1

An investigation into the effects of boat proximity on the behaviour of bottlenose

dolphins (Tursiops truncatus) in Cardigan Bay.

Independent Studies for Biological and Forensic Sciences

6BY995

BSc Honours in Zoology

C300

April 2015

Sinead Martin

Biological and Forensic Sciences, University of Derby, Kedleston Road, Derby,

Derbyshire, DE221GB, UK

2

Abstract

A constant challenge in marine conservation science is understanding how human activities impact marine

species. For bottlenose dolphins, Tursiops truncatus, a frequent anthropogenic threat can occur through

interactions with marine vessels. Boats commonly disrupt dolphin feeding, mating, and resting behaviours;

that ultimately can lead to permanent changes in dolphin demography and habitat-usage. However, some

dolphin populations become habituated and show no behavioural responses to boats. In Cardigan Bay,

Wales, dolphins routinely interact with a variety of marine vessels. However, there is debate among local

organisations about whether boat activities in the bay are negatively impacting the dolphins. The goal of

this study was to determine whether boats influence the behaviour of dolphins in Cardigan Bay. Land based

surveys were conducted during May and June in 2015 to quantify the frequency of dolphin behaviours in

relation to boats. These data were combined with similar surveys conducted in 2005 and 2010 to

determine if dolphins demonstrate positive or negative reactions to boats; whether, the variety of dolphin

behaviours decreased when boats were present; and, whether boat traffic and dolphin abundance has

changed since 2005. Overall, dolphins in Cardigan Bay did not appear to be affected by boat activity. An

increase in dolphin sightings between 2005 and 2015 appeared to be independent of boat activity that did

not show any predictable change during the same period. Further, the majority of dolphin responses to

boats were neutral; and very few dolphins altered their behaviour before and during boat encounters.

However, not all interactions were benign: motorboats and vessels operated in a negative manner elicited

negative behaviour from dolphins. Hence, while dolphins in Cardigan Bay appear to be a strong population

that are accustomed to boat activities, a small number of boats are a potential threat. Future research and

management strategies may look to these specific dolphin-boat interactions to enhance the protection of

the dolphins.

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Index of Tables and Figures

Figure 1: Three bottlenose dolphins, Tursiops truncatus, in Cardigan Bay West Wales. (Perry 2016)……………8

Figure 2: A bottlenose dolphin, Tursiops truncatus, exhibiting bow riding behaviour during a boat encounter

with a SCY boat, any boat under a sail (Perry 2016)………………………………………………………………………………………9

Figure 3: Map of the study site off the coast of Wales, United Kingdom. (a) Cardigan Bay with the Special

Area of Conservation (boxed area). (b) New Quay Bay, showing the location from where observations were

made and the survey area (boxed area)……………………………………………………………………………………………………..13

Figure 4: Summary of all observed dolphin-vessel interactions grouped by vessel behaviours (top panel,

positive vessels; bottom panel, negative vessels) and bottlenose dolphin (Tursiops truncatus) behavioural

responses (positive, neutral and negative) in Cardigan Bay, Wales, from 2005, 2010 and 2015. Each bar

represents to the total count of observed dolphin behaviour with the overall number of observations

totalling 590……………………………………………………………………………………………………………………………………………….20

Figure 5: Summary of observed dolphin-vessel interactions grouped by vessel behaviours (top panel,

positive vessels; bottom panel, negative vessels) and dolphin (Tursiops truncatus) behavioural responses

(positive, neutral and negative) in Cardigan Bay, Wales, from 2015. Each bar represents to the total count

of observed dolphin behaviour…………………………………………………………………………………………………………………..22

Figure 6: The effects of boat type on the proportion of positive bottlenose dolphin (Tursiops truncatus)

responses in Cardigan Bay, Wales. X-axis labels for boat type are abbreviated: MB = motor boat, Other = all

other boat types, SCY = sail boats, VPB = visitor passenger boat, CF = commercial fishing boat, and SB =

speed boat………………………………………………………………………………………………………………………………………………….24

Figure 7: The effects of the presence or absence of boats on the frequency of behavioural responses for

bottlenose dolphins (Tursiops truncatus) in Cardigan Bay, Wales. X-axis shows abbreviations for the dolphin

activity states: S2, staying with slow circling and milling; S3, staying with long dives and foraging; S6, staying

with fast circling; T1, travelling with regular surfacing; T2, travelling with long dives and irregular surfacing;

Other, all other behaviours…………………………………………………………………………………………………………………………26

Figure 8: Graphical representation of dolphin activity states prior to and during an encounter with a boat in

Cardigan Bay, Wales, in 2015. Activity states on the x-axis abbreviated: S1, motionless lying; S2, staying with

slow circling and milling; S3, staying with long dives and foraging; S4, chasing prey on surface; S6, staying

with fast circling; T1, travelling with regular surfacing; T2, travelling with long dives and irregular surfacing;

T3, rapid travel; TS tail slapping With prior referring to before the vessel encounter and the during bar

referring to the behaviour during the vessel encounter……………………………………………………………………………..29

Table 1: List of the categories of boats and their abbreviation observed in the surveys of Cardigan Bay,

Wales………………………………………………………………………………………………………………………………………………………….15

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Table 2: List of the manner in which boats were observed to be operated in surveys from Cardigan Bay,

Wales. Specific boat behaviours are abbreviated to codes with the full description of the behaviour in the

adjacent cell. General boat behaviours are indicated with colour over the specific behaviour code. Green

and red indicate positive and negative behaviours, respectively, in accordance with the Ceredigion

Recreational Boat Users Code of Conduct (Ceredigion District Council, 2010)…………………………………………….15

Table 3: List of bottlenose dolphin (Tursiops truncatus) behaviours observed in surveys of Cardigan Bay,

Wales. Specific dolphin behaviours are abbreviated to codes with the full description of the behaviour in

the adjacent cell. General dolphin behaviours are indicated with colour over the specific behaviour code.

Green, yellow, and red indicate positive, neutral, and negative behaviours, respectively…………………………..16

Table 4: Summary statistics for the number and percentage of bottlenose dolphin sightings recorded

between 2005 and 2015 in Cardigan Bay, Wales. (a) Count and percentage data presented as summaries for

sightings of bottlenose dolphins and non-bottlenose dolphins. BND = bottlenose dolphins. (b) Summary

statistics for the frequency analysis testing the effects of year on bottlenose dolphin sightings…………………19

Table 5: Summary statistics for the frequency analysis testing the effects of vessel behaviour (two levels:

positive and negative) on dolphin (Tursiops truncatus) behaviour (three responses: positive, neutral and

negative) in Cardigan Bay, Wales in 2005, 2010, and 2015…………………………………………………………………………21

Table 6: Summary statistics for frequency analysis testing the effects of vessel behaviour (two levels:

positive and negative) on dolphin (Tursiops truncatus) behaviour (three responses: positive, neutral and

negative) in Cardigan Bay, Wales in 2015. (a) Result of the full frequency analysis with all levels of boat and

dolphin behaviour. (b) Results of the pooled frequency analysis with positive and neutral dolphin

behaviours pooled………………………………………………………………………………………………………………………………………23

Table 7: Summary statistics for frequency analysis testing the effects of the presence of absence of boats

on the variety of dolphin (Tursiops truncatus) behaviours in Cardigan Bay, Wales in 2015. (a) All years, (b)

