus) sightings recorded during all legs of the survey.


Fig. 34: Relative abundance map of Risso’s Dolphin (Grampus griseus) during summer 2004.


3.2.2.6. Pilot Whale – Globicephala melanea.

Five sightings of pilot whales were recorded (max. group size = 15). Two sightings

occurred along the shelf edge off the north-west coast and three over the Rockall

Bank (figs. 35&36). A CMRC survey being conducted at the same time over the

Hatton Bank (c100km further west) reported a higher incidence of pilot whales in

that area (M. Mackey pers. comm.). The deeper waters and bathymetric features

of the Hatton Bank may be a preferred habitat.

IWDG record for this species (83) show a mainly offshore distribution along the

shelf edge to the west and south-west. The highest incidence of inshore sightings

occurs off the south-west coast.

JNCC Atlas data shows an offshore distribution off the north-west and south-west

coasts. Highest relative abundances are recorded along the shelf edge, in the

Rockall Bank and over the Rockall and Hatton Banks. CMRC data also shows

highest relative abundances to occur along the western shelf edge (1000m+) and

over the Rockall and Hatton Banks.

Fig. 35: Distribution of Pilot Whale (Globicephala melanea) sightings recorded during all legs of the survey.


Fig. 36: Relative abundance map of Pilot Whale (Globicephala melanea) during summer 2004.


3.2.2.7. Minke Whale – Balaenoptera acutorostrata.

Eight sightings of this species were recorded during the survey (max. group size =

2). Most sightings were of single animals.

Distribution was predominantly in inshore waters over the Irish shelf but sightings

of this species were also recorded over the Rockall Bank (figs.38&39).

Fig. 38: Distribution of Minke Whale (Balaenoptera acutorostrata) sightings recorded during all legs of the survey.

Fig. 37: Minke Whale (Balaenoptera acutorostrata)


IWDG data shows a strongly inshore distribution for this species (500+ sightings).

The majority of records are from the southwest, north-west and north coasts. A

large number of sightings have also been recorded for the central Irish sea.

JNCC Atlas data shows a predominantly inshore distribution with highest relative

abundances off the south and west coasts. High relative abundances were also

recorded over the Rockall Bank. CMRC data recorded minke whales inshore off

the Kerry coast, over the shelf edge to the north-west and over the Rockall Bank

during the summer and over the Porcupine Bank during spring.

Fig. 39: Relative abundance map of Minke Whale (Balaenoptera acutorostrata) during summer 2004.


3.2.2.8. Fin Whale – Balaenoptera physalus.

A single sighting of this species was confirmed on the south-west margin of the

Rockall Bank.

A sighting of 2-3 unidentified large baleen whales which was recorded on the

eastern edge of the bank (fig. 41) was also thought to be of this species.

Fig. 41: Distribution of Fin Whale (Balaenoptera physalus) sightings recorded during all legs of the survey.

Fig. 40: Fin Whale (Balaenoptera physalus)


IWDG sightings data shows a mainly inshore distribution of fin whales along the

south coast during late summer and into winter. Additional sightings have been

recorded offshore in deep waters off the south-west and west coasts.

In addition to the seasonal occurrence off the south coast, the JNCC Atlas data

shows the highest relative abundance of this species in deep waters (beyond the

shelf edge) to the west of Ireland. CMRC data also shows this species occurring in

deep waters off the western shelf edge as well as in deeper waters to the west of

the Rockall Bank.


3.2.2.9. Unidentified Dolphin Species.

73 sightings of dolphins were made where species identification could not be

confirmed (fig. 42). Factors affecting ability to identify cetaceans include distance

of animal(s) from the survey platform, sea state, visibility and behaviour of the

animals involved.

Of the unidentified dolphin sightings on the Rockall Bank the vast majority were

thought to relate to Atlantic white-sided dolphins but were occasions where not

enough of the animals were seen to confirm id. In the same way, many of the

unidentified dolphin sightings off the west Cork/Kerry coast are thought to relate to

common dolphins.

