Proceedings of the Ecs Workshop

PROCEEDINGS OF THE ECS WORKSHOP

GRAMPUS GRISEUS 200TH ANNIVERSARY: RISSO’S DOLPHINS IN THE CONTEMPORARY WORLD

Held at the European Cetacean Society’s 26 th Annual Conference Galway, Ireland, 25 th March 2012

K. Hartman, Nova Atlantis Foundation

Editors: Ing Chen, Karin Hartman, Mark Simmonds, Anja Wittich and Andrew J. Wright

ECS SPECIAL PUBLICATION SERIES NO. 54 November 2013

WEB VERSION

Disclaimer: The following report is from a workshop held in conjunction with, but not as part of, the 26 th meeting of the European Cetacean Society. The following report results from ECS efforts to provide a venue for recording the discussions and disseminating them to members unable to attend. Unless specifically noted, the contents are the sole responsibility of the workshop organisers and do not necessarily represent the opinion of the ECS Council, Scientific Committee or Membership.

The ECS claims no copyright, which remains with the authors. Authors should be contacted directly if the contents are to be reproduced elsewhere. The ECS undertook no peer review of the contents of this report. Furthermore, while the ECS has taken steps to ensure that any work reported here was conducted to the scientific and ethical standards required for presentation at the ECS conference, ultimate responsibility for this also falls to the workshop organisers. Thus, the ECS does not accept any responsibility for the information that follows.

Editors: Ing Chen 1, Karin Hartman 2, Mark Simmonds 4, Anja Wittich 2 and Andrew J. Wright 5

1 School of Biological and Biomedical Sciences, University of Durham. South Road, Durham, DH1 3LE, UK 2 Nova Atlantis Foundation, Rua Doutor António Freitas Pimentel 11, 9930-309 Santa Cruz das Ribeiras, Lajes do Pico, Azores, Portugal 3 WDCS. Brookfield House, 38 St Paul Street, Chippenham, Wiltshire, SN15 1LJ, UK 4 Humane Society International, c/o 5 Underwood Street, London N1 7LY, UK 5 European Cetacean Society.

Citation: Chen, I., Hartman, K., Simmonds, M., Wittich, A. and Wright, A.J. (Eds.) 2013. Grampus griseus 200th anniversary: Risso’s dolphins in the contemporary world. Report from the European Cetacean Society Conference Workshop, Galway, Ireland. European Cetacean Society Special Publication Series No 54, 108 pages.

CONTENTS

1. Introduction ...... 7

2. ECS Resolution on the need to regulate sonar mitigation ...... 9

Session 1) Presentations for Risso’s dolphin studies ...... 10

3. Evans, P. The Risso’s dolphin in Europe: research and conservation ...... 10

4. Wall, D. et al. Current state of knowledge of the distribution and relative abundance of Risso’s Dolphins ( Grampus griseus ) in Irish waters...... 25

5. De Boer, M.N. et al . The fine-scale habitat use of Risso’s dolphins ( Grampus griseus ) off Bardsey Island, Cardigan Bay (UK) ...... 32

6. Dolman, S.J. et al . Land and boat-based observations of Risso’s dolphins off North- east Isle of Lewis, Scotland from 2010 to 2012 ...... 44

7. Remonato, E. et al. Study of residency patterns, home ranges and movements of Risso’s dolphins ( Grampus griseus , Cuvier, 1812) in the western Ligurian Sea...... 54

8. Hartman, K.L. et al. Show me your body and I tell you how old you are: A non- invasive method to define 6 life history- classes in Risso’s dolphins ( Grampus griseus ) using an identified trial population in the Atlantic ...... 69

9. Chen, I. and Chou, L.-S. A brief review on Risso’s dolphins off Taiwan: ecological and biological characters, and potential anthropogenic threats ...... 89

10. Jepson, P. and Deaville, R. Information about Risso’s dolphins from the UK Cetacean Stranding Investigation Programme (CSIP) [Post-workshop submission]...... 100

Session 2) Conclusive remarks from the discussion panel: conservation actions ...... 104

11. Simmonds M. et al . Call for action for Risso’s dolphin in the North East Atlantic Region ...... 104

1. INTRODUCTION

Mark Simmonds 1,2

1 Humane Society International, c/o 5 Underwood Street, London N1 7LY, UK. 2 Previoustly at Whale and Dolphin Conservation (WDC), Brookfield House, 38 St Paul Street, Chippenham, Wiltshire, SN15 1LJ, UK

The lookout perched above the prow excitedly calls into his hand-radio. It is the first day of the survey and he reports that there is a dolphin swimming along in front of the bow-wave, and not just any dolphin but a genuine Risso’s dolphin, Grampus griseus; in fact, the same ‘little-known’ species that he had avidly described earlier to the crew! Half the crew, including the skipper, come running to see this ‘legendary’ animal but, as they climb up the steps to the view-point, the animal nonchalantly, and without the slightest splash, disappears below the water surface.

Neither it, nor any other representative of its species, was seen again during the several weeks that this particular survey swept to and fro in the offshore waters of Cardigan Bay. The lookout suspected that the crew probably did not believe him. The year was 2002 and the boat was the splendid Rainbow Warrior II, which had been kindly loaned by Greenpeace to allow some offshore survey work to be conducted in the waters to the west and south shores of the UK (De Boer and Simmonds 2003). It proved to be an excellent research platform (very stable), and I was that unfortunate lookout up on the prow. I had partly sold the offshore survey to my friends at Greenpeace to fill in some data-gaps left by previous surveys and partly specially to help with studies of the elusive Risso’s. They species was known from the Irish Sea but its distributions and movements were far from clear. For these waters, this fleeting encounter was not unusual and in the better part of the two decades that I have been encouraging surveys focused on Risso’s in the northern part of Cardigan Bay (and occasionally being fortunate enough to join them myself), this species has been a difficult target. The Whale and Dolphin Conservation Society managed these expeditions supported by CCW (guided by an enthusiastic Mandy McMath) and many other sponsors. Hence, it gives me great pleasure to see amongst the papers published in this workshop report two covering a long number of years from this research alongside new research on this species by the recently renamed WDC in the neighbouring waters off Scotland.

My fascination with this species perhaps stems from the fact that it is the large (3-4 m) gregarious, grey dolphin that is not the familiar bottlenose. To an untutored eye and from a quick glance they may appear similar, but the blunt face, the creased melon, the remarkable heavy adult scarring and the unique dentition (no teeth in the upper jaw and 2-7 large conical teeth below) of the Risso’s all point to a very different biology. And when we look more carefully, we find further evidence that this is a dolphin unlike any other: they have a uniquely angled sonar (Phillips 2003); a diet focused on mesopelagic squid; and a highly stratified social structure (a fascinating new discovery thanks to the commitment of Hartman and her colleagues working around the Azores) (Hartman et al ., 2008).

Risso’s are currently seen as a widespread species, although I wonder if they should actually be treated as a single global species anymore that Orcinus orca should – time

7 will tell! I think it is true to say that they remain little studied anywhere with the exception of the Azores. Giovanni Bearzi and his colleagues who provided an excellent recent review, certainly agreed with this sentiment (Bearzi et al ., 2010), although I might take issue with their observation that ‘Risso’s dolphins are not particularly shy or elusive and can be studied with relative ease…’. As this workshop report illustrates, this seems to be depend where you are attempting to study them!

Bearzi et al. (2010) focused on the Mediterranean, where they recorded that Risso’s dolphins occurred in continental slope waters throughout the basin and around many of the region’s offshore islands and archipelagos. They also found that the dolpins’ densities and overall numbers were low in comparison to other small odontocetes. The principal known threat to Mediterranean populations is entanglement in pelagic drift gillnets and Bearzi et al. suggested that other potential problems for Risso’s dolphins in the Mediterranean include noise disturbance and ingestion of plastic debris. Some years ago a colleague and I drafted a conservation plan for Risso’s dolphins in the waters west of the UK (Wharam and Simmonds 2008). We had little go on, but we highlighted the same threats and suggested some actions, including the need for more research. Now –after this workshop - we shall all be in a better position to rethink and improve such conservation plans.

In concluding this introduction I would like to paraphrase Bearzi et al. (2010): The distribution, ecology, status and trends of this species still remains ‘somewhat mysterious’ – a situation which hampers conservation but also makes and exciting situation for novel studies. After this workshop, as you will see as you turn these pages, we now know a lot more, but there is certainly more to come. In the meantime, the vulnerability of the species has become clearer and if we want to conserve it we need to act expeditiously in its best interests whilst maintaining our researches.

REFERENCES

Bearzi, G., Reeves, R.R., Remonato, E., Pierantonio, N. and Airoldi, S. 2011. Risso's dolphin Grampus griseus in the Mediterranean Sea. Mammalian Biology , 76, 385-400.

DeBoer, M. and Simmonds, M.P. 2003 WDCS/Greenpeace Survey Report. Small cetaceans along the coasts of Wales and Southwest England. A WDCS Science Team Report. 43 pp. Available at: http://www.wdcs-de.org/docs/WDCS_Greenpeace.pdf .

Hartman, K.L., Visser, F. and Hendricks, A.J.E. 2008. Social structure of Risso’s dolphins ( Grampus griseus ) at the Azores: A stratiﬁed community based on highly associated units. Canadian Journal of Zoology , 86, 294–306.

Philips, J.D., Nachtigall, P.E., Au, W.W., Pawloski, J.L. and Roitblat, H.L. 2003. Echolocation in the Risso’s dolphin, Grampus griseus. Journal of Acoustical Society of America , 113, 605–616.

Wharam, J and Simmonds, M.P. 2008. Risso’s Dolphin Conservation Plan for waters west of the UK. A WDCS Science Team Report. 25 pp. Available at: http://www.wdcs.org/submissions_bin/Rissos_Conservation_Plan.pdf .

2. ECS RESOLUTION: CALL FOR ACTION FOR RISSO’S DOLPHIN IN THE NORTH EAST ATLANTIC REGION

Adopted at ECS Annual General Meeting (AGM) in Setúbal, Portugal on 10 th April 2013

BACKGROUND

Recently, and as described at the ECS 2012 workshop (ECS 2013 In Prep), a new picture has emerged about the particular social structure of Risso’s dolphins; their discontinuous distribution and regular use of certain habitats; the disturbance and harassment affecting them in some places; the relatively small size of many local populations; and their potential high vulnerability to anthropogenic impacts, particularly noise pollution. However, all these issues are still compounded by an overarching lack of data, which means that precautionary actions to conserve them will be needed. These should include protecting Risso’s dolphins from all anthropogenic impacts, particularly bycatch and intense noise, and also, as the 2012 ECS workshop concluded, the development of specific measures for their conservation within marine protected areas in appropriate localities where the species has been found to regularly occur in numbers.

RESOLUTION

Noting: the support from the experts gathered in the 2012 ECS Workshop on Risso’s dolphins 1 for a call for action to help better protect this species across the region; and growing evidence of i. the isolation of populations, in particular in the NE Atlantic; ii. the existence of critical habitat areas, including in the Azores and the UK; iii. evidence of disturbance in the nursery grounds; iv. the vulnerability of this species to human impacts; and v. a general lack of information.

The ECS therefore: calls for urgent attention to be paid to the conservation of this species, particularly the establishment of protected areas and other appropriate measures for this species and recommends its inclusion in Annex II of the Habitats Directive.

1 Chen, I., Hartman, K., Simmonds, M., Wittich, A. and Wright, A.J.. (Eds.) 2013. Grampus griseus 200th anniversary: Risso’s dolphins in the contemporary world. Report from the European Cetacean Society Conference Workshop, Galway, Ireland. European Cetacean Society Special Publication Series No 54, 108 pages 9

3. THE RISSO’S DOLPHIN IN EUROPE: RESEARCH AND CONSERVATION

Peter G. H. Evans 1,2

1Sea Watch Foundation, Ewyn y Don, Bull Bay, Amlwch, Isle of Anglesey LL68 9SD, UK 2School of Ocean Sciences, University of Bangor, Menai Bridge, Isle of Anglesey LL59 5AB, UK

STATUS & DISTRIBUTION

The Risso’s dolphin is widely distributed in tropical and temperate seas of both hemispheres (Kruse et al ., 1999; Baird, 2009). It occurs in small numbers along the Atlantic European seaboard from the Northern Isles south to the Iberian Peninsula and east into the Mediterranean Sea, favouring continental slope waters (Evans et al ., 2003; Reid et al ., 2003; Evans, 2008; Bearzi et al ., 2011; see Figure 1).

The major populations in northern European waters occur in the Hebrides but the species is regular also in Shetland & Orkney, and the Irish Sea, as well as around South-west Ireland. It is rare in the North Sea and all but the western end of the English Channel; elsewhere, it is present in North-west France, the southern Bay of Biscay, around the Iberian Peninsula, and in the Mediterranean Sea (Evans et al ., 2003; Reid et al ., 2003; Evans, 2008; Baines & Evans, 2012; Bearzi et al ., 2011; Wall et al ., 2013). In recent years, sightings have extended the range of the species northwards to Norwegian and Faroese waters, although the species has not yet been recorded in Iceland (Kruse et al ., 1999; Figure 1. Main North Atlantic Distribution of Risso’s Bloch et al ., 2012). Dolphin

ABUNDANCE & TRENDS

In the Western North Atlantic, a population estimate of 20,479 (CV=0.59) exists for waters off Eastern USA and 1,589 in the Northern Gulf of Mexico (Waring et al ., 2011), compared with estimates of 29,000 and 2,700 for the two regions respectively ten years earlier (Waring et al ., 2001). No population estimates exist for any region in the Eastern North Atlantic (SCANS-II, 2008; CODA, 2009) or the Mediterranean (Bearzi et al ., 2011). A study in the North Minches, Scotland, identified at least 142 individuals (Atkinson et al ., 1997, 1998). Similarly, at least 345 individuals were photo-identified in the NW Mediterranean between 1990-2004 (Gaspari, 2004; S. Gaspari, pers. comm. ). Aerial surveys in an area of 32,270km 2 east of Spain yielded

10 an abundance estimate of 493 but with very wide confidence limits (CV=0.60) (Gómez de Segura et al ., 2006). There are no obvious population trends for the species in European waters; in the British Isles, numbers visiting the Hebrides and coasts of Wales can vary a great deal between years (Evans, 2008).