2005, (c) 2010, (d) 2015…………………………………………………………………………………………………………………………….27

Table 8: Summary statistics for pairwise z-test analysis testing whether dolphins changed activity state prior

to and during an encounter with a boat in Cardigan Bay, Wales in 2015. Only the five most common dolphin

activity states were tested. Activity states abbreviated: S2, staying with slow circling and milling; S3, staying

with long dives and foraging; S6, staying with fast circling; T1, travelling with regular surfacing; T2, travelling

with long dives and irregular surfacing……………………………………………………………………………………………………….28

Table 9: Summary data for the number and percentage of times boats were present of absent during

surveys of the in Cardigan Bay, Wales, in 2005, 2010, and 2015…………………………………………………………………30

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Table 10: Summary statistics for frequency analysis testing the effects of year (three levels: 2005, 2010, and

2015) on the presence of absence of boats in Cardigan Bay, Wales……………………………………………………………30

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Acknowledgements

Many thanks to Sarah Perry for all her support during this study, photographs for illustrating this study and

allowing access to historical data for comparison. I would also like to thank the volunteers of the Cardigan

Bay Marine Wildlife Centre both past and present for all their time and hard work. I would also like to thank

my independent study supervisor Dr Nell Beaumont for all her advice and support on the concept of the

project and the analysis of the data.

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Table of Contents

Abstract............................................................................................................................................................ 2

Index of Tables and Figures...............................................................................................................................3

Acknowledgements...........................................................................................................................................6

1.0 Introduction……………………………………………………………………………………………….……………………..……………………8

1.1 Short Term Negative Reactions to Vessels…………………….………………………………………………..……………………..9

1.2 Long Term Negative Reactions to Vessels…………………….………………………………………………………………………10

1.3 Neutral and Positive Reactions to Vessels………………………………................................................................10

1.4 Vessel Interaction in Cardigan Bay………………………………………………………………………………………………………..11

1.5 Aims and Objectives………….………………………………………………………………………………………………………………….12

2.0 Methodology.............................................................................................................................................12

2.1 Study Species and Study Sites………….........................................................................................................12

2.2 Surveys and Data Collection for 2015……..................................................................................................14

2.3 Surveys and Data Collection for 2005 and 2015……………………………………………………………………………………16

2.4 Data Analysis………………………………………………............................................................................................17

3.0 Results……………………………………................................................................................................................ 18

3.1 Observations and Sightings……………………................................................................................................. 18

3.2 Hypothesis One…………………………………………………………………………………………………………………………….........19

3.3 Dolphin Reactions to Specific Vessels……………………………………………………………………………………………………23

3.4 Hypothesis One with Visitor Passenger Boat Type Removed…………………………………………………………………23

3.5 Hypothesis Two……….................................................................................................................................25

3.6 Hypothesis Three………………………..............................................................................................................30

4.0 Discussion..................................................................................................................................................31

4.1 Dolphin Abundance………………………………………………………………………………………………………………………………31

4.2 Dolphin Reactions to Vessel Encounters....................................................................................................32

4.3 Dolphin Reactions to Specific Vessel Types...............................................................................................32

4.4 Dolphin Behaviour Dependent on and Independent of Vessel Interactions.............................................33

4.5 Potential Consequences of Continued Vessel Interaction.........................................................................34

4.6 Future Research.........................................................................................................................................34

5.0 Conclusion…………………………………………......................................................................................................35

6.0 References.................................................................................................................................................36

7.0 Appendix One Marine Code of Conduct.................................................................................................40

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1.0 Introduction

An enduring challenge in marine conservation science is understanding the impacts of human activities on

marine mammals. For species with populations in cosmopolitan coastal areas, such as the bottlenose

dolphin Tursiops truncatus, (Figure 1) contact with humans can be common but potentially detrimental to

the health and survival of the dolphins (Constantine et al., 2004). One of the most frequent anthropogenic

threats to dolphins can occur through interactions with marine vessels (Figure 2) (Nowacek et al., 2001;

Pierpoint et al., 2009).

Figure 1: Three bottlenose dolphins, Tursiops truncatus, in Cardigan Bay West Wales. (Perry 2016)

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Figure 2: A bottlenose dolphin, Tursiops truncatus, exhibiting bow riding behaviour during a boat encounter

with a SCY boat, any boat under a sail (Perry 2016).

1.1 Short Term Negative Reactions to Vessels

Many studies conducted throughout the world have demonstrated that dolphin populations are negatively

affected by boat activity (e.g., Wilson et al., 1997; Constantine et al., 2004; Ribeiro et al., 2005; Arcangeli &

Crosti, 2009; Christiansen et al., 2010; Papale et al., 2011). The most evident and damaging threat to

dolphins occurs when there are direct collisions with boats that can result in severe injury or mortality

(Stone & Yoshinaga, 2000). However, the majority of dolphin-boat encounters are nonlethal, because

dolphins often demonstrate behaviours to avoid boats and these behaviours may allow dolphins to inhabit

areas of high boat activity (Nowacek et al., 2001; Lusseau, 2003; Neumann & Orams, 2006; Pierpoint et al.,

2009). Whilst collisions with boats are easily observed and quantified, avoidance behaviours are less readily

quantified and less well understood (Hastie et al., 2003, Lusseau, 2003). Hence, for most dolphin

populations there is little understanding of whether dolphins are impacted by boats and if dolphins use

particular behaviours to cope with the potential threat.

Among worldwide populations, bottlenose dolphins demonstrate behavioural changes in response to boat

activity. For example, bottlenose dolphins off the coast of Tanzania are less likely to feed, rest or socialise in

the presence of marine vessels than when vessels are absent (Christiansen et al., 2010). Similar results have

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been reported in bottlenose dolphin populations in New Zealand (Constantine et al., 2004), Australia

(Arcangeli & Crosti, 2009) and Italy (Papale et al., 2011). Other observed behavioural responses to boats

include changes in breathing and phonation rates (Arcangeli & Crosti, 2009), the degree of synchronous

interactions among dolphins in a social group (Hastie et al., 2003), the length of dive periods (Lusseau,

2003) and the direction and speed of swimming (Nowacek et al., 2001). All of these changes in behaviour

can result in negative consequences for dolphins. For example, avoidance behaviours can be energetically

costly and this effect may be exacerbated because any time spent avoiding boats implicitly decreases the

amount of time dolphins can dedicate to feeding or resting (Christiansen et al., 2010). Further, dolphins

communicate by sound and depend on echolocation to forage and navigate the environment, but noise

from boat engines can disrupt communication and feeding efficiency (Hastie et al., 2003).