Fig. 42: Sightings of unidentified dolphins recorded during all legs of the survey.


3.2.2.10. Unidentified Whale Species.

Ten whale (or cetacean) sightings were made where species could not be

confirmed (fig. 43). Of these one was of three large baleen whales (possibly fin

whales) over the Rockall Bank, two were of unidentified cetaceans (e.g. where

only a glimpse of a fin was seen) and six were of unidentified small whales.

Fig. 43: Sightings of unidentified whales recorded during all legs of the survey.


3.2.2.11. Basking Shark (Cetorhinus maximus).

Seven basking sharks were sighted during the survey (fig. 44). Three sightings

occurred west of Clare during May. All three sightings occurred in deeper water

(40-90m) and at least 10km from land. There may have been duplicate sightings of

the same species on successive days. Four basking sharks were sighted off the

north Donegal/Derry coast, two in June and two in August. All sightings were of

single animals.

Fig. 44: Sightings of Basking Shark (Cetorhinus maximus) recorded during all legs of the survey.


3.2.2.12. Other Species.

Common Seal (Phoca vitulina)

Two sightings of single common seals were recorded offshore. One was recorded

some 20km north-west of the Bloody Foreland, Co. Donegal in August. The

second was noticed following in the ship’s wake for some 20-30minutes 25km west

of Dursey Island in September.

Grey Seal (Halichoerus grypus)

A single grey seal was sighted in June 32km west of Loop Head.

Leatherback Turtle (Dermochelys coriacea)

A single leatherback turtle was sighted 60km west of Dursey Island during

September. The sighting coincided with a large influx of By-the-wind sailor jellyfish

(Vellella vellella) along the west and south coasts. The animal measured c2m in

length. IWDG data (16 sightings) shows a mainly south-western distribution for this

species.

Fig. 45: Sightings of Common Seal (Phoca vitulina), Grey Seal (Halichoerus grypus) and Leatherback Turtle (Dermochelys coriacea)

recorded during all legs of the survey.


4. Conclusions

Ships of Opportunity (ShOps) provide a useful, cost effective and practical method of

monitoring cetacean relative abundance and distribution. Due to the nature of the acoustic

mapping being conducted on board the R.V. Celtic Explorer during this survey, large amounts

of cetacean survey effort were focused in relatively small geographical areas. This resulted in a

trade off of larger survey area against obtaining a better picture of cetacean activity within the

areas surveyed.

The results of this survey show that cetacean relative abundance and species distribution can

vary significantly across even relatively short geographic distances. The major findings of this

survey were:

1. The most common cetacean species over the Irish shelf along the Clare and west

Cork/Kerry coasts was the common dolphin, reaching a peak relative abundance of

17.5aph off the Cork/Kerry coast. In both survey areas common dolphins were

primarily encountered in deeper waters (40m+) and more than 10km from the shore.

2. Atlantic white-sided dolphins were the most common cetacean species over the

southern end of the Rockall Bank, reaching a relative abundance of 14.5aph. The

relative abundance of common dolphins over the Rockall Bank was very low.

3. Despite the highest survey effort being focused on the north Donegal coast, cetacean

relative abundance in this region was very low. Similar results were noted during

surveys conducted by the IWDG in Autumn/Winter 2003/2004.

Surveys of distribution and relative abundance, conducted on board ships of opportunity,

provide the most cost effective and practical method of monitoring cetacean population in

Ireland’s offshore habitats. Survey effort to date has been focused on the summer months,

when weather is finest and many scientific and seismic surveys are conducted. It is evident

from inshore IWDG sightings data 2 that significant temporal variations in both the distribution

and relative abundance of many cetacean species occur.

More effort is required to survey more offshore marine habitats for cetacean distribution and

relative abundance. Year-round monitoring is all required in all areas to record seasonal trends

in cetacean distribution and relative abundance. As cetacean monitoring in offshore habitats is

both difficult and relatively expensive work, it is desirable that all distribution and relative

abundance data (collected during public or privately funded surveys in Irish waters) is made

available to researchers and conservation managers in a comparable format. This may take

the form of a central Irish database or through the publication of periodic joint reports involving

all groups conducting such research in Irish waters.