POPULATION STRUCTURE

Rather little work has been conducted on population structure in Risso’s dolphins. Gaspari et al . (2007) analysed 51 samples, taken from both stranded animals (n=27) and by biopsy darting of free-living dolphins (n=24), from seven locations around the British Isles (n=18) and six in the Mediterranean (n=33; 27 from the Ligurian Sea). Using minimum-spanning networks, they found that samples from the UK were significantly differentiated from those in the Mediterranean based upon all eight microsatellite loci, and neighbour joining trees based upon the mtDNA control region revealed no shared haplotypes. Haplotype richness was much lower (h=3.0) in the UK population compared with those from the Mediterranean (h=10.75). All three UK haplotypes were closely related to each other. The authors suggest that the reduced genetic diversity of the UK population may be a local founder effect for a population that is at the northern edge of its range.

Significant differences in whistle characteristics (duration, pulse rate and frequencies) between Risso’s dolphins from Scottish and Italian waters have also been demonstrated (Benoldi et al ., 1997, 1999).

HABITAT

Risso’s dolphins show a preference for warm waters (ranging from 7.5-28 oC, but mainly at 15-25 oC, and rarely below 10 oC), generally favouring continental slope waters (Kruse et al., 1999; Anderwald, 2002; Evans, 2008; Wells et al., 2009). In the Eastern Pacific, the species typically occurs seaward of the 180m depth contour, and is seen in coastal areas only where the continental shelf is relatively close to shore (Leatherwood et al ., 1980; Kruse, 1989). In those areas, the depth averaged 1,000m. Steep sections along the edge of the continental shelf are also identified as high-use areas in Eastern USA and the Gulf of Mexico (Hain et al . 1981; Kenney & Winn, 1986, 1987; Baumgartner 1997). In the Mediterranean Sea, highest encounter rates generally occurred also in water depths of 1,000m or more, particularly around the 1,000-1,200m contours (Notarbartolo di Sciara et al ., 1993; Mangion & Gannier, 2002; Cañadas et al ., 2002; Gómez de Segura et al ., 2008; Moulins et al ., 2008). However, in some areas of the NW Mediterranean, the steep upper part of the continental slope occurs close to the coast, and Risso’s dolphins may be found in depths ranging from 200-1,000m (Praca & Gannier, 2007; Azzellino et al ., 2008). By contrast, over the relatively wide continental shelf around the British Isles and Ireland, the species is seen mainly over slopes of 50-100 m depth (Evans et al ., 2003; Reid et al ., 2003; Evans, 2008; Wall et al ., 2013).

ANNUAL CYCLE

Risso’s dolphins were first recorded In the vicinity of the Faroe Islands in 2009 (Bloch et al , 2009). The five sightings since then have all been in either April or August-September (Bloch et al ., 2012). Around the British Isles, although recorded in

11 all months of the year, most sightings occur between May and September, with peak numbers in July-September, particularly in northern Britain (Evans et al ., 2003; Evans, 2008). Risso’s dolphins have been recorded in Irish waters from April to November, with sightings peaking during the summer months; it is largely absent from Irish shelf waters from December to March (Wall et al ., 2013). Risso’s dolphins occur year-round in the Mediterranean, although groups appear to be transient in particular locations even if they return to those sites from year to year, and some evidence for a westerly seasonal (between July and September) movement has been reported in the Ligurian Sea (Airoldi et al ., 2000; Gaspari, 2004; Azzellino et al ., 2008).

In the British Isles, calves may be born in most months of the year, although calving seems to peak between March and July (Evans et al ., 2003; Evans, 2008). An examination of 51 stranded animals in the NW Mediterranean indicated calving between the end of winter and early summer (Raduán et al ., 2007), although the number of calves there peaked in July, whilst the proportion of adults to calves largely remained the same throughout the year (Gaspari, 2004). It is possible that calves are born in most months of the year (CETAP, 1982).

GROUP SIZE AND SOCIAL STRUCTURE

Risso’s dolphins form small to medium-sized pods of 2-50 animals at most European locations where they have been studied, although in some parts of the world, groups may number in the several hundreds or even thousands (Kruse et al ., 1999; Evans, 2008; Bearzi et al ., 2011). Although both smaller and larger groups can be recorded, group size is typically of 6-12 individuals around the British Isles (Evans et al ., 2003; Evans, 2008); 10-25 in Spain (Cañadas & Sagarminaga, 1997; Cañadas et al ., 2005; Gómez de Segura et al ., 2008); and 10-40 in the Ligurian Sea (Airoldi et al ., 2000; Azzellino et al ., 2008; Gaspari et al ., 2008).

Biopsy sampling within Risso’s dolphin groups in the NW Mediterranean yielded limited evidence of genetic similarity, suggesting a fluid social structure (Gaspari, 2004; Gaspari et al. , 2007). On the other hand, re-sightings of individuals associating in the same group over periods of years in the Hebrides, Scotland (Evans, 1987: 173) and the Azores (Hartman et al , 2008), from photo-ID studies, indicate that stable long-term bonds are frequently formed. In the Azores, strong associations between adult males and between adult females were observed, and stable bonds occurred in pair and clusters of 3-12 individuals (Hartman et al ., 2008).

Age and sex segregation of Risso’s dolphin groups has been observed in both Japan (Amano & Miyazaki, 2004) and the Faroe Islands (Bloch et al ., 2012). In the latter case, a school of 21 individuals comprised 71% females, with 67% being mature). Resting females made up 30% of the mature females, and no females were pregnant. The sex ratio of immatures did not differ significantly from 1:1, whereas only 17% of adults were male (Bloch et al ., 2012). There were no old males in the school, nor any weaned immature animals, supporting the hypothesis of young individuals of both sexes leaving the natal group after weaning (Amano & Miyazaki, 2004).

BEHAVIOUR & VOCALISATIONS

Risso’s dolphins are relatively slow swimmers, 4–12 km/h (though usually 6-8 km/h), but when frightened they can speed up to 20–25 km/h (Pilleri & Knuckey, 1969; Podestà et al ., 1997; Kruse et al ., 1999; Evans, 2008). They are usually slightly wary of vessels, only occasionally bow riding (mainly juveniles), and regularly engaging in a variety of surface behaviours (breaching, lob-tailing, spy-hops, tail and flipper slaps) (Kruse et al ., 1999; Evans, 2008).

Following a Risso’s dolphin mass stranding of four adult males and an adult female in July 2005, a rehabilitated male was released in the Gulf of Mexico in February 2006, and its movements and dive behaviour tracked by satellite telemetry (Wells et al ., 2009). The animal travelled more than 3,300km from the Gulf of Mexico to the Atlantic Ocean off Delaware. On average, the dolphin travelled at 7.9km/h (range 0.6- 18.5km/h). The average water depth at recorded locations was 548m (range 3- 2,300m). However, more than 95% of 6,048 dives occurred within 50m of the surface. The deepest dive was 400-500m; the majority of dives >50m depth occurred during dawn and dusk, suggesting a crepuscular pattern for deeper diving. More than 99% of dives lasted less than 6 minutes (mainly between 2-4 minutes) for 2,245 dives that exceeded 30 seconds. The longest dive lasted 9-10 minutes.

In the North Atlantic, Risso’s dolphins are sometimes seen swimming with other cetaceans, including long-finned pilot whales, white-beaked, Atlantic white-sided dolphins, common, striped, and bottlenose dolphins (Shane, 1995b; Atkinson et al., 1997, 1998; Kruse et al., 1999; Evans, 1980, 1987, 2008).

Vocalisations include a variety of clicks, whistles, and pulsed calls. Whistles, rarely heard, range over 2.5-20kHz, usually 8-12kHz, with an average duration of 0.67s, and maximum source level of 170dB re 1 µPa @ 1m (W.A. Watkins, in Evans, 2008). Clicks have a peak frequency of c. 50-65kHz, and last 40-100s (Au, 1993; Madsen et al ., 2004). Click frequencies are broadband from 0.2- >100kHz, with centroid frequencies between 60 and 90kHz, and repetition rates of 4-200/s (Au, 1993; Madsen et al ., 2004). Click-bursts last 0.2-1.5s, with maximum source levels of 202-222dB re 1µPa @ 1m (Au, 1993; Madsen et al , 2004).

Eight different kinds of sounds in three main categories were recognised in Hebridean Risso’s dolphins: clicks in discrete series (echolocation clicks, creaks, grunts) with repetition rates of 37-167 pulses/s; fast sequences of pulses (buzzes, squeaks, squeals, moans) with high repetition rates of 187-3,750 pulses/s, resulting in harmonics; and whistles of 9-13.2kHz (Benoldi et al . 1997, 1998).

Recent descriptions of species-specific spectral characteristics of southern Californian Risso’s dolphin echolocation clicks indicate the presence of alternating peaks and notches within individual clicks such that spectral peaks occur at 22, 25, 31, and 39kHz and spectral notches occur at 20, 28, and 36kHz (Soldevilla et al ., 2008). These allow for species identification by passive acoustic monitoring devices.

Using autonomous acoustic recording packages, Soldevilla et al. (2010) described the geographical, diel, and seasonal patterns of Risso’s dolphn echolocation click activity

13 for six locations in the Southern California Bight, United States, between 2005 and 2007. Risso’s dolphin echolocation click bouts were identified based on their unique spectral characteristics. Click bouts were identified on 739 of 1,959 recording days at all six sites, with the majority occurring at nearshore sites. A significant diel pattern was evident in which both hourly occurrences of click bouts and click rates were higher at night than during the day, suggesting night-time feeding, as indicated also from other studies in the region (Shane, 1995a), and elsewhere (Mussi et al ., 1999). At all nearshore sites, Risso’s dolphin clicks were identified year-round. Seasonal and interannual variabilities in occurrence were high across sites, with peak occurrence in autumn of most years at most sites.

DIET

Risso’s dolphins are largely cephalopod feeders, taking particularly octopus Eledone cirrhosa (N. Atlantic) or Argonauta argo (W. Mediterranean) , cuttlefish Sepia officinalis and various mesopelagic squid Todarodes sagittatus, Loligo forbesi and L. vulgaris, Gonatus spp., Histioteuthis reversa and H. bonnellii, Ancistroteuthis lichtensteinii, Sepiola oweniana , Illex coindetii , members of the family Cranchiidae and pelagic tunicates; they will also occasionally take small fish (e.g. cod Gadus morhua ) (Eggleton, 1905; Tsutsumi, et al., 1961; Mitchell, 1975; Desportes, 1985; Clarke & Pascoe, 1985; Clarke, 1986; Zonfrillo, et al., 1988; Bello & Pulcini, 1989; Podestà & Meotti, 1991; Bello, 1992; Carlini, et al ., 1992; Wurtz, et al., 1992; Cockcroft et al ., 1993; Atkinson, et al ., 1998; Blanco et al ., 2006; Santos et al ., 1994, 1995, 1996; Raga et al ., 2006; Özturk et al ., 2007; Bloch et al ., 2012).

There is some regional (and possibly seasonal) variation in main prey recorded. Around the Faroe Islands in the North Atlantic, Bloch et al . (2012) found 95% of prey (by number) and 94% (by weight) to be the demersal squid Todarodes sagittatus in three Risso’s dolphins in September 2009, and 89% of prey (by number) and 72% (by weight) to be the benthic lesser octopus Eledone cirrhosa in eleven Risso’s dolphins in April 2010. In the latter sample, 10% (by number) and 24% (by weight) of prey was the mesopelagic squid Loligo forbesi . Very few individuals around the British Isles have been examined. But prominent prey items have been Eledone cirrhosa , Todarodes sagittatus , and the oceanic squid Gonatus steenstrupii , and Sepietta oweniana (Zonfrillo et al ., 1988; Clarke & Pascoe, 1985; Santos et al ., 1994). On the Galician coast of NW Spain, where also sample sizes were limited, the two main species were Octopus vulgaris and Loligo forbesi, followed by Eledone cirrhosa (Santos et al ., 1994, 1995, 1996).

In the Mediterranean Sea, the principal prey species observed in stomach contents analysed from samples stranded or by-caught in eastern Spain and the central Mediterranean were the small pelagic octopus Argonauta argo (by number, but not by weight), and the larger mesopelagic squid Todarodes sagittatus , Histioteuthis bonnelli , H. reversa , Ancistroteuthis lichtensteini, and Illex coindetii (Podestà & Meotti, 1991; Bello, 1992; Carlini et al ., 1992; Wurtz, et al., 1992; Blanco et al ., 2006; Raga et al ., 2006). Further east, two by-caught Risso’s dolphins off the Turkish coast had mainly Histioteuthis reversa in their stomachs (Özturk et al ., 2007).

LIFE HISTORY

Our knowledge of life history parameters for Risso’s dolphin is relatively scant. In Japanese waters, the gestation period has been estimated at 13-14 months, and calving interval at 2-4 years (Amano & Miyazaki, 2004), whilst in Spanish waters, mean gestation period was calculated at 13.9 months (Raduán et al ., 2007). Age at sexual maturity is thought to be 8-10 years for females and 10-12 years for males (Amano & Miyazaki, 2004; Baird, 2009). The oldest animal examined in the NW Mediterranean was estimated as 29+ years (Raduán et al ., 2007), 31 years in the Faroe Islands (Bloch et al ., 2012), and 34.5 years in Japan (Amano & Miyazaki, 2004), assuming that one tooth growth layer is equivalent to one year.

With testicular mass representing 3% of the body mass, such large testes suggest sperm competition and a promiscuous mating system, with females mating with multiple males in a single oestrus period (Bloch et al ., 2012). The extensive scarring of adults may also indicate aggressive interactions between males to gain mating access to females (Evans, 1987).

INTERACTIONS WITH HUMANS

Direct takes of Risso’s dolphins occur in various parts of the world, particularly Sri Lanka and Japan (Kruse et al ., 1999; Amano & Miyazaki, 2004), and in Europe, an opportunistic drive fishery has killed 27 animals in two separate incidents in the Faroe Islands (Bloch et al., 2012). Some drive fisheries in Japan occur in response to perceived competition with fisheries (Kruse et al ., 1999).

Risso’s dolphins have been held in aquaria in both Japan and the United States, although relatively uncommonly compared to other dolphin species (Kruse et al ., 1999).