1.2 Long Term Negative Responses to Vessels

Over longer time scales, repeated exposure to boat activity can lead to permanent behavioural changes

(Nowacek et al., 2001), and long-term changes in behaviour have the potential to indirectly cause

populations to decline (Lusseau, 2005). For example, boat activity can cause dolphins to avoid their

preferred habitats (Lusseau, 2005, La Manna et al., 2014). In the short-term, dolphins typically return to

these disturbed areas, but cumulative encounters with multiple boats over longer periods can cause

dolphins to vacate an area permanently (Lusseau, 2005). At the population level, the exclusion of dolphins

from any given area may lead to a decline in the total amount of habitat available for foraging, which in

turn puts pressure on the carrying capacity of the remaining habitat, increases intraspecific competition for

food and ultimately could lead dolphin populations to decline (Lusseau, 2005).

1.3 Neutral and Positive Reactions to Vessels

While the negative impacts of boats on dolphins are well documented, they are not ubiquitous as neutral

and positive interactions are also observed in some locations. For example, numerous studies report the

majority of dolphin-boat encounters elicit no discernible response from dolphins (e.g., Gregory & Rowden,

2001; Papale et al., 2011; Constantine et al., 2004; Hastie et al., 2003). Many authors hypothesise neutral

responses are evidence that dolphins become habituated to the presence of boats and no longer perceive

them as a threat (Gregory & Rowden, 2001; Constantine et al., 2004; Sini et al., 2005). Observations of

positive dolphin interactions include surfing, bow riding, and breaching in the waves and turbulence

created by boat movements (Wursig & Wursig, 1979; Gregory & Rowden, 2001; Sini et al., 2005). Further,

research conducted in Aberdeen Harbour, Scotland, found dolphins also opportunistically feed on fish

startled by boat propellers (Sini et al., 2005).

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Importantly, dolphin-boat interactions are often more complicated than simple negative or positive

observations, as other studies have shown dolphin responses depend on the type and size of boat involved

in an interaction (Sini et al., 2005) and the sex of the dolphin (Lusseau, 2003). For example, within a

population of dolphins in Italy, Papale et al (2011) observed dolphin encounters with sail boats were

exclusively neutral, compared to positive and negative interactions with fishing and high-speed vessels,

respectively. In contrast, other studies have found seemingly benign watercrafts, such as kayaks, elicit the

most pronounced behavioural changes in dolphins that result in a startle response more commonly seen in

predator-prey interactions (Gregory & Rowden, 2001). Further, Sini et al (2005) reported dolphins appeared

to become habituated to boats when boat traffic moved at consistent speeds and followed similar routes;

but when boats deviated from the normal route or showed variable speeds, dolphins exhibited more

negative responses. From a conservation perspective, dolphin-boat interactions can indirectly benefit

dolphins through the consequences of ecotourism, because dolphin-watching from tourism vessels has

been shown to enhance awareness of conservation issues affecting the marine environment among

laypeople (Orams, 1997). Ecotourism also provides local economies with alternatives to traditional

businesses that can be detrimental to marine mammals (e.g., whaling and fishing) (Duffus & Dearden,

1993). However these benefits are balanced against the negative impacts of boat-based ecotourism on

dolphin behaviour (Constantine et al., 2004; Christiansen et al., 2010).

Overall, evidence suggests boating activities negatively affect dolphins. However, these effects are variable,

and instead, the outcomes of dolphin-boat interactions depend on numerous factors that vary within and

among locations and dolphin populations. Hence, in order to manage any given population of dolphins, it is

crucial that the impacts of dolphin-boat interactions are accurately quantified.

1.4 Vessel Interaction in Cardigan Bay

In Cardigan Bay on the western coast of Wales, humans and dolphins routinely interact (Gregory &

Rowden, 2001). But there is considerable debate among local organisations about whether these

interactions are negatively impacting the dolphin population. Early studies of dolphins in the region

identified a substantial but potentially vulnerable population (Mayer et al., 1991). In 1994 the first dolphin

monitoring programs were initiated (Pierpoint et al., 2009). Since monitoring began, various actions have

been invoked by government agencies to help protect the dolphins in the bay (Pierpoint et al., 2009): a

code of conduct for boat activity was implemented by the local government, Ceredigion District Council,

(Appendix One); and, the area became a Special Area of Conservation in 2004 (European Union ‘Habitats

Directive’). These measures appear to have benefited the dolphins: surveys conducted between 1995-2007

indicate the overall population of dolphins in Cardigan Bay has increased (Pierpoint et al., 2009). However,

dolphin abundance in some areas within the bay declined, which may have been related to boat activity

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(Pierpoint et al., 2009). In contrast to the correlative approach of the long-term surveys, Gregory & Rowden

(2001) conducted research in Cardigan Bay focusing explicitly on dolphin-boat interactions and concluded

boats were of little concern to the local dolphin population. Approximately, 62% of dolphins showed no

visible behavioural changes in directional movement in the presence of boats (Gregory & Rowden, 2001).

These findings are supported by data collected over 20 years by the Cardigan Bay Marine Wildlife Centre

(Perry, 2016). However, the Sea Watch Foundation, an environmental protection group, claim the

bottlenose dolphins in Cardigan Bay are being notably affected and driven away by increased boat traffic

(Feingold and Evans, 2013). Overall, evidence of boats negatively impacting dolphins in Cardigan Bay is

inconclusive. Hence, there is a need for a current scientific assessment of dolphin-boat interactions in

Cardigan Bay to reconcile apparent discrepancies amongst past studies (Pierpoint et al., 2009).

1.5 Aims and Objectives

The overall goal of this study was to determine the impact of boat activity on bottlenose dolphins in

Cardigan Bay. The primary focus was on the short-term impact of boats on dolphins, and this was

addressed with two questions. Firstly, do the dolphins in Cardigan Bay demonstrate positive or negative

reactions to boat encounters? Secondly, does the variety of dolphin behaviours decrease when boats are

present? A secondary aim of the study was to investigate long-term associations between dolphins and

boats. Hence, a third question addressed whether there has been an increase of traffic since 2005, and was

this related to dolphin abundance? Collectively, these questions will give crucial information about the

current impacts of dolphin-boat interactions in Cardigan Bay.

2.0 Methods

2.1 Study species and Study site

Tursiops truncatus is a species of bottlenose dolphins found in tropical to temperate regions throughout

the world’s oceans and has been the focus of many studies investigating dolphin-boat interactions

(example: Constantine, Brunton & Dennis, 2004; Arcangeli & Crosti, 2009; Christiansen et al., 2010; Papale,

Azzolin & Giacoma, 2011; Prideaux, 2012). Locally, a population of bottlenose dolphins inhabits Cardigan

Bay on the western coast of Wales, and while some individuals of this population have been reported in

other locations, most individuals exhibit high site fidelity and are considered residents of the bay (Gregory

& Rowden, 2001; Feingold & Evans 2013). Cardigan Bay is a shallow bay (depth < 50 m) and covers an area

of approximately 5500 km2 (Figure 1a). Due to the resident population of bottlenose dolphins and other

marine wildlife, the bay is designated as a Special Area of Conservation (SAC) under the European Union

habitats directive (Pierpoint et al., 2009).

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(a)

(b)

Figure 3: Map of the study site off the coast of Wales, United Kingdom. (a) Cardigan Bay with the Special

Area of Conservation (boxed area). (b) New Quay Bay, showing the location from where observations were

made and the survey area, boxed area, (Martin 2016).