5. Acknowledgements

This project was sponsored by a grant under the Heritage Council Wildlife Grants scheme

(Grant No.13552). Thanks to the Geological Survey of Ireland for their cooperation and

support. Thanks to the Marine Institute for facilitating this survey and technical support. To the

captains, crews, party chiefs and fellow researchers of the R.V. Celtic Explorer for the help and

interest shown during these surveys. Finally to Fiona Fitzpatrick of the Marine Institute for her

support and organisational skills in facilitating and looking after both surveys and surveyors.


6. References

1. IWDG (2004). Online Cetacean Strandings Database. http://www.iwdg.ie/strandings/

2. IWDG (2004). Online Cetacean Sightings Database. http://www.iwdg.ie/iscope/

3. ARC (2004). Cetacean Monitoring in North-west European Waters. ARC Report No. 1

4. Evans, P.G.H. (1981) NE Atlantic summer 1980 whale & seabird cruise. Mammal

Society. London.

5. Hammond, P.S., Benke, H., Berggren, P., Borchers, D.L., Buckland, S.T., Collet, A.,

Heide-Jørgensen, M.P., Heimlich-Boran, S., Hiby, A.R., Leopold, M.F. and Øien , N.

(1995). Distribution and abundance of the Harbour porpoise and other small cetaceans in

the North sea and adjacent waters. LIFE 92-2/UK/027.

6. Ingram, S. Englund, A. and Rogan, E. (2001). An extensive survey of bottlenose

dolphins (Tursiops truncatus) on the west coast of Ireland. Report to the Heritage Council,

WLD/2001/42.

7. Leopold, M.F., Wolf, P.A. and Van de Meer, J. (1992). The elusive harbour porpoise

exposed: strip transect counts off southwestern Ireland. Netherlands Journal of Sea

Research 29, pp. 395-402.

8. Northridge, S., Tasker, M.L., Webb, A. and Williams, J.M. (1995). Distribution and

relative abundance of harbour porpoises (Phocoena phocoena L.), white-beaked dolphins

(Lagenorhynchus albirostris Gray), and minke whale (Balaenoptera acutorostrata

Lacepède) around the British Isles. ICES Journal of Marine Science 52, pp. 55-66.

9. Ó Cadhla, O., Mackey, M., Aguilar de Soto, N., Rogan, E. & Connolly, N. (2004).

Cetaceans and Seabirds of Ireland’s Atlantic Margin. Volume II – Cetacean distribution and

abundance. Report on research carried out under the Irish Infrastructure Programme

(PIP): Rockall Studies Group (RSG) projects 98/6 and 00/13, Porcupine Studies Group

project P00/15 and Offshore Support Group (OSG) project 99/38. 89pp.

10. Pollock, C., Reid, J.B., Webb, A. and Tasker, M.L. (1997). The distribution of seabirds

and cetaceans in the waters around Ireland. JNCC Report, No. 267.

11. Gordon, J., Berrow, S.D., Rogan, E. & Fennelly, S. (1999). Acoustic and visual survey

of cetaceans off the Mullet peninsula, Co. Mayo. Irish Naturalist Journal, 26, 251-259.

http://www.iwdg.ie/strandings/

http://www.iwdg.ie/iscope/


12. R.A. Charif & C.W. Clark (2000). Acoustic monitoring of large whales off north and west

Britain and Ireland: a two year study, October 1996 – September 1998. JNCC Report 313.

13. Chariff, R.A., Clapham, P.J. & Clark, C.W. (2001). Accoustic detection of singing

humpback whales in deep waters off the British Isles. Mar. Mamm. Sci., 17(4), 751-768.