Incidental take through entanglement in fishing gear is widespread although rarely in large numbers. The U.S. East Coast pelagic longline fishery has been particularly responsible for by-catch of this species (Garrison, 2007), and Waring et al. (2007) estimated annual mortality and serious injury for 2000-04 of 46 Risso’s dolphins (CV=0.37), although this has declined to 8 Risso’s dolphins (CV=0.40) for 2005-09, as effort from this fishery (and use of squid bait) declined (Waring et al., 2012). Small numbers are also caught in pelagic drift gillnets, purse seines and pelagic pair trawls, both in the U.S. (Waring et al ., 2012), and elsewhere around the world (e.g. Sri Lanka - Kruse et al ., 1991; Taiwan - Perrin et al., 2005; the Philippines – Dolar, 1995; and Ghana – Van Waerebeek et al ., 2009), where they are often also taken intentionally for food.

In the Mediterranean, most by-catch of Risso’s dolphins is by pelagic drift gillnets, targeting primarily swordfish and tunas (Bearzi et al ., 2011). Although illegal, their use remains widespread (Özturk et al , 2001; Pace et al ., 2008; Cornax & Pardo, 2009). During the early 1990s, mortality of Risso’s dolphins in Italian waters from this fishery was significant and considered probably unsustainable (Di Natale, 1995). Of 100 Risso’s dolphins stranded or rescued along the coast of Italy between 1986 and 2005, 14 were reported to have signs of by-catch (Bearzi et al ., 2011). Risso’s

15 dolphin mortality also has occurred in the Spanish surface longline fishery in the western Mediterranean, with five caught in swordfish gear and two in bluefin tuna gear during 798 fishing operations in a study conducted in 1999 and 2000 (Camiñas & Valeiras, 2001). There are other reports in the Mediterranean of by-catch of the species in bottom-set gillnets and trammel nets deployed in Italy and France (Di Natale & Notarbartolo di Sciara, 1994). In Atlantic France, Spain, and Portugal, bycatch of Risso’s dolphin appears to be low (Morizur et al ., 2011; ICES, 2012).

In the British Isles, between 1995 and 2010, 28 strandings of Risso’s dolphins had post-mortem examinations: 5 were live-strandings, 5 had gas embolisms, 4 died of infectious disease, 4 were thought to be by-caught, 3 died of starvation, 2 of dystocia, one of physical trauma, and for 4 animals, cause of death was not established (Bennett et al , 2000; SAC, 2000; Jepson, 2005; Deaville & Jepson, 2011). This suggests that by-catch in this region is also relatively low, although it should be noted that if populations are small, and occur mainly offshore along the shelf edge, by-catch is probably under-recorded.

Contaminant burdens are poorly known, although total PCB levels were very high (466 and 2061 µg/g wet weight) in the blubber of two animals stranded on the Spanish Mediterranean coast (Corsolini et al ., 1995). DDT levels in one of these animals were also high (670 µg/g wet weight), but much lower in a Welsh specimen, which also had low levels of heavy metals (with the exception of cadmium and zinc) (Law, 1994). Relatively high levels of organochlorine compounds and trace metals (e.g. mercury) have been reported in various Mediterranean studies (see, for example, Marsili & Focardi, 1997; Storelli et al ., 1999; Storelli & Marcotrigiano, 2000; Frodello et al ., 2000; Frodello & Marchand, 2001; Shoham-Frider et al ., 2002; Capelli et al ., 2008), although their impact upon local populations is unknown. Ingestion of plastic and other debris has also been recorded on occasions (Gonzalez et al ., 2000; Shoham-Frider et al ., 2002; Bearzi et al ., 2011).

Increasingly, areas inhabited by Risso’s dolphins are being exposed to noise disturbance from a variety of human activities (recreational craft, shipping, seismic surveys, pile driving, military sonar, etc). Their effects upon Risso’s dolphins are difficult to ascertain, but there have been several cases of negative responses from disturbance by recreational activities in Scotland (P.G.H. Evans, personal observations ), Italy (Miragliuolo et al ., 2004), and the Azores (Visser et al ., 2006; Oudejans et al ., 2007). Gas embolism has been observed in a Risso’s dolphin that stranded in North Wales in 2009 (Deaville & Jepson, 2011). Bubble formation and gas embolisms associated with acute or chronic tissue injury has been linked to exposure to mid-frequency active sonar, as sometimes used in Naval exercises (Fernandez et al., 2005), although no deaths of this particular species have as yet been linked definitively.

Finally, the most likely effects of global warming upon cetaceans in European seas will be changes in species ranges (Evans & Bjørge, 2012). Already, there is some evidence of this for Risso’s dolphin, which in recent years has extended its range northwards to Faroese waters (Bloch et al ., 2012), and is presently regularly recorded in the northern North Sea where cephalopods have become abundant, and where previously it was rare (Evans & Bjørge, 2012; Sea Watch Foundation, unpublished data).

RECOMMENDATIONS

Risso’s dolphins in Europe are uncommon and patchily distributed. Systematic surveys along with habitat modelling should be conducted to better determine hotspots used by the species, and their persistence. Robust population estimates will likely be difficult to obtain by conventional line-transect surveys, and it may be necessary rather to focus attention upon mark-recapture estimates from photo-ID.

Wide-scale surveys of genetic variation throughout the North Atlantic and Mediterranean Sea should be conducted along with the application of complementary techniques such as acoustics and stable isotopes, so as to establish management units across its European range.

Long-term collaborative studies using photo-ID would allow one also to investigate movements, home ranges, social structure, and life history parameters.

Geographical and seasonal variations in diet need to be further investigated using stomach contents, fatty acid and stable isotope analysis.

Finally, there should be a better assessment of the relative importance of different conservation threats on a regional basis, and the possible establishment of marine protected areas for the species.

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Storelli, M.M., Zizzo, N., and Marcotrigiano, G.O. 1999. Heavy metals and methyl mercury in tissues of Risso’s dolphin ( Grampus griseus ) and Cuvier’s beaked whale ( Ziphius cavirostris ) stranded in Italy (south Adriatic Sea). Bulletin of Environmental Contamination & Toxicology , 63, 703-710.

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Wall, D., Murray, C., O’Brien, J., Kavanagh, L., Wilson, C., Ryan, C., Glanville, B., Williams, D., Enlander, I., O’Connor, I., McGrath, D., Whooley, P., and Berrow, S. 2013. Atlas of the Distribution and Relative Abundance of Marine Mammals in Irish offshore Waters: 2005-2011. Irish Whale & Dolphin Group, Kilrush, Co. Clare. 58pp.

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4. CURRENT STATE OF KNOWLEDGE OF THE DISTRIBUTION AND RELATIVE ABUNDANCE OF RISSO’S DOLPHINS ( GRAMPUS GRISEUS ) IN IRISH WATERS.

Dave Wall 1, 2,* , Nick Massett 1, Pádraig Whooley 1, Mick O’Connell 1 and Simon Berrow 1, 2

1Irish Whale and Dolphin Group, Merchants Quay, Kilrush, Co Clare, Ireland 2Marine Biodiversity Research Group, Galway-Mayo Institute of Technology, Dublin Road, Galway, Ireland *Corresponding author; email: [email protected]

INTRODUCTION

Although Risso’s dolphins are regularly recorded in Irish waters, relatively little is known of their distribution, ecology or conservation status. Strandings and casual sightings have been reported to the Irish Whale and Dolphin Group from all coasts and in all months of the year (Berrow et al., 2010). Sightings were most frequently recorded from the south and west coasts, and some evidence of seasonal summer movements has been reported (Wilson and Berrow 2006). Here we present data on Risso’s dolphin distribution from offshore line transect surveys conducted by the Irish Whale and Dolphin Group (IWDG) and the Galway-Mayo Institute of Technology (GMIT), casual and effort-related sightings data and photo-identification data collected between 2005 and 2011 and strandings data collected between 2000 and 2011.

METHODS

Line Transect Surveys

Offshore sightings were collected as part of the IWDG ferry surveys and ship surveys programmes as per the methods described in Wall et al. (2013). Most surveys were conducted by a single surveyor but teams of up to three surveyors were used during IWDG Ferry Surveys.

Non Effort-related Sightings

Casual sightings were collected from members of the public and participating volunteers as part of the IWDG casual sightings and constant effort sightings programmes (Berrow et al., 2010). All casual sightings submitted to the IWDG went through a validation process. Around 15% of sighting records were accompanied by images, which were useful in assisting validation. Where species identification could not be confirmed, sightings were downgraded (e.g. unidentified dolphin / unidentified whale / unidentified beaked whale etc.) according to criteria established for the IWDG’s cetacean sightings database (IWDG 2013). Effort-related sightings collected by land-based volunteers were used in the preparation of distribution and relative abundance maps but were treated the same as non-effort related data and used solely for mapping species’ distribution.

Strandings

Stranded cetaceans were reported to the IWDG from January 2000 to December 2011 from a number of sources but mainly by members of the public and staff of the National Parks and Wildlife Service. A standardized stranding form was produced for recording strandings details. Species identification, length and gender were the basic data required, however additional information on lesions, injuries, presence of fishing net etc. were often reported. Recorders were requested to supply an image with each record, which was essential to validate species identification. Skin samples were taken in some cases for storage in the Irish Cetacean Genetic Tissue Bank which is housed by the National Museum of Ireland, Natural History (Wall 2006).

Photo-Identification

Photo-identification images were opportunistically collected by the IWDG during 29 surveys conducted around the Blasket Islands, Co. Kerry between June 2009 and August 2011. Surveys were conducted in sea state 3 or less from a 6m Rigid Inflatable Boat. 101.5 hours of survey effort were logged, with an average of 3.5 hours per survey, covering an average of 55.6 km per trip.

RESULTS

Sightings and Survey Data

A total of 6,198 hours of offshore line transect survey effort were conducted in Irish and Northern Irish waters, between 2005 and 2011. 27 sightings of Risso’s dolphins were recorded, making them the fifth most frequently recorded dolphin species during the surveys. An additional 242 Risso’s dolphin sightings were recorded by the IWDG Casual Sightings and Effort-Related Sightings schemes in the same time period.

Risso’s dolphins were recorded on a regular but infrequent basis in inshore waters around the entire Irish coast. Their distribution was centered over the Irish Shelf, with highest relative abundances recorded off the southwest and southeast coasts (Figure 1). Sightings data indicated that Risso’s dolphins in Irish waters had a largely coastal distribution and regularly occurred at inshore locations. No sightings were recorded in waters deeper than 1000m.

Risso’s dolphins were recorded in Irish Waters throughout the year, with sightings peaking during spring and early summer. They were largely absent from Irish Shelf waters from December to March (Figure 2). The presence of young calves in some groups indicated that calving occurred in Irish waters.

Strandings

36 Risso’s dolphin strandings were recorded by IWDG from 2005-2011. Strandings peaked in the late summer and autumn (Figure 3) and occurred on the south east, south, west and north coasts, with only a single stranding recorded on the east coast (Figure 4).

Figure 1 . Distribution and relative abundance of Risso’s Dolphins within the Irish EEZ 2005- 2011 (Wall et al., 2013).

Figure 2. Monthly distribution of 242 Risso’s dolphin non-effort related sightings recorded by IWDG between 2005 and 2011 (IWDG 2013).

Figure 3. Monthly distribution of 36 Risso’s dolphin strandings recorded by IWDG between 2000 and 2011 (IWDG 2013).

Figure 4. Distribution of 36 Risso’s dolphin strandings recorded by IWDG between 2000 and 2011 (IWDG 2013).

Photo-Identification

Risso’s dolphins were recorded on 11 of 29 (38%) surveys around the Blasket Islands, Co Kerry, located off the southwest coast of Ireland (Figure 5). Sightings were

28 primarily recorded between Great Blasket Island and Inisvikallane, where a strong current runs between the two islands. Of the 33 animals with well-marked dorsal fins that were stored on the IWDG Photo-ID database (IWDG 2013), 31 were photographed on surveys around the Blasket Islands. There was evidence of site fidelity by Risso’s Dolphins in this area, with one intra-annual and two inter-annual re-sightings. The longest period between re-sightings was 969 days. All re-sightings occurred within the Blasket Islands, with a maximum distance between re-sightings of 10.7 km.

Figure 5. Distribution and group size of Risso’s Dolphin sightings recorded by IWDG boat based surveys of Blasket Islands 2009 – 2011.

DISCUSSION

Risso’s dolphins in Irish waters occurred primarily in continental shelf and inshore habitats. There was no evidence to suggest that they occurred in deep water habitats along the shelf slopes. The distribution of Risso’s dolphins found in this study was in contrast to the reported preference of this species for deep-water slope habitats elsewhere (Shirihai and Jarrett 2006). Why Risso’s in Irish waters exhibit a preference for shelf and inshore waters is not known, however other concentrations of Risso’s dolphins have been reported from adjacent shelf waters in the central Irish Sea (Baines and Evans 2012) and the northwest of Scotland (Weir et al., 2001).

Although the distribution of Risso’s dolphins in the Northeast Atlantic extends north to the Faroe Islands, and all Irish waters lie well within this range, their relative abundance off the north and northwest Irish coasts was low. The reasons for this are not understood, however Wall et al. (2006) noted that the relative abundance of all dolphin species in Irish Shelf waters to the north and northwest of Ireland were significantly lower than elsewhere in the Irish EEZ.

Sightings of Risso’s dolphins are regularly reported from inshore waters and islands of the southeast and southwest coasts. This may indicate a degree of site fidelity by Risso’s dolphins in these areas. Photo-identification data from the Blasket Islands, yielded two inter-annual matches between individuals, with one re-sighting occurring over two years after the initial record. From 2003 to 2006 Risso’s dolphins were regularly recorded off the Dublin and Wicklow coasts of the Irish Sea, between Dún Laoghaire and Greystones (Figure 6). Both before and after this period sighting rates were low for this stretch of coastline, indicating that the local abundance of this species may vary temporally and over extended periods. It is not know what caused the periodic increase in Risso’s dolphins sightings on the Irish east coast during this period or how often such fluctuations in the local abundance of Risso’s dolphins may occur.

Figure 6. Annual numbers of sightings records of Risso’s dolphins recorded from the Dublin and Wicklow coasts by IWDG between 1999 and 2011 (IWDG 2013).

Strandings data indicate that this species occurs year-round in Irish waters, with the sightings data suggesting that Risso’s dolphins may move offshore during the autumn and winter, when inshore sightings decline. The low number of strandings over the past 11 years, coupled with regular sightings records indicates that Risso’s dolphins are regularly occurring but not abundant in Irish waters. Sightings of young calves off the southeast coast indicate that Risso’s dolphins also calve in Irish waters.