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2.2 Surveys and Data collection for 2015

To investigate the impact of vessels on dolphin behaviour, a series of visual surveys were conducted from

New Quay in Cardigan Bay (52.215889º N, 4.359111º W) between May 1st and June 30th, 2015 (Figure 1b).

Surveys were conducted from the headland with the naked eye and using low powered binoculars, rather

than from vessels, in order to minimise any observer effects on dolphin behaviour. Also, observers on

headland were approximately 50-90 m above sea level, giving a high and unobstructed perspective of the

survey area. During the study period, five to seven surveys were conducted daily at predetermined periods;

beginning every two hours from 07:00-19:00. Each survey consisted of eight consecutive 15 min intervals

during which observations were made. Within each 15 min interval, numerous variables were recorded in

relation to dolphin-boat interactions (Appendix Two).

From the surveys, boat activity, type, and behaviour were categorised as independent variables that may

explain dolphin behaviours during dolphin-boat interactions. To estimate boat activity, it was recorded

whether or not a boat was present in the survey area during the observation interval. Next, all observed

vessels were further classified by boat type (Table 1) and boat behaviour. Boat behaviour was classified as

either positive or negative depending on whether the vessel was operated in accordance with the

Ceredigion Recreational Boat Users Code of Conduct (Ceredigion District Council, 2010; Table 2). Further,

any instances where boats came within 300 or 50 m of a dolphin were classed as either a standard or close

encounter, respectively; and, recorded the total number of boats that came within 300 m of a dolphin

during each observation period. Distance between boats and dolphins was estimated from fixed markers in

the bay including: the harbour wall, cardinal buoy and a fish factory.

To investigate dolphin activity, it was recorded whether or not dolphins were observed in the survey area

during each survey interval. Also recorded was the number of all other marine mammals observed during

each survey these included harbour porpoises, Phocoena phocoena, and Atlantic grey seals, Halichoerus

grypus. Dolphin activity was categorized into specific behaviours that represented a suite of staying,

feeding, playing, travelling, dispersion, and avoidance behaviours (see Table 3 for full list of dolphin

behaviours). Further, each of these specific behaviours were classed as a more general response: either

positive, neutral, or negative (Table 3). To determine how dolphins responded in each dolphin-boat

interaction, dolphin behaviours were recorded before and during boat encounters. A dolphin-boat

encounter was deemed to have commenced when a boat came within 300 m of a dolphin or group of

dolphins; any subsequent boats to enter the same area during this period were not noted.

15

Table 1: List of the categories of boats and their abbreviation observed in the surveys of Cardigan Bay,

Wales.

Code Boat Type

C Canoe, kayak, paddleboard

CF Commercial fishing boat

J Jet ski

MB Motor boat

O Other

R Research under licence

SB Speedboat

SCY Any boat under a sail including windsurfers

SS Water-skier

VPB Visitor passenger boats

Table 2: List of the manner in which boats were observed to be operated in surveys from Cardigan Bay,

Wales.

Specific boat behaviours are abbreviated to codes with the full description of the behaviour in the adjacent

cell. General boat behaviours are indicated with colour over the specific behaviour code. Green and red

indicate positive and negative behaviours, respectively, in accordance with the Ceredigion Recreational

Boat Users Code of Conduct (Ceredigion District Council, 2010).

Code of Conduct Code Definition

Y1 No wake speed and no erratic changes in course when passing

cetaceans.

Y2 Slowed down and gradually stopped.

N1 The bow/wake speed is too fast and white water is visible.

N2 Erratic course to follow or avoid cetaceans.

N3 Attempted to feed or touch the cetaceans.

N4 Exceeded 8kt within the yellow buoys

R Research vessel photographing

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Table 3: List of bottlenose dolphin (Tursiops truncatus) behaviours observed in surveys of Cardigan Bay,

Wales.

Specific dolphin behaviours are abbreviated to codes with the full description of the behaviour in the

adjacent cell. General dolphin behaviours are indicated with colour over the specific behaviour code.

Green, yellow, and red indicate positive, neutral, and negative behaviours, respectively.

Behaviour Code Definition

S1 Staying – Lying motionless at the surface like a log

S2 Staying – Slow circling and milling around at the surface

S3 Staying – long dives and foraging at depth

S4 Chasing prey at the surface

S5 Playing with jellyfish/seaweed or other objects

S6 Staying – Fast circling at the surface, leaping, tail slaps

T1 Travel – Regular surfacing with all animals in the group following

a consistent course and making determined progress

T2 Travel – Long dives and surfacing at irregular intervals

T3 Travel – Rapid progress with forward leaps

TS Tail Slapping

A Approaching or following the vessel

BR Bow Riding

BL Begin leaping

NC No change in behaviour

H Heading directly away from the vessel

GF Dolphins form a close, tight knit group

GS Group splits and disperses

D Disappears

2.3 Surveys and Data Collection for 2005 and 2010

To investigate long-term associations between dolphins and boats in Cardigan Bay, the data collected in the

2015 surveys were combined with two data sets collected in 2005 and 2010. The data from 2005 and 2010

were collected by volunteers under the direction of the Cardigan Bay Marine Wildlife Centre (CBMWC). In

17

Cardigan Bay, methods for surveys and data collection have been standardized since 1994 (Pierpoint et al

2009). Hence, the data collected in 2015 followed these procedures and are directly comparable across

years.

2.4 Data analysis

All data were collated in Microsoft Excel (version 2010) and analysed in SPSS (version 23). All of the boat

and dolphin variables recorded were categorical and quantified as frequencies. Hence for most analyses,

contingency tables were constructed by cross-tabulating boat and dolphin observations, so each cell in the

table represented one combination of a boat and dolphin variable. The observed frequencies of these data

were used to test whether the cells were significantly different. While straightforward analyses of

contingency tables do not distinguish between predictor and response variables, a priori the hypotheses

were focused on how boats influenced dolphin behaviour; hence as recommended by Quinn & Keough

(2002), the tables were structured by designating dolphin behaviours as the response variable and interpret

the data in this manner. SPSS calculated the expected frequencies as if the null hypothesis for each table

was true: i.e., the expected frequencies for each boat-dolphin observation are not different among cells.

The expected frequencies were then compared with the observed frequencies and were tested for

significant difference with χ2 tests. Overall, five sets of analyses that address specific questions about

dolphin and boat activity in Cardigan Bay were conducted.

The first analysis, was interested in testing the effects of year on the frequency of bottlenose dolphin

sightings relative to all other marine mammal species observe in the bay. For this analysis, the frequency

analysis was based on a table with two levels of sightings (bottlenose dolphin and non-bottlenose dolphin)

and three levels of years (2005, 2010, and 2015).