14. Aguilar de Soto, N., Rogan, E., Ó Cadhla, O., Gordon, J.C.D., Mackey, M. &

Connolloy, N. (2004). Cetaceans and Seabirds of Ireland’s Atlantic Margin. Volume III –

Acoustic Surveys for Cetaceans. Report on research carried out under the Irish

Infrastructure Programme (PIP): Rockall Studies Group (RSG) projects 98/6 and 00/13,

Porcupine Studies Group project P00/15 and Offshore Support Group (OSG) project 99/38.

51pp.

15. IWDG (2003). Cetacean Distribution & Relative Abundance Survey during Ground fish

Survey 2003. http://www.iwdg.ie/downloads/CelticExplorerReport2003.PDF

16. IWDG (2004). Cetacean Distribution and Relative Abundance Survey during Herring

Acoustic Survey 2004. http://www.iwdg.ie/downloads/CelticExplorerReport2004.PDF

17. IWDG (2004). Cetacean Distribution and Relative Abundance Survey during Blue Whiting

Survey 2004. http://www.iwdg.ie/downloads/CelticExplorerReport2004b.PDF

18. Reid, J.B., Evans, P.G.H. & Northridge, S.P. (2003) Atlas of Cetacean Distribution in

north-west European Waters. Joint Nature Conservation Committee, Peterborough.

19. Cronin, M. & Mackey, M. (2002). Cetaceans and seabirds in waters over the Hatton-

Rockall region. Cruise report to the GSI: http://www.gsiseabed.ie/petrov02report.pdf

20. Government of Ireland (1976). Wildlife Act, 1976. Government Publications Office,

Molesworth St., Dublin 2.

21. Government of Ireland (2000). Wildlife (Amendment) Bill, 1999. Government Publications

Office, Molesworth St.

22. European Commission (1992). Council directive on the conservation of natural habitats

and of wild fauna and flora. Council Directive 92/43/EEC

23. IFAW (2000). IFAW automatic data logging program: Logger 2000.

http://www.ifaw.org/ifaw/general/default.aspx?oid=25653

http://www.iwdg.ie/downloads/CelticExplorerReport2003.PDF

http://www.iwdg.ie/downloads/CelticExplorerReport2004.PDF

http://www.iwdg.ie/downloads/CelticExplorerReport2004b.PDF

http://www.gsiseabed.ie/petrov02report.pdf

http://www.ifaw.org/ifaw/general/default.aspx?oid=25653


Appendix I: List of cetacean species recorded in Irish waters. Atlantic White-Sided Dolphin Lagenorhynchus actus co / os / br

Beluga Delphinapterus leucas va / arc /

Blue Whale Balaenoptera musculus uc / os / se

Bottlenose Dolphin Tursiops truncatus co / br

Common Dolphin Delphis delphis co / br

Cuvier's Beaked Whale Ziphius cavirostris uc / os

False Killer Whale Pseudorca crassidens uc / os

Fin Whale Balaenoptera physalus co / se

Gervais’ Beaked Whale Mesplodon europaeus va / st

Harbour Porpoise Phocoena phocoena co / is / br

Humpback Whale Megaptera novaeangliae ra / se

Killer Whale Orcinus orca sp / br?

Minke Whale Balaenoptera acutorostrata co / br?

Northern Bottlenose Whale Hyperoodon ampullatus uc / os

Northern Right Whale Eubalaena glacialis va / os

Pilot Whale (long-finned) Globicephala melas co / os / br

Pygmy Sperm Whale Kogia breviceps uc / os

Risso's Dolphin Grampus griseus co / br

Sei Whale Balaenoptera borealis uc

Sowerby's Beaked Whale Mesplodon bidens uc / os

Sperm Whale Physeter macrocephalus co / os / br?

Striped Dolphin Stenella coeruleoalba uc / os

True's Beaked Whale Mesplodon mirus uc / os

White-Beaked Dolphin Lagenorhynchus albirostris uc / os

co – common; os – offshore species; br – breeds in Irish waters; va – vagrant; arc – arctic species; uc – uncommon; se – seasonal; st – known only from strandings; is – inshore species; sp – sporadic.