CONCLUSIONS

Risso’s dolphins are a regular occurring, consistent and important member of Ireland’s cetacean fauna. Their distribution is patchy with low animal abundance.

The lack of sightings in deep waters beyond the continental shelf is inconsistent with the described habitat preference of Risso’s dolphins in other parts of their range, however similar preference for shallower shelf waters has been described from adjacent UK waters.

Both intra-annual and inter-annual photo-identification matches indicate a degree of site fidelity in some areas. Further photo-identification effort is required in Irish waters, especially off the southeast and southwest coasts.

Genetic studies of Risso’s dolphins in Irish and UK waters may help clarify their population structure.

There is no information available on the diet of Risso’s dolphins in Ireland, nor what their prey species in Irish Shelf waters is. Dietary analysis and radio isotope studies would help elucidate prey species of importance to Risso’s dolphins in continental shelf habitats.

A targeted line-transect survey of the southeast and southwest coasts during late summer and autumn is most likely to enable a robust estimate of Risso’s dolphin local population abundance to be made.

REFERENCES

Baines, M.E. and Evans, P.G.H. 2009. Atlas of the Marine Mammals of Wales. CCW Monitoring Report No. 68. 84pp.

Berrow, S.D., Whooley, P., O’Connell, M. and Wall, D. 2010. Irish Cetacean Review (2000–2009). Irish Whale and Dolphin Group, Kilrush, Co Clare. ISBN 0-9540552-4-1. 60pp.

IWDG. 2013. Irish Whale and Dolphin Group online strandings and sightings databases. Avaliable at: http://www.iwdg.ie/

Shirihai, H. and Jarrett, B. 2006. Whales, dolphins and other marine mammals of the world. Princeton University Press, Princeton. 384pp.

Wall, D., Murray, C., O'Brien, J., Kavanagh, L., Wilson, C., Ryan, C., Glanville, B., Williams, D., Enlander, I., O'Connor, I., McGrath, D., Whooley, P. and Berrow, S. 2013. Atlas of the distribution and relative abundance of marine mammals in Irish offshore waters 2005–2011. Irish whale and Dolphin Group, Merchants Quay, Kilrish, Co Clare. ISBN 0-9540552-7-6.

Wall, D., O’Brien, J., Allen, B.M. and Meade, J. 2006. Summer distribution and relative abundance of cetaceans off the West Coast of Ireland. Biology and Environment: Proceedings of the Royal Irish Academy , 106B, 135–142.

Wall, D. 2006. Irish Cetacean Genetic Tissue Bank. Final Report to the Heritage Council of Ireland. Project reference 14762.

Weir, C.R., Pollock, C., Cronin, C. and Taylor, S. 2001. Cetaceans of the Atlantic Frontier, north and west of Scotland. Continental Shelf Research, 21, 1047–1071.

Wilson, J. with Berrow, S. 2006. A Guide to the Identification of Whales and Dolphins of Ireland. Irish Whale and Dolphin Group, County Clare. ISBN0-9540552-2-5.

5. THE FINE-SCALE HABITAT USE OF RISSO’S DOLPHINS ( GRAMPUS GRISEUS ) OFF BARDSEY ISLAND, CARDIGAN BAY (UK).

Marijke N. de Boer 1,2,3,* , Sonja Eisfeld 3 and Mark P. Simmonds 4,3

1Wageningen IMARES, Institute for Marine Resources and Ecosystem Studies, Postbus 167, 1790 AD Den Burg, The Netherlands 2Wageningen University, Department of Aquatic Ecology & Waterquality, Wageningen, The Netherlands 3WDC, Whale and Dolphin Conservation, Brookfield House, 38 St Paul Street Chippenham, Wiltshire SN15 1LJ United Kingdom (Previous affiliation for MS) 4 Humane Society International, c/o 5 Underwood Street, London N1 7LY, UK. *Corresponding author; email: [email protected]

INTRODUCTION

Information about the habitat use of small cetaceans is essential in order to assess their conservation status. A recent review regarding Risso’s dolphins Grampus griseus (Bearzi et al., 2010) reported that only limited information exist, and for the majority, these are all for waters outside NW Europe (Bearzi et al ., 2010). Large-scale studies within European waters did not yield many sightings and suggest a relatively low abundance for Risso’s dolphins, especially in coastal habitats (e.g. Weir et al., 2001; Cañadas et al., 2002; SCANS-II 2008; Panigada et al., 2009).

Risso’s dolphins have an apparent preference for deep offshore waters and continental slopes, but may inhabit coastal areas around oceanic islands and narrow continental shelves (e.g. Baird 2009; Bearzi et al ., 2010). In UK waters, Risso’s dolphins are recorded year-round and are most common off the Western Isles. They are also present around Orkney and Shetland (close to the species’ known northern limit of distribution), in the Irish Sea, western and southern Ireland and western English Channel, but they are rare in the North Sea (Weir et al., 2001, Reid et al., 2003; Evans et al., 2003; O’Cadhla et al., 2004, Baines and Evans 2009). Based on both opportunistic and dedicated studies, it appears that they are most abundant between May and October, preferring slopes of 50 – 100m depth (Weir et al., 2001; Evans et al., 2003; Reid et al., 2003; Baines and Evans 2009). Risso’s dolphins have been reported in Welsh waters (Baines and Evans 2009) and previous preliminary studies showed the occurrence of this species off Bardsey Island (de Boer et al., 2002). Based on incidental sightings records from Bardsey Island (1976 – 2005), this species occurs here primarily during the months of July to October with additional sightings recorded in April (de Boer 2005). Apart from an area off the West coast of Scotland (1992– 1997; Atkinson et al., 1997; Dolman and Hodgins, this issue ), hardly any studies have taken place in UK waters and current information on the population size and habitat- use is therefore very limited.

The main objectives of this study were (1) to estimate the population size of Risso’s dolphins off Bardsey Island using mark-recapture techniques (De Boer et al ., 2013); and (2) to study habitat-use in relation to fine-scale oceanographic features. This work provides preliminary information on the habitat-use of Risso’s dolphins and will benefit future studies, along with the development of effective conservation measures for this species throughout the region.

MATERIALS AND METHODS

Study Location

Cardigan Bay is a large shallow embayment on the east side of the St. George’s Channel entrance to the semi-enclosed Irish Sea Basin. The Lleyn peninsula in Wales is orientated northeast/southwest and is some 40 km in length, ending in a headland adjacent to deeper water. Bardsey Island (with dimensions of 2.6 km by 1 km) is situated off the tip of the Lleyn Peninsula in the northern part of Cardigan Bay at 52°45.36’N and 004°47.17’W and is separated by Bardsey Sound (approximately 3 km wide; Figure 1). There are strong tidal eddies that exist in the waters surrounding Bardsey Island which have currents of order 3 m s -1 (Elliott et al., 1995).

Figure 1. Cardigan Bay and Bardsey Island located off the Lleyn Peninsula. The observation points (A-D) and ranges are shaded and overlap in places. Drawn isobaths include 10m, 20m, 30m and 50m.

Land-Based Survey Design

A standardised scan sampling system was used, designed to study harbour porpoise (Phocoena phocoena ) during the summer months between 2001 and 2006. A study area (85° to 120°) was slowly scanned using 7 x 50 Nikon binoculars for a period of 10 minutes (de Boer and Simmonds 2002; Pierpoint 2008). Whenever possible, simultaneous observations were carried out from four observation points which varied in height and survey area (Figure 1). A series of 10-minute ‘snapshots’ were produced for each sampling segment, detailing the location of dolphins sighted. Points A and B (both at 17 m height; -5.0 m during spring tide) were situated at the southern tip of the Island, with point B overlooking waters with exposure to prevailing wind and wave action and containing complex bathymetric features, whereas point A overlooked a leeward habitat. The higher points (C–D) were situated at heights of 38m and 60m respectively (-5.0 m during spring tide) and were located on the northern part of the Island. Point C overlooked the waters in Bardsey Sound with strong tidal streams and

33 partly overlapped with the area covered from point B. Point D overlooked the eastern part of the Sound but also partly overlapped with the area covered from point A. The survey area covered from points B and C included two areas of each approximately 90° in size, totaling 170° – 200°.

Observers switched scanning every 10 minutes and also changed platforms every 3 – 4 hours to create a more spread out observer effort. The following information was collected with each sighting: radial distance (using reticule binoculars), bearing (using the built-in compass in the binoculars – these were frequently checked and calibrated), surfacing direction, group-size, presence of calves and juveniles. Distinctive behaviours were noted separately. For each 10-minute scan the Beaufort sea state (0 – 4) and tidal state were recorded. Optolyth telescopes (x30) were used to aid group- size estimation and to distinguish juveniles and calves. All dolphin encounters (whether they were a new sighting for any one day or were re-sightings from previous scans) made during each 10-minute scan were referenced as Scan Sightings (SS).

Data Analysis

We mapped the positions of all sightings (SS) using bearing, radial distance and observation height. The observation ranges were determined for each platform. This was used to estimate the actual survey area with an observation range of <2400 m for the lower platforms and <3600 m for the higher platforms. Land areas and those sea areas not covered were excluded. Because the chance for sighting cetaceans decreases with distance, we estimated that the optimum distance (the area up to which sightings were most reliably seen) for the lower platforms was 2000 m (75% of all sightings occurred up to this distance) and for the higher platforms this was 3000 m (88% of all sightings).

A grid with a resolution of 300 x 300 m was prepared. The chosen grid-size was checked on the accuracy of the distance and angle data in order to ensure that the grid- size (300m) was larger than distance/angle error. It was found that bias in distance estimations or bearing readings became profound (>300m) for the higher platforms when the distance was > 2500 m and for the lower platforms this was 1800 m. Only few sightings occurred at such distances (27 of 297 scan sightings) and when plotting these sighting positions they appeared to be outliers. Nevertheless, the bias in estimated sighting positions is expected to be profound even at shorter distances (especially when errors were made in both distance and bearing measurements). In some cases, this could therefore cause estimated sighting positions to fall into a neighbouring grid cell. However, due to the preliminary character of these analyses, and bearing in mind the low number of grid cells used, it was decided to not make the grid-size larger or increasing the grid-size dependent on distance from the observer. For the total of 607 grid cells (54.61 km 2), the amount of survey effort was calculated (including areas that overlapped). We interpolated mean depth from Acoustic Doppler Current Profiler (ADCP) surveys provided by the University of Bangor (Elliott et al., 1995). Four tidal phases were defined: The High Water (HW) phase was defined as one hour before and after HW and Low Water (LW) was similarly defined. Ebb was defined as 1.5 hours after High Water until 5 hrs after HW; and flood as 5 hrs before HW until 1.5 hrs before HW.

The slope for each grid cell was calculated as ( Dmax – Dmin )/DI where Dmax is the maximum depth in a quadrant, Dmin is the minimum depth in a quadrant and DI the distance in meters between the points of maximum and minimum depth of the quadrant, and expressed in units of meters per km (Cañadas et al., 2002).

Sightings (SS) were entered into a Geographic Information System (GIS) and the abundance (number of dolphins per scan per km -²), for each grid cell within the survey area was calculated. From this, the total abundance for different areas or tidal phases was calculated by adding up the abundance indices for the different grid cells. Using positive scans (those scans during which dolphins were sighted), we studied the relation with oceanographic features: water depth (m), slope (m km -1), tidal state (relative to High Water, HW), current speed (m s -1) and direction. Chi-squared tests were used to investigate whether the observed number of sightings and abundance index differed from expected according to depth and slope. For depth and slope the following classes were defined: depth 0 – 10, 11 – 20, 21 – 30, 31 – 40, 41 – 50, 51 – 60, 61 – 70; and 71 – 80; slope 0 – 10, 11 – 20, 21 – 30, 31 – 40, 41 – 50, 51 – 60. These classes were defined in order to have sufficient sample size in each of the classes, given the restriction in chi-square tests that requires all expected frequencies to exceed 5. A comparison was made between the depth and seabed slopes recorded during flood and ebb tides using Mann-Whitney-U tests.

RESULTS

Abundance and Group-Size

A total of 155 scans (25.83 hrs) were made during which Risso’s dolphins were sighted 297 occasions involving 555 animals (Table 1). The highest number of individual dolphins seen within one scan was 38 but the average was 3.65 (SD 4.84, n = 155). Dolphins were sighted at an average distance of 1849.7m (SD 831.3; range 332.0 - 4649.7m).

Table 1. Summary of effort (scans and hours) and information on Risso’s dolphin Scan Sightings (SS), number of individuals (Ind) during the land-based surveys. Effort SS Year Month Number of scans (Ind) (hrs) 70 2001 Aug – Sept 1378 (229.7) (117) 47 2002 Aug – Sept 943 (157.2) (62) 0 2003 July – Sept 1479 (264.5) (0) 2 2004 July – Sept 1537 (359.0) (4) 158 2005 July – Sept 2641 (440.2) (328) 20 2006 Sept 775 (129.2) (44) Total July – Sept 297 9291 (1548.5) (555)

The abundance was calculated as the number of dolphins (per scan/km 2) sighted in each of the grid cells. Figure 2 shows the core areas where dolphin abundance exceeded 0.25 dolphins (per scan/km 2). There are two main ‘core areas’ with relatively high dolphin abundance (>0.25): Box 1 (to the west and northwest of the Island) and Box 2 (to the north of the Island within Bardsey Sound). In addition, two smaller areas to the east of the island also showed high dolphin abundance. The total abundance in Box 1 was 35.39 dolphins and in Box 2 this was 15.86 dolphins.

Figure 2. Abundance of Risso’s dolphins (dolphins per scan km -2) for each grid cell. The position of scan sightings are shown as circles with the size of each circle indicating the number of individuals.

Figure 3. Grid cells with mean group-size for Risso’s dolphins. The positions of calves (dotted dots) and juveniles (crossed dots) are also shown. 36

Proportion of positive scans and number of sightings per tidal state (relative to High Water)

0.14 45 40 0.12 35 0.10 30 0.08 25

0.06 20 (SS)

number) 15 0.04 tidal state/total state/total tidal 10 (positive scans per scans per (positive

Proportion of scans of Proportion 0.02 5 sightings Number of 0.00 0 Proportion of scans HW HW-6 HW-5 HW-5 HW-4 HW-3 HW-2 HW-1 HW+1 HW+2 HW+3 HW+4 HW+5 HW+6 Number if Tidal state sightings (SS)

Figure 4. Proportion of positive scans (positive scans per tidal state/total number of positive scans) and proportion of scan sightings (SS per tidal state/total SS). Tidal state is presented as the number of hours +/- High Water (HW).