The second set of analyses looked at how two levels of boat behaviour (positive and negative) influenced

three levels of dolphin behaviour (positive, neutral and negative). This analysis was conducted twice: for

data from all years combined and for data from 2015. However for the 2015 data, two of the expected

frequencies were low (< 5), and therefore the χ2 test may be unreliable (Quinn & Keough, 2002). Hence, the

data was pooled for positive and neutral dolphin responses to achieve higher frequencies and meet the

assumptions of the χ2 test (Quinn & Keough, 2002). This research was also specifically interested in whether

the four visitor passenger boats influenced these results. So the above analysis was re-ran and omitted the

dolphin-boat interactions for the visitor passenger boat to test the effects of vessel behaviour on dolphin

responses (i.e., positive, negative, or neutral).

The third analysis looked at the frequency of dolphin behaviours in relation to different boat types.

However, canoes, kayaks, water-skiers, and jet-skis occurred at too low a frequency for analysis (Quinn &

18

Keough, 2002); so these data were pooled with the ‘other’ category. For this analysis there were two levels

of dolphin responses (positive and negative) and six levels of boat type (motor boats, commercial fishing

boats, sailboats, visitor passenger boats, speedboats and other).

The fourth set of analyses looked at how the presence of boats altered specific dolphin behaviours. The

frequency analysis consisted of two levels of a boat factor (presence or absence) and initially fourteen

dolphin behaviours. However, approaching vessels, bow riding, leaping, tail slapping, rapid travel, chasing

prey at the surface, and lying motionless occurred at low frequencies (<5 total observations), so these data

were pooled into a response variable ‘other’(Quinn & Keough, 2002). Therefore, the analysis was based on

six levels of dolphin behaviour (including: staying in the same area with slow circling and milling; long dives

and foraging at depth; fast circling at the surface; travelling with regular surfacing and long dives; and

‘other’; Table 3). This frequency analysis was repeated for data from all years combined, and data from

2005, 2010, and 2015, separately. The effects of boats on the specific behaviours was further investigated

by comparing the frequency of each dolphin response with pairwise z-tests prior to and during a boat

encounter.

The fifth analysis tested whether boat activity changed among 2005, 2010, and 2015. For each year (three

levels: 2005, 2010, and 2015), the frequency of boats present or absent from the survey area was recorded

during the survey period, and compared the cells with frequency analysis.

3.0 Results

3.1 Observations and Sightings

Over the 10 year study period (2005 to 2015), a total of 6333 observations were made in Cardigan Bay, of

which 2501 reported sightings of bottlenose dolphins. Between 2005 and 2015, the number of bottlenose

dolphin sightings increased from 396 to 1458, which corresponds to 28.7% and 49.0% of the total number

of all observations within the given year (Table 1a). A Chi-square test revealed the increase in bottlenose

dolphin sightings was statistically significant (2, N=6333 = 218.140a P= 0.000) (Table 1b).

19

Table 4: Summary statistics for the number and percentage of bottlenose dolphin sightings recorded

between 2005 and 2015 in Cardigan Bay, Wales.

(a) Count and percentage data presented as summaries for sightings of bottlenose dolphins and non-

bottlenose dolphins. BND = bottlenose dolphins.

(b) Summary statistics for the frequency analysis testing the effects of year on bottlenose dolphin sightings.

3.2 Hypothesis One

Question 1: Do the dolphins have positive or negative reactions to boat encounters?

Over the 10 year study period, a total of 589 dolphin-boat interactions were observed. During the

interactions, most of the vessel behaviour was classified as positive (88.8%), and negative vessel behaviour

was rare (11.2%). Throughout this period, dolphins were observed to respond to the presence of boats with

negative, neutral and positive behaviours. Overall, neutral dolphin responses were observed the most

often, accounting for 75.6% of the total observations; positive and negative behaviours were observed

16.6% and 7.8% of the time, respectively (Figure 1). The Chi-square test confirmed the different frequencies

observed among dolphin behaviours were significantly different (2, N=590 = 60.669, P = 0.000) (Table 2).

20

Interestingly, these overall effects were not consistent among vessel behaviours. Dolphins that experienced

positive vessel behaviour demonstrated similar levels of positive (16.6%) and negative (16.75%) responses

(Figure 1). But, when the vessels acted negatively, the percentage of dolphins that exhibited negative

responses was more than 6 times higher compared to when the vessels acted positively (from 4.8% to

31.8%, respectively; Figure 1). Reciprocally, the amount of neutral behaviours dropped from 78.6% in

positive vessel interactions to 51.5% in negative vessel interactions (Figure 1).

Figure 4: Summary of all observed dolphin-vessel interactions grouped by vessel behaviours (top panel,

positive vessels; bottom panel, negative vessels) and bottlenose dolphin (Tursiops truncatus) behavioural

responses (positive, neutral and negative) in Cardigan Bay, Wales, from 2005, 2010 and 2015. Each bar

represents to the total count of observed dolphin behaviour with the overall number of observations

totalling 590.

21

Table 5: Summary statistics for the frequency analysis testing the effects of vessel behaviour (two levels:

positive and negative) on dolphin (Tursiops truncatus) behaviour (three responses: positive, neutral and

negative) in Cardigan Bay, Wales in 2005, 2010, and 2015.

For 2015, the results from the initial analysis indicated that the general trends reported across all time

periods remain present. Again, neutral behaviours were the most common (observed in 83.3% of dolphin-

boat interactions). However, positive dolphin behaviours were observed less frequently in 2015 than across

all time periods combined (Figure 2), and were similar in frequency to negative behaviours in 2015 (8.1%

and 8.7% of the total observations, respectively; Figure 2). Similar to the overall data, positive dolphin

responses appeared to be independent of vessel behaviour: dolphins responded positively in 8.1% and

7.7% of positive and negative vessel interactions, respectively. Further, the frequency of neutral and

negative dolphin responses depended on vessel behaviours: again, negative vessel behaviour increased the

frequency of negative dolphin responses from 5.4% to 33.3% (Figure 2). While the Chi-square tests

suggested these relationships among vessel behaviour and dolphin responses were statistically significant

(2, N=335= 34.187, P= 0.000), two of the expected frequencies were low (< 5), and therefore the Chi-

squared test may be unreliable (Table 3a). However, when the data for positive and neutral dolphin

responses were pooled to achieve higher frequencies and meet the assumptions of the Chi-square test, the

result was statistically significant (1, N=335= 33.991, P= 0.000) (Table 3b). Here, vessel behaviour caused

dolphins to respond positively/neutrally in 94.6% of positive vessel interactions and 66.7% in negative

vessel interactions (Figure 2).

22

Figure 5: Summary of observed dolphin-vessel interactions grouped by vessel behaviours (top panel,

positive vessels; bottom panel, negative vessels) and dolphin (Tursiops truncatus) behavioural responses

(positive, neutral and negative) in Cardigan Bay, Wales, from 2015. Each bar represents to the total count

of observed dolphin behaviour.

23

Table 6: Summary statistics for frequency analysis testing the effects of vessel behaviour (two levels:

positive and negative) on dolphin (Tursiops truncatus) behaviour (three responses: positive, neutral and

negative) in Cardigan Bay, Wales in 2015.

(a) Result of the full frequency analysis with all levels of boat and dolphin behaviour

(b) Results of the pooled frequency analysis with positive and neutral dolphin behaviours pooled.