Appendix II: Daily Wind Speed and Directions Recorded During Each Leg of the Survey

Leg 1: Wind direction recorded twice daily during the survey.

Date Time Wind Dir. 21.05.2004 am W pm W 22.05.2004 am W pm W 23.05.2004 am S pm S 24.05.2004 am NW pm W 25.05.2004 am NW pm W 26.05.2004 am NE pm W 27.05.2004 am N pm NE 28.05.2004 am E pm E 30.05.2004 am SE pm E 31.05.2004 am N pm S 01.05.2004 am SW pm SW


Date Time Wind Dir.

04.06.2004 pm SW

05.06.2004 am W

pm W

06.06.2004 am NW

pm NW

07.06.2004 am NW

pm NW

08.06.2004 am W

pm W

09.06.2004 am W

pm W

10.06.2004 am SW

pm SW

11.06.2004 am W

pm W

12.06.2004 am W

pm W

13.06.2004 am W

pm W

14.06.2004 am W

pm W

15.06.2004 am NW

pm W

16.06.2004 am W

pm NW

17.06.2004 am W

pm W


18.06.2004 am NW

pm N

19.06.2004 am NW

pm NW

20.06.2004 am N

pm NW

21.06.2004 am N

pm N

22.06.2004 am E

pm E

24.06.2004 am NW

pm NW

25.06.2004 am NW

pm NW

26.06.2004 am SE

pm SE

27.06.2004 am SW

pm SW

28.06.2004 am SW

pm SW

29.06.2004 am S

pm S


Date Time Wind Dir.

03.07.2004 am W

pm NW

04.07.2004 am NW

pm SW

05.07.2004 am SW

pm SW

06.07.2004 am E

pm NE

07.07.2004 am NE

pm N

08.07.2004 am W

pm NW

09.07.2004 am NW

pm NW

10.07.2004 am W

pm SW

11.07.2004 am W

pm W

12.07.2004 am E

pm SE

13.07.2004 am S

pm SW

14.07.2004 am NW

pm SW

15.07.2004 am SW

pm SW

16.07.2004 am SW


pm SW

18.07.2004 am W

pm W

19.07.2004 am S

pm SE

21.07.2004 am NW

pm SW

22.07.2004 am SW

pm SW

25.07.2004 am W

pm W

26.07.2004 am SW

pm SW

27.07.2004 am NE

pm E


Date Time Wind Dir.

01.08.2004 am SE

pm S

03.08.2004 am NW

pm NW

04.08.2004 am NW

pm SE

05.08.2004 am E

pm E

06.08.2004 am SW

pm W

07.08.2004 am E

08.08.2004 am E

09.08.2004 am SE

pm SE

10.08.2004 am E

pm N

11.08.2004 am E

pm E

12.08.2004 am E

pm NE

13.08.2004 am E

pm NE

14.08.2004 am E

16.08.2004 am SW

17.08.2004 am SE

pm SE

18.08.2004 am N

pm N

19.08.2004 am N

pm N

20.08.2004 am N

pm NW

21.08.2004 am NW

pm SE

22.08.2004 am SE


pm E

23.08.2004 am E

pm E

24.08.2004 am E

pm N

25.08.2004 am NW


Date Time Wind Dir.

28.08.2004 am W

pm SW

29.08.2004 pm W

30.08.2004 am N

pm N

31.08.2004 am SE

pm S

01.09.2004 am S

pm NE

02.09.2004 am SW

pm SW

03.09.2004 pm SW

04.09.2004 pm S

05.09.2004 pm W

06.09.2004 am N

pm NW

07.09.2004 am E

pm SE

08.09.2004 am NE

pm SE

09.09.2004 am E

pm SE

10.09.2004 am SE

pm S

11.09.2004 pm W

12.09.2004 pm S

13.09.2004 pm SW

14.09.2004 pm NW

15.09.2004 am S

pm S

16.09.2004 pm S

17.09.2004 pm SW

18.09.2004 pm W

19.09.2004 pm SW

20.09.2004 pm W

21.09.2004 pm W

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