Figure 5. Risso’s dolphin abundance (dolphins per scan km -2) during flood (A) and ebb (B) in the core areas (black dotted Boxes) and in relation to tidal eddies (grey dotted Boxes) during flood (C) and ebb (D). Arrows indicate the direction and strength of the currents where the size of the arrow (left bottom corner) corresponds to 1m s -1. Information regarding currents and eddies were derived from Neil (2008).

The mean group size per scan for Risso’s dolphins averaged 2.11 (SD 1.34, n = 96, range 1-6) with the highest group size measured in Bardsey Sound (Figure 5). All calves (except for one) were found to the west of the Island (Box 1), whereas juveniles were observed all around the island (Figure 3).

Tidal Cycle

Risso’s dolphins sightings appeared to be correlated with the tidal state with significantly more sightings made during flood ( χ2 = 112.27, df = 3, p<0.001). The highest proportion of positive scans was made during HW-3.5 hrs, at the peak of the flood phase, during which also the majority of sightings were made (Figure 4). During ebb the highest proportion of positive scans was made at HW+5 hrs, with the majority of sightings made at HW+4.5 hrs (Figure 4).

During flood, the dolphins were particularly abundant to the west/northwest of the Island (Box 1) and sightings were also made to the southeast and in Bardsey Sound. During ebb they were mostly abundant to the north of the Island (Box 2) with additional sightings to the East (Figure 5a and b). The total abundance in Box 1 during flood was 32.26 dolphins and during ebb this was 11.89 dolphins.

Proportion of Risso's dolphins in relation to depth (m) and Slope (m km-1)

0.400 0.350 0.300 0.250 Depth (m) 0.200 Slope (m km-1) 0.150 (SS/effort) 0.100 0.050 Proportion of dolphins dolphins of Proportion 0.000 0 _ 10 11 _ 20 21 _ 30 31 _ 40 41 _ 50 51 _ 60 61 _ 70 Depth (m) & Slope Category (m km-1)

Figure 6. Proportion of Risso’s dolphins (scan sightings per unit effort) in relation to depth (m) and slope (m km -1).

Depth and Slope

The majority of dolphins were sighted in waters between 30–40 m (59%) with a mean water depth of 32.72 m (SD 8.73, n = 280, range 13.60–57.40 m) and a mean slope of 23.79 m km -1 (SD 9.68, n = 291, range 4.72–42.45 m km -1; Figure 6). Dolphin abundance was not distributed uniformly through all classes of depth ( χ2 = 35.43, df = 5, p<<0.001) and slope ( χ2 = 17.57, df = 4, p=0.001). The mean depth for those grid cells where dolphins occurred was 32.22 m during flood (SD 8.38, n =176) and 30.47 m during ebb (SD 12.47, n = 39). The mean slope for those grid cells where dolphins 38 occurred during flood was 22.29m km -1 (SD 9.03, n = 175) and during ebb this was 28.40 m km -1 (SD 9.31, n = 51). There was no significant difference to preferred depth class 30–40 m during ebb or flood. However, there was a significant preference for steeper slopes during ebb ( U = 2819.5, n = 226, p<0.0001).

DISCUSSION

Risso’s dolphins were mainly sighted in waters with a mean depth class of 30–40 m. However, this was expected as most of the available habitat is 30-40 m depth. The dolphins were also observed in waters as shallow as 7 m. Similar observations with Risso’s occurring in shallow waters were reported off NW Scotland (<30 m; Gill et al., 1997) and off the Canary Islands (<20 m; Ruiz et al ., 2011). Risso’s dolphins are usually found in deeper waters. Across the Mediterranean Sea, they are sighted in waters around 1000m depth (Cañadas et al., 2002; Gannier 2005; Bearzi et al., 2010) and in less deep waters of the continental slope (mean depth 638m; Praca and Gannier 2007). Risso’s dolphins off the Azores are more frequently sighted in waters of 600 m (Pereira 2008), whilst most dolphin sightings off Scotland occurred in <200 m depth (Weir et al., 2001). In this study, the dolphins preferred those areas with slopes of 20 – 30m km -1 and this is less-steep than reported for deeper waters. For example, Baumgartner (1997) defined the slope class of 41.6 to 402.5 m 1.1 km -1 as highly preferred in offshore waters (Gulf of Mexico). In deep waters of the Mediterranean Sea, Cañadas et al. (2002) reported a preference for slopes exceeding 40 m km -1. Other studies (Mediterranean and Azores) also confirm the preference for steep slopes (Gannier 2005; Praca and Gannier 2007; Azzellino et al., 2008; van Geel et al., 2008; Moulins et al., 2008; Airoldi et al., 2010, Bearzi et al., 2010).

Our observations indicate that relatively shallow coastal waters (up to 50 m) with consequently less-steep slopes may also offer suitable foraging habitats for Risso’s dolphins. The majority of calves were recorded in Box 1 where lower current speeds may offer a preferred habitat for nursery groups compared to areas with fast flowing waters (Bardsey Sound) where the risk for mother and calves to become separated is greater. Similar findings have been documented for porpoise calves in Welsh waters (Pierpoint 2008). There have been few studies of cetaceans foraging in island/headland wakes. Johnston et al. (2005a) reported on fin whales ( Balaenoptera physalus ) and minke whales ( B. acutorostrata ) that exploited a tidally driven island system in the Bay of Fundy. Pierpoint (2008) reported on foraging porpoises in a headland/island system in Wales. Similarly, porpoise densities were found to be significantly greater during flood in an island wake system (Johnston et al., 2005b). In the Moray Firth (Scotland), bottlenose dolphins showed fine-scale foraging movements within a narrow channel (Bailey and Thompson 2010). In Alaska the abundance of humpback whales ( Megaptera novaeangliae) appeared to be related to tidal influences near headland wake systems (Chenoweth et al. , 2011). Like any other headland/island system, Bardsey has residual eddies that are formed on either side of the island (northwest and southeast eddies) during flood and ebb (Elliott et al., 1995; Neil et al., 2007). At fine spatial scales, small-scale eddies and fronts appear to enhance the primary productivity and it is recognised that these features may concentrate prey (e.g. Simard et al., 2002; Zamon 2003). It seems therefore likely that the areas of upwelling and eddies in Bardsey waters can influence the availability of nutrients, retention of plankton and aggregation of fish that may attract prey (Baumgartner 1997; Kruse et al., 1999; Yen et al., 2004).

The diet of Risso’s dolphins consists primarily of cephalopods (Würtz et al., 1992; Clarke 1996; Kruse et al., 1999). Risso’s have been observed predating on octopus (Octopus vulgaris ) off the Canary Islands in shallow waters (<20 m; Ruiz et al ., 2011) and off Scotland they predominantly take lesser octopus ( Eledone cirrhosa ; Atkinson and Gill 1996; Santos et al., 1994). The lesser octopus was also found in the stomachs of Risso’s stranded in Wales (Merrett 1998) and southern England (Clarke and Pasco 1985). The lesser octopus is especially common inshore in the summer (July – September) during the peak spawning period and further offshore in October – December (Boyle 1986). It is therefore likely that the dolphins in Bardsey waters were also targeting lesser octopus. It is worth noting that the presence of local beds of horse mussel ( Modiolus modiolus ) close to Bardsey may attract squid and octopus (Wharam and Simmonds 2008).

The area where dolphins were most abundant during the flood phase (Box 1) corresponded to a western eddy formed during flood (Figure 5c, d). The high current speeds in Bardsey waters indicate that large volumes of water are transported along and into the eddy during flood and then slow down and circulate, effectively concentrating prey into the eddy region and forming a suitable foraging location for dolphins during flood. The ebb-eddy, which is approximately positioned over a shallow sand bank to the Southeast (Neill 2008), probably does not offer suitable foraging conditions for Risso’s dolphins. The dolphins favoured the Sound during ebb and where large upwellings (slick domes of water on the surface) were consistently seen. In addition, the narrowness of Bardsey Sound may concentrate prey. Marine predators can then focus their foraging efforts on such locations to improve efficiency and reduce energetic costs (Bailey and Thompson 2010).

Many large marine predators use vast areas of the ocean, but typically concentrate their activities in smaller, localised biological hotspots for periods of time (Johnston et al., 2005b). The tidal eddies in Bardsey waters enhance the foraging efficiency for Risso’s dolphins by aggregating their prey in a predictable manner during different tidal phases in localised areas. Such static bathymetric features may form the initial basis for identifying potentially critical habitats for Risso’s dolphins within relatively shallow coastal systems.

ACKNOWLEDGEMENTS

Research in this remote area has only been achieved through the dedicated efforts of many WDC staff and volunteers. Special thanks go to Jo and Trevor Clark, Sarah Dolman, Nicola Hodgins, David Janiger, Simon Keith, Rob Lott, Steve Stansfield (Bardsey Island Bird Observatory) and Joanna Wharam. We sincerely thank Simon Neill (University of Bangor) for providing the ADCP data, the BBC Wildlife Fund and the Countryside Council for Wales for their support.

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6. LAND AND BOAT-BASED OBSERVATIONS OF RISSO’S DOLPHINS OFF NORTH-EAST ISLE OF LEWIS, SCOTLAND FROM 2010 TO 2012

Sarah J. Dolman 1, Nicola K. Hodgins 1 and Alison Gill 2

1 Whale and Dolphin Conservation (WDC), Brookfield House, 38 St Paul Street, Chippenham, Wiltshire SN15 1LJ. email: [email protected] 2 Intelligent Ocean. P.O Box 1218, Kings Lynn, Norfolk. PE32 1XR. email: [email protected]

INTRODUCTION

The Outer Hebrides in north-west Scotland, and particularly the North-east Isle of Lewis, have been shown to have significant concentrations of Risso's dolphins (Paxton et al., 2011; Weir et al., 2001; Pollock et al ., 2000; Atkinson et al ., 1998). Sightings indicate possible year-round residency but are most frequent over the summer and autumn months, with clear peaks in numbers in August and September (Pollock et al ., 2000; Atkinson et al ., 1998). The suggestion that at least a part of this population is resident here is supported by studies off the north-east of Lewis that have repeatedly resighted individuals (Atkinson et al ., 1998; this study). A photo-ID study conducted over two years identified 142 individuals, with at least 52 animals resighted between years (Atkinson et al ., 1998).

Juveniles have been sighted in this region between March and November (Pollock et al ., 2000; this study). Off the north-east coast of Lewis, whole groups that comprised exclusively of sub-adults or juveniles were noted on several occasions, and a group consisting of eight females, each with a calf, has also been observed (Atkinson et al ., 1998).

High sightings rates are also reported for the rest of the western part of the Hebrides during the summer (Reid et al., 2003) and there may be further areas of importance in these less studied waters. There are generally few Risso's dolphin data available in more offshore waters but sightings occur mostly during autumn and winter and are concentrated along the continental slope (Reid et al. , 2003; Pollock et al. , 2000). Sightings offshore are too few to suggest particular areas of importance, but show that the species also inhabits deep-water areas north-west of Scotland.

Between 1990 and 2009, there were 206 confirmed strandings of Risso’s dolphins around the UK, Ireland and Isle of Man (Dolman et al. , 2010). A high incidence of these strandings occurred around Lewis. Post-mortems were conducted on 31 of these animals. Where known, cause of death was anthropogenic in some cases, including bycatch (5), physical trauma (1) and entanglement (1).

Analysis of stomach contents of Risso’s dolphins stranded in Scotland since 1992 reveals that Eledone cirrhosa is its most important prey species. Movement of Risso’s dolphins may be linked to prey availability. Preliminary analysis and modelling revealed a positive association between areas of presence for the two species, a relationship which will now be tested on a larger data set (Pierce et al ., 2012).

An estimated 86% of Europe's Risso's dolphins are found in UK waters making it an important stronghold for this species (UK BAP, 2008). Scottish Government have listed Risso’s dolphins as Priority Marine Features, warranting marine protected areas (MPAs). More generally, all cetaceans are listed as Annex IV on the EU Habitats Directive, therefore requiring ‘strict protection’ throughout their range. There is not enough information available about the species to know how they are faring and no population-level information is available on trends in abundance in the UK. Information on the distributional range of the Risso’s dolphin found in the UK population(s) are also limited. Nonetheless, Risso’s dolphins are clearly a distinctive feature of the Isle of Lewis marine fauna.

METHODS

Study Area

The study area comprised the coastal waters of north-east Isle of Lewis in north-west Scotland, located in the Minch, from the Shiant Islands in the south to Tolsta Head in the north (Figure 1). The water depth drops steeply to 100 metres close to shore.

Figure 1 . Field study location on the Eye Peninsula, Isle of Lewis, NW Scotland (100 metre depth contour shown).

Land-Based Data

Data were collected from land-based viewing platforms using an established scan sampling protocol (Pierpoint et al., 1998). Following this method, an observer slowly scanned across a predefined sector of sea using 7x50 reticuled binoculars with built-in compass. Observers took it in turn to each complete scan. Observations were conducted continuously in sea state 3 or less, with 1 m swell or less and in good

45 visibility. Teams of two observers were stationed at each platform throughout the survey when weather conditions allowed. Within the team, one member acted as observer and the other as data logger.

All large marine animals were recorded. All cetaceans detected were recorded to lowest taxonomic level possible and only confirmed species sightings were used in this analysis. Environmental data including sea state, swell height and visibility were gathered every 10 min or when conditions had changed. For each observation the species, number of animals (including presence of juveniles and calves), time, bearing and distance to animal, direction of travel, behaviour and association with seabirds were recorded.

Animals were classified as adults, juveniles and calves where possible, using the following criteria: individuals that appeared fully grown were recorded as ‘adult’; individuals obviously smaller than fully grown (75% adult size) were defined as ‘juveniles’; and very small animals closely associated with an adult, were classified as ‘calves’.

Boat-Based Data

Vessel based surveys were conducted from a different vessel in each year. In 2010, the survey vessel was MV Puffin , approximately 5m motor boat. In 2011, the survey vessel was MV Fish n’ Trips, a 6 m motor boat and in 2012 MV Fish n’ Trips was a 6.5m Rigid Inflatable Boat (RIB). Surveys were opportunistic, depending upon suitable weather and availability. The vessel route was determined at the start of each day, based on prevailing weather conditions. The vessel position was continually recorded at 1-minute intervals using a handheld Garmin GMAP 76CSx GPS. Observers were stationed on the port and starboard side of the boat watching for cetaceans on either side of the vessel (from the beam to the bow of the vessel).