3.3 Dolphin Reactions to Specific Vessel Types

Another aim of this study was to investigate whether the type of boat influenced dolphin responses to

vessel activity. On average, 64% (± 0.809 SD) and 60% (±0.809 SD) of dolphins responded positively to

speed boats and commercial fishing boats (Figure 3). Sail boats and the visitor passenger boats did not

appear to be favourable or unfavourable to dolphins, as both elicited positive dolphin behavioural

responses - 50% (± 0.894 SD) and 52 % (± 0.863 SD) of the time, respectively. Motor boats rarely caused

dolphins to respond positively with only 2% (± 1.011 SD) of dolphin responses to motor boats being

positive. Dolphins responded positively to all other boat types in 17% (± 1.03 SD) of observations.

3.4 Hypothesis One with VPB Vessel Type Removed

It was also hypothesised that dolphins may have become habituated to the four visitor passenger boats

that routinely interact with the dolphins on most days. When the dolphin-boat interactions for the visitor

24

passenger boat were omitted and the analysis testing the effects of vessel behaviour on dolphin responses

(i.e., positive, negative, or neutral) reran it was found that these results did not differ from the overall

results, suggesting that visitor passenger boats have little influence on dolphin behaviour compared to

other types of boats.

Figure 6: The effects of boat type on the proportion of positive bottlenose dolphin (Tursiops truncatus)

responses in Cardigan Bay, Wales. X-axis labels for boat type are abbreviated: MB = motor boat, Other = all

other boat types, SCY = sail boats, VPB = visitor passenger boat, CF = commercial fishing boat, and SB =

speed boat.

25

3.5 Hypothesis Two

Question 2: Does the variety of dolphin behaviour decrease when boats are present?

A total of 2498 observations of dolphins in 14 positive activity states were recorded during the study.

Across all time periods, dolphins were observed staying in an area and conducting long dives and foraging

more frequently than all other behaviours (46.2%). Slow circling (including milling) and fast circling

(including leaping and tail slaps) on the surface were the next most frequently observed, accounting for

20.4 and 11.3% of the total behavioural states observed, respectively (Figure 4a). Travelling with regular

surfacing in consistent groups, travelling with long dives surfacing at regular intervals, and all other

behaviours were each observed less than 10% of the time. In most instances, the different types of

behaviours occurred at frequencies that appeared to be independent of whether a boat was present or

absent (Figure 4a). Although, the Chi-square test revealed a significant difference (5, N=2498= 18.810, P=

0.002) in the distribution of the responses suggesting that some of the behaviours varied among the

presence or absence of boats (Table 3a). Travelling with long dives showed the largest reduction in

frequency when boats were present (from 8.5% to 5.4%); and, slowing, circling and milling on the surface

increased the most when boats were present (from 19.7% to 22.7%; Figure 3).

Within each year, staying in an area and conducting long dives and foraging was consistently the most

commonly observed dolphin behaviour. However, the relative proportion of this behaviour, compared to

the other behaviours, varied among years. In 2010, 67.4% of dolphins were observed conducting long dives

and foraging compared to 53.4% and 34.9% in 2005 and 2010, respectively. Similarly, slow circling and fast

circling were the next most commonly observed behaviours, but in 2015, slow circling was more prevalent

than it was across all time periods combined. In 2015, slow and fast circling were observed in 29.8% and

17.6% of interactions, respectively; but in 2005 and 2010, slow and fast circling had the lowest frequency of

all of the non-pooled behaviours (2005: slow 8.6%, fast 3.3%; 2010: slow 6.2%, fast 2%). Travelling at any

speed was observed to be less than 12% across all time periods. Of the two travel behaviours, travel with

regular surfacing was the most consistent among years; recorded as 9%, 10.9%, and 10.1% for 2015, 2010,

and 2005, respectively. Travel with long dives and irregular surfacing was more variable and was found to

be highest in 2010 (11.6%), intermediate in 2005 (10.4%), and lowest in 2015 (5.3%). The percentage of all

other behaviours was also highly variable among years: 2005 was the highest (14.2%), which was nearly 3

and 7 times more than in 2015 (5.3%) and 2010 (1.9%).

The influence of boat activity on dolphin activity states was inconsistent among years. In 2010, the Chi-

square test revealed there was no significant effect of the presence or absence of boats on the diversity of

dolphin behaviours (5, N=644= 4.892, P= 0.429) (Table 3c); and in 2005, this effect was marginally non-

26

significant (5, N=395= 10.849, P= 0.054) (Table 3b). However, in 2015 the diversity of dolphin behaviours

was found to be significantly different among the presence or absence of boats (5, N=1459=13.878, P=

0.016) (Table 3d). When boats were present in 2015, dolphins exhibited higher percentages of slow and

fast circling, and all pooled behaviours, but lower percentages of staying with long dives and foraging, and

travelling with regular and irregular intervals (Figure 4b).

27

(a) Data from all years combined

(b) Data from 2015

Figure 7: The effects of the presence or absence of boats on the frequency of behavioural responses for

bottlenose dolphins (Tursiops truncatus) in Cardigan Bay, Wales. X-axis shows abbreviations for the dolphin

activity states: S2, staying with slow circling and milling; S3, staying with long dives and foraging; S6, staying

with fast circling; T1, travelling with regular surfacing; T2, travelling with long dives and irregular surfacing;

Other, all other behaviours.

28

Table 7: Summary statistics for frequency analysis testing the effects of the presence of absence of boats

on the variety of dolphin (Tursiops truncatus) behaviours in Cardigan Bay, Wales in 2015.

(a) All years

(b) 2005

(c) 2010

29

(d) 2015

Boat activity did not appear to change the type of behaviour dolphins exhibited during most of the

interactions. When the percentage of each dolphin response was compared using pairwise z-tests prior to a

boat encounter and during the encounter, there was no significant difference in T1 (N=78= -0.236, P=

0.810), T2 (N=52= -0.570, P= 0.57), S2 (N=234= -0.447, P= 0.57) and S6 (N=127= -0.095, P= 0.93) (Table 4).

For the five most common dolphin behaviours (including slow and fast circling, long foraging dives, and

travel with regular and irregular surfacing), the greatest difference was observed for the long dives and

foraging behaviour, where dolphins increased the amount of long dives and foraging by only 1.6% during

the encounter (Figure 5), which was not statistically different (N=482= 0.504, P= 0.62) (Table 4).

Table 8: Summary statistics for pairwise z-test analysis testing whether dolphins changed activity state prior

to and during an encounter with a boat in Cardigan Bay, Wales in 2015. Only the five most common dolphin

activity states were tested. Activity states abbreviated: S2, staying with slow circling and milling; S3, staying

with long dives and foraging; S6, staying with fast circling; T1, travelling with regular surfacing; T2, travelling

with long dives and irregular surfacing.