During boat-based surveys, animals were approached carefully and appropriately, at slow speed and from the side in order to obtain photo-identification images. Photo images were taken under Scottish Natural Heritage (SNH) license numbers 10991 and 13371. All images of identifiable Risso’s dolphins were contributed to a catalogue of animals created for this project. Photographs were taken of individual animals encountered with the aim of collecting images of both the left and right side of the dorsal fin. Once suitable photographs were obtained the vessel moved on with the intention of minimising time spent with the animals and therefore minimising potential disturbance.

Images were primarily taken using a Canon 7D digital SLR camera with a Canon EF 100- 400mm f4.5-5.6L IS USM lens and occasionally using Canon 30D and 40D digital SLR cameras fitted with a Canon EF 70-300 f/4-5.6L IS lens. Images were graded with a quality rating based on the focus, angle, and size of the fin within the image (1 = poor to 3 = excellent, following Parsons, 2003). Photographs of grades 2 and 3 were primarily used to identify and catalogue individuals using standard methods (Würsig & Jefferson, 1990). However, some grade 1 images were used when highly distinctive animals could be recognised (see Weir et al ., 2008).

Static Acoustic Data

CPODs are static acoustic devices that detect toothed whales, dolphins and porpoises by identifying the trains of echo-location sounds they produce. Resulting data on the number of click trains recorded in each minute can be used to determine the presence or absence of target species in different time periods, providing a fine-scale technique for assessing longterm variability in the occurrence of certain cetacean species in specific sites.

Passive acoustic data were collected from three CPODs deployed between May – September 2011 (at Bayble, Braighe and Kebock Head) and from four CPODs deployed between June – October 2012 (at Broad Bay, Bayble, Braighe and Loch Erisort). The CPODs record porpoise and dolphin vocalisations and enable us to understand presence, and help to assess which areas and which times of year are important for the animals. The CPODs were deployed under licence, obtained from Marine Scotland

Risso’s Dolphin Group Sizes

Risso’s dolphin group sizes from this study were compared with surveys conducted in 1995 and 1996.

RESULTS

Land-Based Data

Between 2010 and 2012, six marine mammal species, basking sharks and a sunfish were positively identified from land-based surveys. Observations are recorded in Table 1.

Table 1. On-effort land-based observations from Tiumpan Head, Isle of Lewis between 2010 and 2012 Species Groups Individuals Fin/Sei whale, Balaenoptera borealis/physalus 1 1 Minke whale, Balaenoptera acutorostrata 52 59 Risso’s dolphin, Grampus griseus 14 55 Common dolphin, Delphinus delphis 7 80 Bottlenose dolphin, Tursiops truncatus 4 25 Harbour porpoise, Phocoena phocoena 48 91 Unidentified dolphin 8 72 Grey seal, Halichoerus grypus 4 4 Basking shark, Cetorhinus maximus 19 19 Sunfish, Mola mola 1 1 Total 158 407

Land-based sightings and individuals per unit effort (60 min) were calculated for Risso’s dolphins (Table 2).

Table 2 . Land-based sightings and individuals per unit effort (60 min) for Risso’s dolphins Tiumpan Head, Isle of Lewis between 2010 and 2012 per 60 mins Year Groups Individuals SPUE IPUE 2010 5 54 0.0017 0.0186 2011 3 7 0.0030 0.0071 2012 2 6 0.0022 0.0065 Total

A total of 1,130 suitable photo-ID images of Risso’s dolphins were collected from land between 2010 and 2012. Image quality was largely dependent on the distance of the animals to shore as well as both sea and lighting conditions. The value of images taken when animals were +200m from the shore is negligible and these images were only used to confirm a resight of an already identified and well-marked individual. Less than 20% of images taken from land were of grade 3 quality. Between 2010 and 2012, as a result of land based observations, 12 animals were added to the catalogue, including three mother-calf pairs, and an additional 18 animals already in the catalogue were resighted within and between subsequent years.

Boat-Based Data

29 days, or parts thereof, were spent at sea, surveying from the Shiant Islands in the south to Tolsta Head in the north. Marine mammal basking sharks and two sun fish observations are presented (Table 3).

Table 3. Boat-based observations during WDCS Isle of Lewis survey between 2010- 2012 Species Groups Individuals Minke whale, Balaenoptera acutorostrata 1 1 Risso's dolphin, Grampus griseus 13 75 Common dolphin, Delphinus delphis 6 107 Bottlenose dolphin, Tursiops truncatus 4 29 Harbour porpoise, Phocoena phocoena 60 265 Grey seal, Halichoerus grypus 21 38 Harbour seal, Phoca vitulina 1 1 Seal 1 1 Basking shark, Cetorhinus maximus 7 7 Sun fish, Mola mola 2 2 Unidentified dolphins 2 7 Total 118 523

A total of 2,959 suitable photo-ID images of Risso’s dolphins were collected during these surveys. A total of 55 animals have been positively identified in the catalogue, 75% of which have images of both left side dorsal (LSD) and right side dorsal (RSD). Photo-identifications have been made of eight mother-calf pairs. There have also been seven resightings between the three years of data.

One animal, accompanied by a calf and photographed by the authors in 2011 has been confirmed as the same animal photographed in the same area by Caroline Weir in 2005. The animal displayed massive trauma to her dorsal fin in the 2005 photograph making her easily recognisable.

Table 4. POD deployment details during WDCS Isle of Lewis survey 2011, including Dolphin detections per hour (DPH) per day POD location Start End days total DPH per day Kebock Head 08/06/2011 24/09/2011 108d 0hr 17m 0 (4) Loch Erisort 10/12/2011 28/03/2012 109d 7hr 11m 0 (16) 23/03/2012 07/06/2012 74d 20hr 11m 0 (0) 20/06/2012 07/10/2012 108d 22h 19m 0 (8) Braighe 11/06/2011 25/09/2011 106d 19hr 29m 0 (7) 13/06/2012 22/09/2012 101d 10hr 53m 0 (50) Bayble 01/06/2011 26/09/2011 117d 20hr 21m 2 (109) 07/06/2012 05/10/2012 119d 9h 42m 1 (99) Broad Bay 30/06/2012 04/10/2012 96d 5h 55m 0 (18)

Table 5. A comparison of Risso’s dolphin group sizes during land and boat-based surveys in 2010-2012 compared with surveys conducted in 1995 and 1996 Average group Boat Year size min max 1995 13.3 5 35 1996 14.1 1 100 2010 8.9 1 14 2011 4 3 5 2012 1 1 1 Land 1995 9.3 2 20 1996 7.3 1 20 2010 6.8 1 15 2011 2 1 3 2012 3 2 4

Static Acoustic Data

Frequency of dolphin detections per hour per day (DPH per day) or the detection rate on each CPOD is presented in Table 5. Both dolphins and porpoises were detected on all CPODs during their deployments, but the number of days on which they were detected varied considerably from site to site.

It is not currently possible to use click characteristics to determine which species of dolphins have been detected on the PODs, and given the number of species encountered visually in the survey area, it is likely that detections represent different species. Further analysis will include effort to differentiate Risso’s dolphin recordings from those of other dolphin species found in the region.

Risso’s Dolphin Group Sizes

An initial comparison of group sizes observed during land and boat-based surveys from this study were compared with land and boat-based surveys previously conducted in 1995 and 1996 (Table 5).

CONCLUSIONS & DISCUSSION

Generally poor weather conditions during our field seasons restricted the amount of field data that could be collected. Eight Risso’s dolphin calves were observed, including one with foetal folds. A female with a distinctive, deformed dorsal fin that was previously observed and photographed in the vicinity in 2005 (Caroline Weir, pers. obs.) was observed in 2011 with a young calf. These initial results demonstrate use of the area over many years and strengthen the evidence for residence of Risso’s dolphins in this area and use of the area with very young calves. More detailed photo- identification analysis is underway. Our data demonstrate the diversity of marine species encountered off the north-east Isle of Lewis, where six marine mammal species were positively identified, as well as basking sharks and two ocean sunfish.

In Scottish territorial waters, potential threats to cetaceans include military activities occurring on the west coast offshore exercise range, oil and gas exploration and production, widespread fisheries and extensive coastal aquaculture. With lower human population than other regions, overall the Western Isles are not subject to such high levels of development and vessel traffic, although development is moderate in places. The area supports a moderate marine ecotourism industry, with the potential to cause disturbance. Marine renewable energy (wind, wave and tidal) is likely to be important off the west coast in future years, with unknown consequences on marine mammals at present but potentially including collision risk and habitat loss. In this region, the combined impacts of these activities are probably of most concern.

Evidence of anthropogenic threats to Risso’s dolphins comes from stranded individuals (Institute of Zoology data, unpublished) and indicates that a variety of impacts occur, although the scale is unknown (Dolman et al ., 2010). Causes of death include fisheries interactions, such as bycatch and entanglement, and gas embolism, likely to be a result of noise pollution (Jepson et al ., 2003). Risso’s dolphins are taken in directed hunts in the Faroe Islands and in other parts of the world. It is unknown if the Risso’s dolphins studied off Lewis travel between this study site and the Faroes Islands. Given that Risso’s dolphins are approaching the northern limit of their range in UK waters, climate change may influence their distribution in Scottish waters either directly or indirectly via changes in their cephalopod prey. The predicted conservation implication of range changes as a result of increasing water temperatures has been suggested as favourable for Risso’s dolphins (MacLeod, 2009). A lack of knowledge between the predator and prey linkages is an impediment to the protection of this species but is currently investigated by Aberdeen University (Pierce et al., 2012).

Local fishermen reported that sightings and group sizes of Risso’s dolphins had reduced in recent decades. Comparing group sizes from data collected during surveys conducted in 1995 and 1996 to our own field surveys appear to support this incidental observation, and warrant further investigation. Although the differences could be due to observers counting techniques, during both periods slightly higher counts were

50 made during boat surveys compared to land surveys and so this seems unlikely. Sightings were much lower in 2011 and 2012 than in previous years were data were collected.

Our understanding of and the implication of disturbance of Risso’s dolphins are little understood. With plans to increase aquaculture farms, marine renewable energy and other activities in areas of known habitat, it becomes more important than ever to close this data gap. Marine Spatial Planning and Marine Protected Areas are both mechanisms that can, and should, assist in the effective protection of cetaceans. This is particularly true in areas of critical habitat such as those identified around the Isle of Lewis. The Marine (Scotland) Act 2010 has provided the Scottish government with a duty to undertake marine spatial planning - a regionally-based approach towards the cumulative management of all users of the marine environment, including designation of Marine Protected Areas (MPAs) that should contribute towards a well-managed and ecologically-coherent network to meet international targets by 2012. MPAs potentially represent an important mechanism for the protection of cetaceans (Hoyt, 2011). The identification of areas used for important life processes such as feeding, breeding and raising young, can be protected explicitly and transparently through spatial measures. The Scottish MPA guidelines include Risso’s dolphins, minke whales and white-beaked dolphins as Priority Marine Features (PMFs).

Finally, data should continue to be collected towards a longer term understanding of the animals’ needs and adequate protection in this area. Specifically, data are required to understand abundance, distribution limits and long term trends in the population, seasonal movements, diet and the fine scale habitat of prey, as well as reproductive parameters and mortality rates. Baseline data are important to ensure appropriate management decisions to maintain ‘strict protection’ of European Protected Species, including Risso’s dolphins. Such data are most valuable when used in association with known potential impacts to manage disturbance.

ACKNOWLEDGEMENTS

The support of DEFRA, BBC Wildlife Fund and Elite Couriers enabled this field project. We would like to thank Scottish Natural Heritage for granting WDC a photo- id license and Marine Scotland for an acoustic license. We would like to thank everyone who made the surveys possible, and especially Lewis at Hebrides Fish n’ Trips, our Tiumpan Head Shorewatch team and the SNH Stornoway office. Thanks to Caroline Weir and Charlie Phillips for the use of their photo-IDs. Thanks to Caroline Weir for her suggestions to a draft of this extended abstract.

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7. STUDY OF RESIDENCY PATTERNS, HOME RANGES AND MOVEMENTS OF RISSO’S DOLPHINS ( GRAMPUS GRISEUS , CUVIER, 1812) IN THE WESTERN LIGURIAN SEA.

Elisabetta Remonato 1* , Andrea Aimi 2 and Sabina Airoldi 1

1Tethys Research Institute, Viale G.B. Gadio 2, 20121 Milan, Italy 2Micromys, Loc. Comano 33, 38077 Comano Terme, Italy Corresponding author; email: [email protected]

INTRODUCTION

Although Risso’s dolphins have been studied in various parts of the world, many aspects of their ecology, including their ranging patterns, are still unclear (Bearzi et al ., 2011). The study of the spatial behaviour of individuals in a population, in particular understanding their use of the space at different times and the causes behind that, is extremely important for furthering understanding of the broader ecology of the species (Stevick et al ., 2002).

The home range (HR) of an animal is defined as “the area traversed by the individual in its normal activities of food gathering, mating and caring for young” (Burt 1943). From the dimensions and characteristics of the HR it is possible to understand the residency level and site fidelity of an individual. It is also possible to understand the territoriality and various other aspects of the interactions with con-specifics as well as characteristics of the social structure of the population (Ostfeld 1990) and biological aspects such as the diet (Swihart et al ., 1988).

The residency pattern indicates the tendency of an individual to frequent a geographical area and to return over time (Wells et al ., 1987, Wells 1991, White and Garrot 1990). Animals that can perform long-range movements have the ability to exploit large and diverse food resources and to move with changes in their availability. This is in contrast to those animals whose movements are more constrained and are therefore more dependent on the distribution and abundance of prey in a specific location.

The movement patterns greatly affect the social structure of cetacean populations. They are a significant factor determining the quantity and quality of relations between con-specifics and influencing the social and cultural evolution of a given population (Rendell and Whitehead 2001). The study of animal movements not only provides information on the ecology of individuals but also on the gene flow between other groups or populations living in surrounding areas.

In the Mediterranean Sea Risso’s dolphins occur mainly in continental slope waters, especially in steeper regions, near the coast or in the presence of submarine mountains or canyons (Azzellino et al ., 2008). Most sightings occur during the summer in the north western part of the basin within 10 km of the coast. Less frequently Risso’s dolphins have also been sighted in pelagic waters (Di Méglio et al ., 1999, Azzellino et al ., 2008).

This work analyses the data collected in the western Ligurian Sea with the aims of identifying animals with a high degree of residency, determining their HR and analysing their short-term and long-term movements.

MATERIALS AND METHODS

Study Area

The study area is situated in the western Ligurian Sea, in an area which is part of the Pelagos Sanctuary for marine mammals, and covers about 25,000 km 2. It includes the waters between S. Raphael (43° 25’ N, 6° 50’ E), Cape Mele (43° 55’ N, 8° 10’E), Cape Corso (43° 00’ N, 9° 25’ E) and Girolata (42° 20’ N, 8° 35’ E) on the island of Corsica. The majority of the effort was concentrated in the core research area between the Lerin islands (43° 19’ N, 7° 12’ E) and Imperia (43° 48’ N, 8° 1’ E) and within 60 km of the coast (Figure 1).

Figure 1. Western Mediterranean Sea: Pelagos Sanctuary and TRI’s study area (core research area in green).

Data Collection

Photo-identification and position data were collected through ad libitum surveys over a period of twenty years (1990-2009). Data gathered within the study area by whale watching boats between 1996 and 2000 were also included. Sighting and effort data (i.e. position, species, group size, course, speed, sea state, visibility, etc.) were recorded on paper forms and in a digital database using data logging software (IFAW LOGGER 2000). All the sighting positions and the photo-identification images available, whether recorded in positive or negative effort, were included in the analysis. Photographs collected prior to 2003 were taken with a Minolta 700si SLR

Dinax 35 mm camera equipped with an auto-focus telephoto 80-200 mm APO (maximum brightness 2.8 f). The films used were professional Fuji Provia 100 ASA. The resulting slides were digitised using a scanner. From 2004 digital SLR cameras were used, starting with a Nikon D100 with an auto-focus telephoto 80-200 mm (maximum brightness 2.8 f) and then a Canon EOS 350D and a Canon EOS 1000D, both with an auto-focus telephoto 70-200 mm (maximum brightness 2.8 f).

Data Analysis

All of the photo-identification images were assessed following the TRI’s protocol (TRI_Photo-identification Handbook, unpublished) and only those of sufficient photographic quality and individual distinctiveness were included in the analysis. All photo-identification results were confirmed by at least two experienced researchers. The age class of each animal was assessed in the field by estimating the body size and observing the behaviour of immature individuals in relation to adults (Mann and Smuts 1999, Shane et al ., 1986).

Four age classes were considered: a) newborns - individuals shorter than half the length of an adult and swimming in close and constant association with an adult; b) calves - individuals about half the length of an adult and in evident association with an adult but less closely than newborns; c) juveniles - individuals about two-thirds the length of an adult and swimming usually in association with an adult but sometimes independently; d) adults - individuals on average 3.5 meters long and with independent behaviour. The classifications made during the surveys were subsequently confirmed or corrected during the analysis of the photographs.

Pods of individuals that were seen only once or twice within a single season and then never seen again were considered transient pods. Risso’s dolphins belonging to transient pods were considered transient individuals. Females were defined as individuals sighted in close association with a newborn or calf a minimum of three times. Males were defined as individuals sighted in five or more seasons and never seen in close association with an immature individual.

The residency patterns of each individual were determined by analysing the sighting frequencies of all the animals. Resident individuals were then identified using an iterative bootstrap approach which examined the mean and variance of the extent of the HR for varying sample size (Hooge et al ., 2000).

The estimate of the HR of each individual was obtained through the use of the Kernel method (Worton 1989). This estimator is based on probability “kernels” which represent the likelihood of the animal’s presence in regions around each point location (Worton 1989, Kernohan et al ., 2001). In particular the fixed Kernel method (KHR) was used rather than the adaptive Kernel because it is more robust when the number of samples is less than 50 (Kernohan et al ., 2001, Seaman et al ., 1999, Seaman and Powell 1996, Worton 1989). The HR was defined as the area with 95% UD (95% probability of presence at a point within the HR) and the core areas within the HR were defined as the areas with 50% UD (50% probability of being present at a point within the core areas).

The non-probabilistic Minimum Convex Polygon (MCP, Mohr 1947) method was also used, mainly for comparative purposes. The MCP method estimates the HR by calculating the smallest convex polygon containing all of the observed positions.

Both methods can be adversely affected by the inclusion of outliers. Without identifying and removing outliers the estimated HR can contain areas never used by the animals. Removing a certain percentage of points (such as 5%) can mitigate outlier effects (Hooge et al ., 2000). In this work the harmonic mean Outlier Removal method (White and Garrott 1990) available in Arcview® 3.2 was applied for both methods.

Using the above methods the HR was calculated for: each resident individual on its own; all the resident male individuals combined; all the resident female individuals combined; all the resident individuals combined.

The movements of the resident individuals were analysed using the Arcview® 3.2 Animal Movements Analyst extension. The linear distance and the time between consecutive sightings of the same animal were calculated. The mean distances for the male individuals were compared with those for the females. In particular the distances covered in the short-term (1, 2 and 3 days) were studied and used to estimate the mean daily travel speed.

RESULTS

A total of 194,265 km were covered in positive or negative effort over a period of 2,343 days at sea (Figure 2a) resulting in 175 Risso’s dolphin sightings of either individuals or groups (Figure 2b) and averaging 8.75 sightings per year. There were a minimum of 254 and a maximum of 276 photo-identifications (188 both sides, 88 right side, 66 left side). The overall encounter rate was one Risso’s dolphin sighting (single individual or group) per 1,042 km of navigation. Transient individuals, newborns and calves were excluded from the analysis. Juveniles with fewer than three sightings were also excluded resulting in a total of 205 individuals analysed.

Residency Patterns

Analysis revealed that 9.7% ( n= 20) of the photo-identified individuals ( n= 205) have a high degree of residency within the study area with 11 or more resightings. These animals were considered “resident” (Figure 3). 42.4% of the individuals were sighted only once or twice while 47.9% of the individuals were resighted between 2 and 10 times (Figure 4). These animals were considered “episodic” and “occasional” respectively (Table 1). 22.9% of the individuals were sighted in five or more separate years. The mean number of resightings for the resident individuals was 15.1 (SD= 3.55, n= 20). No significant differences were found between the sighting frequencies of females and males (Mann-Whitney U(13,7)= 37.5, p= 0.535). The mean time between consecutive sightings of the same individual was 319 days (median= 287, SD= 432.279, n= 283).

Figure 2 (a,b). Map of the routes surveyed (a) and the Risso’s dolphin sightings (b) between 1990 and 2009.

Table 1. Residency patterns of all animals based on number of sightings. Number of Animals Number of Sightings Residency Pattern 87 (42.4%) 1-2 Episodic 98 (47.9%) 3-11 Occasional 20 (9.7%) 12-23 Resident

Figure 3. Resighting frequency of resident individuals ( n≥ 11).

Figure 4. Resighting frequency of non-resident individuals ( n≤ 10).

The mean time interval between the first and last sighting (First-Last Sighting Interval – FLSI) of the resident individuals was 13.35 years (SD= 3.066, n= 20), the longest was 19 years (individual “Macchia”) and the shortest was 8 years (individual “Andrea”).

Home Ranges of the Resident Individuals

The HR of each of the 20 resident individuals was calculated through the Minimum Convex Polygon (MCP) and the fixed-Kernel (KHR) methods resulting in significantly different distributions for each animal. The mean extent of the HR as calculated by the MCP method covered 860.4 km 2 and by the KHR method covered 2,444.7 km 2 at 95% UD (SD= 332.60 km 2) and 513.5 km 2 at 50% UD which constitutes the core areas (SD= 419.30 km 2). HR as calculated by the MCP and KHR 95% UD methods were significantly different (Wilcoxon T< 0.001, p< 0.0001, n= 20) and weakly correlated (Spearman R= 0.454, R 2= 0.206, p= 0.0453, n= 20). For each resident individual all of the core areas were within 50 and 2,200 m of depth (mean= 1,125 m) and there was considerable overlap between individuals. As calculated by the MCP method the mean extent of the HR of the male individuals covered 785.8 km 2 (SD= 252.96, n= 13) and of the female individuals covered 999.0 km 2 (SD= 434.56, n= 7). The mean extent of the HR as calculated by the KHR 95% method was much larger than that calculated by the MCP method both for the male (mean= 2,349.8, SD= 1,095.84, n= 13) and female individuals (mean= 2,621.0, DS= 1,308.39, n= 7). The mean extent of the core areas was 477.7 km 2 (SD= 412.4, min= 91.5, max= 1,728.6, n= 13) for the male and 579.8 km 2 (DS= 456.74, min= 149.9, max= 1,244.7, n= 7) for the female individuals. There was no significant difference in the HR for males and females (MCP: M-W U(13,7)= 33.0, p= 0.351, n= 20; KHR 95%: M-W U(13,7)= 42.0, p= 0.817, n= 20; KHR 50%: M-W U(13,7)= 42.0, p= 0.817, n= 20). The results of the HR and core areas of the resident individuals as calculated for the female individuals combined, the male individuals combined and all the resident individuals combined are shown in Table 2 and in Figure 5a, b and c.

Movements of the Resident Individuals

Most routes were parallel to the coastline along bathymetric lines between 200 and 1,600 m of depth (Figure 6). The mean distance between consecutive sightings was 18.10 km. The minimum distance between consecutive sightings was 4.52 km over 1 day and the maximum was 113.07 km over 92 days (SD= 19.971 km, n= 129). 73.6% of the distances between consecutive sightings were less than 20 km and 2.3% of the distances were greater than 100 km. The mean travel speed was 5.5 km/day (calculated using measurements up to 3 days between consecutive sightings).

Table 2 . HR and core areas of the resident individuals. KHR KHR KHR KHR KHR 50% MCP 50% Sex N Fix 95% 75% 50% max (km 2) min (km 2) (km 2) (km 2) Depth Depth F 7 56 2,248.6 2,616.0 756.7 229.4 100 1,600 M 13 69 2,643.9 2,773.6 932.2 294.5 100 1,600 F + M 20 79 2,185.3 2,352.2 727.2 216.3 100 1,400

Figure 5 (a, b, c). HR and core areas of resident females (a, n= 7), resident males (b, n= 13) and all residents (c, n= 20) as calculated by the MCP and KHR methods.

Figure 6. HR as calculated by the KHR 95% UD method and movements between consecutive sightings of resident individuals.

Figure 7 shows the minimum and maximum distances travelled with respect to the number of days elapsed between consecutive sightings. As can be seen from the linear trend lines both the minimum and maximum distances travelled tend to increase gradually with increasing time between sightings.

Figure 8 shows the strong tendency of the mean distance between consecutive sightings to be proportional to the time interval between sightings for up to 3 days, as is evident by the high value of the R 2 correlation coefficient (0.8479). If greater time intervals are included in the analysis the correlation decreases rapidly.

Figure 7. Minimum (blue squares) and maximum (red dots) distances between consecutive sightings of resident individuals.

Figure 8. Mean distance between consecutive sightings of resident individuals for up to 3 days.

DISCUSSION

The mean number of Risso’s dolphin sightings per year (8.75) is relatively low compared with those of other species observed in the study area throughout the duration of the study period, such as striped dolphins ( Stenella coeruleoalba , 146.10 sightings/year) and fin whales ( Balaenoptera physalus , 40.75 sightings/year) (Airoldi et al ., 2009, Azzellino et al ., 2012). This could indicate a disproportionately low abundance of the species which might be due to insufficient resources or inter-specific competition with other species that also prefer the slope habitat, such as the sperm whale ( Physeter macrocephalus , Azzellino et al ., 2008, Azzellino et al ., 2012).

Analysis identified three different residency patterns: a) episodic - animals using the area for short periods; b) occasional - animals using the study area as the far edge of their HR; c) resident - animals using the study area intensively.

The Mann-Whitney U test conducted on males and females showed no significant difference in their respective residency patterns. This suggests an absence of ethological differences between the sexes able to affect the chances of being spotted. However, it cannot be ruled out that a bias in the sex identification method could have affected the results of this analysis, therefore the homogeneity in the spatial distribution of the two sexes should be confirmed by further observations based on sounder methods of sex identification (e.g. karyotype determination).

The highest First-Last Sighting Interval (FLSI) resulting from the analysis was 19 years for an individual named "Macchia". Since this individual was an adult at the time of his first sighting, and in literature the youngest known adult was 2.5 years old (Bearzi et al ., 2011), it is estimated that “Macchia” was at least 21.5 years old when last sighted in June 2009. The oldest Risso’s dolphin ever reported in literature was a female found in the Pacific Ocean which had an estimated age of 38 years (Taylor et al ., 2007). In Italy the oldest individual of this species found stranded was estimated to be 29 years old (Bearzi et al ., 2011). “Macchia” may be regarded as the oldest studied Risso’s dolphin living in the Mediterranean Sea.

Due to the low number of sightings of each individual it was possible to study the HR during the entire study period (1990-2009) but not for individual years. The HR estimates obtained using the KHR 95% method were significantly larger (up to 5.65 times) than those obtained using the MCP method. This may be due to the low number of available samples, when the number of samples is lower than 20 the KHR method tends to overestimate the extent of the HR and the MCP method tends to underestimate it (Seaman et al ., 1999). This may explain why the Spearman rank correlation for the results obtained using the two methods was very weak (R 2= 0.206). Despite the limitations arising from the low number of sightings available, analysis identified the presence of core areas (centres of activity) which provide an indication of the habitat preferences within the HR, particularly in relation to bathymetry and distance from the coastline. It is important to understand that the identification of core areas could potentially be a product of the modelling and biased research effort rather than indicate areas of real importance for the animals. Further investigations are required to determine the significance of these areas to the animals. This work constitutes the first study of Risso’s dolphins’ HR therefore no previous results are available for comparison.