Prior During Z P

T1 40 38 -0.236 0.81

T2 28 24 -0.570 0.57

S2 120 114 -0.447 0.65

S3 237 245 0.504 0.62

S6 64 63 -0.095 0.93

506 506

30

Figure 8: Graphical representation of dolphin activity states prior to and during an encounter with a boat in

Cardigan Bay, Wales, in 2015. Activity states on the x-axis abbreviated: S1, motionless lying; S2, staying with

slow circling and milling; S3, staying with long dives and foraging; S4, chasing prey on surface; S6, staying

with fast circling; T1, travelling with regular surfacing; T2, travelling with long dives and irregular surfacing;

T3, rapid travel; TS tail slapping With prior referring to before the vessel encounter and the during bar

referring to the behaviour during the vessel encounter.

3.6 Hypothesis Three

Question 3: Has boat traffic increased since 2005?

From 2005 to 2015, a total of 1299 hours were spent observing the presence or absence of boats within the

study area. Overall, boats were present 23.7% of the time and absent 76.3% of the time (Table 5). Among

years, boat activity initially increased from 21% in 2005 to 27% in 2010. However, an increase in boat

activity did not persist, and in 2015 boat activity decreased to 22.9%. The Chi-square test confirmed that

the proportion of boats present or absent were significantly different (2, N=2498=6.031, P=0.049) (Table 6).

Hence, overall there was no significant increase or decrease in boat activity in Cardigan Bay between the

years 2005, 2010 and 2015.

31

Table 9: Summary data for the number and percentage of times boats were present of absent during

surveys of the in Cardigan Bay, Wales, in 2005, 2010, and 2015.

Table 10: Summary statistics for frequency analysis testing the effects of year (three levels: 2005, 2010, and

2015) on the presence of absence of boats in Cardigan Bay, Wales.

4.0 Discussion

4.1 Dolphin Abundance

Cardigan Bay on the western coast of Wales supports a substantial population of bottlenose dolphins. From

2005 to 2015, there was an increase in the frequency (compared to all other marine mammals) of

bottlenose dolphin sightings; suggesting the local bottlenose dolphin population is healthy, and may be

increasing. The data collected follows reports of a similar increase in dolphin abundance in the bay from

1994 to 2007 (Pierpoint et al., 2009). Further, at population level, there is little evidence to suggest boat

activity is related to dolphin abundance – at least not in more recent times. From 2005 to 2015, boat

activity did not change in frequency, and so the observed increase in dolphin sightings was independent of

boat activity. The current dolphin population may be benefiting from a persistent positive effect on the

32

population caused by protective measures initiated in the early 1990s to restrict some boat activity

(Feingold & Evans, 2013).

While bottlenose dolphins in Cardigan Bay did not appear to be affected by boat activity at the population

level, dolphin-boat interactions were commonly observed among individuals and groups of dolphins with a

variety of vessels.

4.2 Dolphin Reaction to Vessel Encounters

In most dolphin-boat interactions, boat operators followed the local code of conduct (Ceredigion District

Council, 2010) with nearly 90% of boats demonstrating positive behaviour towards dolphins. Most dolphins

appeared to be unperturbed by boats and showed neutral responses in 75% of all boat interactions and

only 7.8% of dolphins responded negatively. A similarly high prevalence of neutral dolphin-boat

interactions has been previously reported for the dolphins in Cardigan Bay (Gregory & Rowden, 2001);

although, the frequency of neutral behaviours was higher in the current study than reported by Gregory

and Rowden (2001). The increase in neutral behaviour more recently could indicate the dolphins in the bay

are becoming increasingly habituated to boat activity over time, which has been reported for bottlenose

dolphin populations in New Zealand (Constantine, Brunton & Dennis, 2004) and Scotland (Sini et al., 2005).

However not all dolphin-boat interactions were benign. When boats were operated in a negative and

potentially threatening manner, dolphins responded negatively over three times more frequently than in

any other context. Hence, even though most boats were operated positively and most dolphins reacted

neutrally, negative boat operation may still pose a threat to the dolphins, as many other studies commonly

show negative dolphin-boat interactions can be detrimental to dolphin energy budgets, foraging regime,

communication, mating, and habitat use (Christiansen et al., 2010; Constantine, Brunton & Dennis, 2004;

Hastie et al., 2003; Lusseau,, 2005). However, the negative dolphin-boat interactions within Cardigan Bay

do not appear to be sufficiently strong to manifest at the population level, based on the data in the present

study that suggests an overall increase in the abundance of dolphins. One potential avenue of future

research could be to quantify the costs of negative dolphin-boat interactions on dolphin energy budgets,

foraging ability and reproductive success, to investigate whether these effects can explain some variance in

dolphin abundance during certain years.

4.3 Dolphin Reactions to Specific Vessel Types

This research focused on the relationship between the types of vessels involved in dolphin-boat

interactions mediated dolphin responses. Dolphins responded positively to speed boats and commercial

fishing boats. Speed boats and other vessels that move at high speeds have previously been shown to

attract dolphins that bow ride in the wake of vessels (Hawkins & Gartside, 2009). Similarly, dolphins are

33

commonly reported to be attracted to commercial fishing vessels, where there is the opportunity to obtain

food from fishing bycatch (Chilvers & Corkeron, 2001). Although, whilst dolphins may perceive interactions

with speed and fishing boats as positive, these types of dolphin-boat interactions are not natural, and in the

long-term may be detrimental to dolphins (Chilvers & Corkeron, 2001; Prideaux, 2012). Dolphins appeared

to be unaffected by sail boats and visitor passenger boats. Motor boats were the only type of boat that

consistently caused dolphins to react negatively. There are two primary ways motor boats may harm and

distress bottlenose dolphins and be responsible for eliciting the negative responses. First, motor boat

propellers can cause severe injury to dolphins (Prideaux, 2012). Second, the noise created by boat engines

underwater occur at similar frequencies, harmonisations and tones to the noises dolphins use to

communicate, navigate and locate food (Hastie et al., 2003, Pirotta et al., 2015). Hence, the result in the

present study of negative encounters with motor boats is not surprising and is consistent with previous

studies (Hastie et al, 2003; Pirotta et al., 2015; Prideaux, 2012). In the future, conservation protocols could

specifically target motor boats as they appear to be the most pertinent boat threat to dolphins in Cardigan

Bay.

4.4 Dolphin behaviour dependent and independent of Vessel Interactions

The most commonly observed specific dolphin behaviours were all staying behaviours (i.e., dolphins stayed

within the observation area). Within the “staying” category, most dolphins conducted long dives and

foraging, followed by slow (including milling) and fast circling. Importantly, boat-activity also had a minimal

effect on these specific behaviours because most of the behaviours occurred independently of whether a

boat was present or absent. Further, when the frequency of each specific dolphin behaviour was compared

before and during encounters with boats, there was no change. Overall, this suggests dolphins in most

dolphin-boat encounters were unaffected by boats, and continued to exhibit natural behaviours. However,

many of these results contrast with previous studies on bottlenose dolphin populations that usually show

some change in behaviour when boats and dolphins are within the same vicinity. Although, how dolphins

respond – positively or negatively – varies among studies and locations. Many studies report dolphins

respond to boat encounters by changing their behaviour in a negative way. For example, dolphins off the

coast of Zanzibar were more likely to cease resting and socialising behaviours to travel away from an area a

boat has entered (Christiansen et al., 2010). Indeed travelling away from an area appears to be the most

common negative change in the behavioural state of bottlenose dolphins reported among studies

(example: Arcangeli & Crosti, 2009; Christiansen et al, 2010; Gregory & Rowden, 2001; La Manna et al.,

2013). Within the population, variations in specific dolphin behaviours is also observed to change before

and during boat encounters. In Scotland, dolphins changed behaviour to bow ride, surf and breach around

large vessels, but often moved away and exhibited prolonged avoidance-like dives around smaller boats

(Sini et al., 2005). In the present study, there were two exceptions to the overall trend of no change in

34

behaviour before and during boat encounter; these included a decrease in the frequency of dolphins

travelling with long dives and an increase in the frequency of staying with slow circling and milling during

boat encounters. This suggests dolphins were ceasing their pre-boat behaviour and either waiting for the

boat to pass before going back to the original state or stopped because they were interested in the boat.

This is because dolphins are attentive to novel stimuli (Sini et al., 2005). Similar results of this type of

neutral change in behaviour are reported in New Zealand, where dolphins did not ignore an approaching

boat, and exhibited more milling behaviour during the boat encounters (Constantine, Brunton & Dennis,

2004).

4.5 Potential Consequences of Continued Vessel Interactions

Some authors of previous studies have suggested that when dolphins respond to boats by vacating an area

and are repeatedly exposed to boat traffic over long time periods, the outcome may lead dolphins to

permanently leave an area or expand their home-range (Lusseau, 2005). An alternative outcome to

vacating an area of high boat traffic is for dolphins to simply become habituated to the boat traffic, which

has been reported in other coastal areas of Britain (Sini et al., 2005). In the present study, while there was a

significant amount of variance in the frequency of specific (e.g., staying or bow riding) and general (positive

or negative) behaviours exhibited among survey years, overall there was no trend indicating any change in

dolphin behaviour or dolphin-boat encounters over time. Hence, dolphin-boat interactions appear to be in

some form of equilibrium in Cardigan Bay – supporting the possibility that the dolphins in Cardigan Bay are

habituated to boat activity with the only exception coming from noise-disturbance created by motor boats.

These results are contrary to a study conducted in the fjords of southern New Zealand that suggested local

dolphins avoid one particular fjord, characterised by very high levels of tourist boat activity, and instead

reside in one of the other fjords that are not visited by tourists (Lusseau, 2005).

4.6 Future Research

If this investigation were to be continued it could be improved upon in several ways. Firstly the data

collection forms could be improved by recording all of the boat encounters that occurred within the fifteen

minute period as opposed to the current method of only recording the first dolphin-boat encounter. This

would allow a greater analysis of dolphin-boat encounters by having a greater number of data points for

analysis. It would allow an investigation into prolonged boat exposure and the effects of multiple boat

interactions which could lead to the dolphins evacuating Cardigan Bay. The data collection could also be

improved upon by having one researcher or a smaller number of dedicated researchers collecting the data

rather than multiple volunteers. This would standardise the data as the distances would be the same and

there is no difference in opinion of the exhibited behaviours.

35

Another valuable extension to this investigation would be to have two different observation points and

survey areas. Ynys Lochtyn would be a viable survey point and was previously used as an observation point

by Gregory and Rowden (2001). This additional survey area would not only increase the amount of data

points but also allow a different insight into dolphin-boat reactions as this survey area does not have a

constant stream of vessels. This lack of vessels limits the dolphins’ familiarity to them and therefore the

dolphins’ reactions are more likely to be genuine rather than a learned reaction.

The research could also be extended to run from April through to the September to be conducted

throughout the summer season when boat traffic is at its greatest rate. This would generate a greater

number of data points for analysis. This combined with a new data collection sheet to record all boat

encounters, could give a greater insight into dolphins having multiple dolphin encounters within a short

period of time. In addition to whether a dolphin having multiple encounters in a short time gleans more

negative encounters rather than single encounters.

For a more thorough analysis, instead of analysing the data five years apart, the data from each individual

year could be analysed. This would give a more accurate representation of dolphin abundance. It would

also allow trends to be found in dolphin abundance and in behaviours which may be more prevalent at

different times of the year or times of the day.

5.0 Conclusion

In conclusion, the bottlenose dolphins of Cardigan Bay appear to be a strong, and potentially increasing,

population. Early interventions by the local government that restrict some boat activities, and the more

recent protective measures from the European Union, appear to be benefiting the dolphins. In addition, the

majority of vessel operators are also following the guidelines. Unlike some populations of bottlenose

dolphins in other parts of the world, the dolphins of Cardigan Bay appear to be well accustomed to the

activities of a variety of vessels. Although, a small number of motor boats and poorly operated vessels may

still be causing problems for dolphins. Future research and management regimes may look to these specific

dolphin-boat interactions to enhance the protection of the dolphin in Cardigan Bay.

36

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Stone, G. S. & Yoshinaga, A., 2000. Hector’s dolphin Cephalorhynchus hectori calf mortalities may indicate

new risks from boat traffic habituation. Pacific Conservation Biology, 6,162-170.

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Wilson, B., Thompson, P. M. & Hammond, P. S., 1997. Habitat use by bottle-nosed dolphins: Seasonal

distribution and stratified movement patterns in the Moray Firth, Scotland. Journal of Applied Ecology, 34,

1365-1374.

Wursig, B. and Wursig, M., 1979. Behavior and ecology of the bottlenose dolphin, Tursiops

truncatus, in the south Atlantic. Fishery Bulletin, 77(2), pp.399-412.

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Appendix One

In general keep a good look out and keep your distance. Do not approach marine mammals, let

them come to you. Headlands and reefs such as Mwnt, Aberporth, Ynys Lochtyn, New Quay and

Sarn Cynfelyn are very important feeding areas for dolphins and porpoises; take extra care to travel

slowly and not to disturb animals in these areas. Please operate all boats with care and attention

for the safety of occupants and respect for all other sea users. Do not discard litter or fishing

tackle at sea.

Dolphins, Porpoises & Seals

If these creatures are encountered at sea please:

Slow down gradually to minimum speed. Do not make sudden changes in speed or course.

Do not steer directly towards them or approach within 100m.

Do not attempt to touch, feed or swim with them.

Take extra care to avoid disturbing animals with young.

Do not approach seals resting on the shore, and do not enter sea caves during the pupping season

(1st of August to 31st of October

Avoid any unnecessary noise near the animals.

Birds

Keep out from cliffs in the breeding season, 1st of March to the 31st of July

Avoid any unnecessary noise close to cliffs.

Keep clear of groups of birds resting or feeding on the sea.

This code applies to all recreational vessels including motor boats, yachts, dinghies, personal

watercraft, kayaks and canoes. Always comply with requests from the local patrol boats and be

aware of speed restrictions around bathing beaches and wildlife sites.

Note that Ceredigion Harbourmasters and Launch Control Officers are authorised to withdraw

launching and/or mooring permits from vessels and individuals not observing local regulations,

byelaws or the Ceredigion Marine Code. Deliberate or reckless disturbance of any protected

species (such as dolphins) is a criminal offence.

Ceredigion County Council Department of Environmental Services and Housing

Ceredigion Marine Code

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