Analysis found considerable overlap between the core areas of the different individuals, which had a mean depth of 1,125 m (min= 50 m, max= 2,200 m) and frequently coincide with waters where the slope gradient is steeper. This finding is compatible with results published by Azzellino et al . (2008) but also suggests an occasional use of coastal and pelagic waters. Risso's dolphin sightings have been reported in shallow waters by Praca and Gannier (2008) and in pelagic waters by Di Méglio et al . (1999) and Azzellino et al . (2008). It is likely that these animals use different areas of their HR in different ways depending on their current activity (e.g. travelling, feeding or caring for offspring). This might be the reason why in some cases the KHR method showed the presence of centres of activity in two or three disconnected areas several km apart from each other. No significant difference was found in the HR of the different sexes. This is in contrast with results found for other mammals, including cetaceans, where often the two sexes have very different spatial behaviours (Wells et al ., 1987, Flores and Bazzalo 2004, Tufto et al ., 1996). Larger individuals require more food resources and this is often reflected in a larger extent of the HR for male or females depending on the species. In Risso's dolphins the size of males and females is not significantly different which may explain the absence of a significant difference in the extent of their HR, or alternatively this could be due to the abundance of resources in the study area throughout the summer. In general, however, the extent of the HR of an animal or group of animals is never determined by a single factor, but results from the combination of several variables working simultaneously (Ford 1983, McLoughlin and Ferguson 2000). It is therefore possible that considering additional variables which were not included in this study, such as the associations between individuals (Hartman et al ., 2008, Gaspari 2004), may facilitate a more accurate modelling of the HR.

The core area of all of the resident individuals combined is in an area of between 100 and 1,400 m of depth and is located above submarine canyons. These results are consistent with previous studies conducted on the habitat and distribution of Risso's dolphins in the Ligurian Sea (Azzellino et al ., 2008, David and Di Méglio 1999) and other areas of the western Mediterranean (Cañadas et al ., 2002, Gómez de Segura et al ., 2008). Due to the phenomenon of up-welling, which is more common around submarine canyons, nutrients rise from the bottom of the sea triggering high primary productivity which attracts various organisms in the food web (David and Beaubrun 2001, McGehee et al ., 2004) including the mesopelagic cephalopods which are the preferred prey of Risso's dolphins (Bearzi et al ., 2011). The results obtained are therefore consistent with the observation that the core areas usually contain a greater availability of resources (Ford 1983). Although the estimated HR might be considered reasonable approximations perpendicular to the coastline, they may be less accurate parallel to the coastline (to the east and to the west). This is because the actual HR may exceed the study area and also the research effort was not uniform throughout the study area, tending to concentrate in the waters surrounding Sanremo, the operating base of the project. These factors could be mitigated by expanding the study area (e.g. through collaboration with other research organisations) and compensating for the non-uniform research effort during the analysis. Previous studies based on photo- identification data of Risso's dolphins in the western Mediterranean (David and Di Méglio 1999, Polo et al ., 2009) were carried out in the Gulf of Lion and in the Gulf of Genoa. These two areas are located to the west and the east of the TRI study area respectively. Polo et al . (2009) compared the photo-identified animals in the Gulf of Lion with those of the Gulf of Genoa and found 15 positive matches. It is therefore

64 reasonable to hypothesise that the area investigated in this work may just be part of the actual area used by the studied Risso’s dolphins.

Analysis of the movements revealed a mean distance between consecutive sightings of 18.10 km. Most of the distances were shorter than 20 km and only a few exceeded 100 km. This suggests that the most frequent resightings correspond to individuals that remained in the area for just a few days. Long-distance movements may represent travel between known areas or be exploratory in nature. Behaviours of this type, in particular looking for new feeding areas, have been documented in other marine mammals such as pinnipeds (Stevick et al ., 2002) and bottlenose dolphins ( Tursiops truncatus ) where it has been hypothesised that groups of animals are able to travel large distances simply following a school of fish while hunting (Silva et al ., 2008). No significant differences were found in the movements of males and females. The mean distance travelled is strongly correlated to the time between consecutive sightings for short resighting periods (1-3 days) and rapidly becomes less correlated for greater periods. This result may in part be due to the inability of the researchers to follow the animals outside the study area. The underlying trends in the directions of the movements of the resident animals revealed a preference for routes parallel to the coastline which is consistent with the average shape of their estimated HR. This is also in accordance with the bathymetry they are understood to prefer which runs parallel to the coastline in this area (i.e. 500-1000 m, Azzellino et al ., 2008). The short-term mean travel speed was found to be 5.5 km/day (calculated for periods up to 3 days). This estimate is similar to that found by David and Di Méglio (1999) which ranged from 3.7 to 4.2 km/day.

Studies of the spatial and temporal distributions of cetaceans can be particularly difficult due to the sparse spatial and temporal sampling densities which arise from the potentially large areas used by the animals and the often relatively low number of sightings. The results found in this work, although interesting, are clearly limited to the study area. In order to improve the biological knowledge and inform conservation efforts it is necessary to comprehensively assess the wider spatial distribution of the Risso’s dolphin population in the Mediterranean Sea. This should be done by increasing the sample size and the extent of the study area through collaboration with other organisations to combine all of the available data.

AKNOWLEDGEMENTS

We are grateful to all of the researchers and assistants who participated in the collection of the data used in this work and all of the students who helped with the photo-identification analysis. Special thanks goes to the skippers of the R/V Pelagos Roberto Raineri and Paolo Pinto. Thank you to David Wrobel, Dr. Arianna Azzellino, Dr. Simone Panigada and Viridiana Jimenez for their help in many aspects of the work. Thank you to Joan Gonzalvo for reviewing this manuscript. Data were collected with the software “Logger 2000” which is developed by the International Fund for Animal Welfare (IFAW). Thank you to Portosole harbour, Sanremo, for logistical support and hospitality.

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8. SHOW ME YOUR BODY AND I TELL YOU HOW OLD YOU ARE: A NON- INVASIVE METHOD TO DEFINE 6 LIFE HISTORY- CLASSES IN RISSO’S DOLPHINS ( GRAMPUS GRISEUS ) USING AN IDENTIFIED TRIAL POPULATION IN THE ATLANTIC.

Karin L. Hartman 1,2,* , Anja Wittich 2 and José Manuel N. Azevedo 1

1 Department of Biology, University of the Azores, Rua Mãe de Deus 13, 9501-801, Ponta Delgada, Azores, Portugal 2Nova Atlantis Foundation, Risso's Dolphin Research Center, Rua Dr. Freitas Pimentel 11, 9930-309, Santa Cruz das Ribeiras, Lajes do Pico, Azores, Portugal Corresponding author; email: [email protected]

INTRODUCTION

Kruse (1989): “The ability to estimate the ages of animals is a critically important tool in the study of mammalian life history. Knowledge of growth rates, age at sexual maturity and longevity are needed to assess the health and productivity of populations. Ages of animals can be determined by knowing birth dates of individuals and following them throughout life.”

However, determining age for cetaceans is a difficult task. Current methods used include body length, teeth, ear plugs, bones and even eye lenses (e.g. Klevezal and Klejnenberg 1967; Lockyer 1972; George et al., 1999; Fearnbach et al., 2011). The standard delphinid technique of estimating age is obtained by counting dental growth layer groups (GLGs). Each layering group represent one year (e.g. Tursiops truncatus , Hohn 1980; Globicephala macrorhynchus and G. melas , Kasuya and Matsui 1984; and Stenella longirostris , Myrick et al., 1986). All these are invasive methods and cannot be applied to live animals restricting data collection considerably (exception of body length).

In marine mammals other proxies besides the GLGs technique have been used to determine age classes of populations, mainly analyzing variations over time in skin colour. Narwhals ( Monodon mococeros ), e.g., lighten with age (Silverman 1979, Hay 1984, Hay and Mansfield 1989). Auger-Méthé et al. (2010) investigated the amount of white marks on the skin of narwhals as a proxy for age but no relationship was found. For spotted dolphins ( Stenella frontalis ) four phases of spotting, subdivided into early and late stages, have been correlated with age (Herzing 1997). By closely monitoring individuals over the years, the development of the color patterns and the durations of the phases were used to categorize dolphins by age class. The ontogenetic development of color patterns was also used in a long term study in Indian Ocean bottlenose dolphin ( Tursiops aduncus ) (Ross and Cockroft 1990, Smolker et al., 1992). For other marine mammals such as grey seals, ( Halichoerus grypus ), the natural pelage markings on the head and neck tend to darken with age and seem to progress more quickly in the first years of life. Overall females tend to be lighter in color than males (Vincent et al., 2001).

Grampus Teeth Function and Skin Coloration

The skin of cetaceans is more sensitive to cuts and scratches than the skin of other mammals, since they are lacking natural protection or fur. Numerous factors, such as accidents, parasites, predators and intraspecific tooth rakes, leave their marks on the skin (McCann 1974; Lockyer and Morris 1990; MacLeod 1998). Scarring from teeth tends to be long and parallel (Heyning 1984). The amount of unpigmented scarring varies widely among cetacean species but is mainly observed in odontocetes. This scarring is extremely visible in Risso's dolphins, accumulate primarily on the animals' dorsal and lateral surfaces (Wursig and Jefferson 1990; Kruse 1999; MacLeod 1998; Hartman et al., 2008) and is also observed in other species such as the narwhal, the sperm whale ( Physeter macrocephalus ), and several beaked whales species (MacLeod 1998). The skin of the Risso’s dolphin changes during different life stages: calves are born silvery grey, turn dark brown or black as sub adult and may become almost white as older adult (Lien and Katona 1990; Hartman et al., 2008; Bearzi 2010). This unique discoloration process is mainly caused by the teeth of other Risso’s dolphins during social interactions, leaving linear marks on the skin and the dorsal fin. These scars turn white, which is possibly caused by reduced skin pigmentation in this species (MacLeod 1998). Through evolution, some cetacean species became specialized cephalopods hunters, a diet that does not require teeth (Clarke 1986). The teeth in Risso's dolphins are reduced to only three to seven pairs at the front of the lower jaw (Clarke 1986; Lien and Katona 1990) and present in all age classes and for both sexes (Wursig and Jefferson 1990; MacLeod 1998). The function of teeth in teuthophagous cetaceans is believed to be a weapon. This is the case for Risso’s dolphins. MacLeod (1998) found evidence that un-pigmented scars have an important function for this species’: it may function as an indicator of ‘male quality' or male dominance and is therefore used to avoid risks of escalating aggressive encounters between unevenly matched individuals. Results from a social structure study in the Azores indicate that stable cluster pods, consist of whiter animals who are assumable males (Hartman et al., 2008).

Life History at Present: Age and Body Length in Risso’s Dolphin

Risso’s dolphins (male and females) can reach over 30 years of age by counting GLGs. (Kruse 1999; Taylor et al., 2007; Bloch 2012). The oldest reproducing female found known to date was determined to be 38 years old (Taylor et al., 2007). Risso’s dolphins reach a body length of about 3 to 4 meters long with no significant sexual size dimorphism (Kruse et al., 1999; Bearzi 2010). Whitehead and Mann (2000) report a median birth length of 1.3m, a median adult length of 3.3m and a mean length at female sexual maturity of 2.8m. The literature reviewed concerning morphological data of Risso´s dolphins suggest that morphological differences in body sizes occur between populations (Ross 1984; Kruse et al., 1999; Amano and Miyazaki 2004; Bloch 2012).

Objectives

Hartman et al. (2008) defined 5 scarification classes for different stages of scarification on the dorsal fin (from “very limited” to “very severe”) using the percentage of visible white scars versus the density of dark skin. The unpigmented scars on the dorsal fin of resighted individuals in the Azores remained stable for at

70 least 3 years leaving a unique opportunity here to investigate the scarring processes in more detail using other parts of the skin on the body. In summary it is ethically impossible to know the correct age of wild living Risso’s dolphins. Therefore it is certainly an essential tool to determine the age class composition of a population, in order to understand and interpret fundamental aspects of marine mammal biology. The objective of this paper is to present a new non-intrusive and inexpensive method to classify six life history stages in Risso’s dolphins: from newborn calf to old-adult. We propose an age-class indicator model using the scarification patterns and the species unique discoloration process. We developed two methods and tested these among 52 rankers to examine if our proposed methods could be applied by anybody and if they would conform with our age class model. We also investigated the possible differences in the scarification patterns between genders. We used a long- term followed identified population of Risso’s dolphins in the Azores to set up our test methods and report our present results.

MATERIALS AND METHODS

Study Area and Field Observations

This study was carried out in the coastal waters (approximately 0-6 kilometers offshore) around Pico Island, in an area of approximately 540 km 2, belonging to the Azores Archipelago.

Boat-based surveys were conducted yearly from 2000 till 2012. Observations were carried out up to sea state ≤ 4 (Douglass scale, ds). Risso’s dolphins were located with guidance from 12 fixed look-out posts situated around the island, with the main lookout located in Santa Cruz das Ribeiras (Figure 1). At the start of every ocean observation environmental conditions, such as wind force, wind direction, sea state, visibility and GPS co-ordinates, were recorded.

Figure 1. Detailed map of survey area (Pico Island).

Main Database

Risso’s dolphins were individually identified using distinctive characteristics like notches, nicks, amputations and the unique scarification pattern on the dorsal fin (See Hartman et al. 2008 for a detailed overview of the photo-identification methods used). Identifications photographs were taken from May 2000 till June 2012, during dedicated ocean surveys, using analogue (Minolta X700, 70-200 mm 36/400 ISO slide films) and SRL digital camera’s (Nikon D70-D200-D300, 70-300 mm zoom lens).

Age Classes and Gender Determination

For the determination of six life history based-age classes the skin of the frontal part of the back (behind the blowhole and in front of the dorsal fin) was photographed and used as main measure area (Figure 2). The fact that the dolphin needs to surface in order to breath, creates good recapturing opportunities, since it will lift up its head, meanwhile showing the frontal back part.

On average we used high quality pictures: 100% sharp, taken approximately between 10 - 20 meters from the dolphin, showing a clear view of the back part, head and dorsal fin area, hardly no interferences of water or sunlight glimmerings on the measurable parts. Occasionally we used medium quality pictures defined as not 100% sharp, some interference of water and or sunlight, not all parts 100% visible.

Figure 2. Example of a picture of the frontal area of the back, after the blowhole and before the dorsal fin, which was used for age class determination.

Trial Phase

At the start of this study we tried to develop a precise standard to quantify the amount of visible scars (white) versus the original skin (black). We used several computer- assisted methods in order to define a correct % but these methods failed (Figure 3). After our quality selection, pictures needed to be adjusted to grey tones when using Adobe Photoshop software.

Additionally the clearness and contrast tool was used in order to create the best possible balance between the inner species scarring (white parts) versus the original skin (black parts). Furthermore, we were unable to create a solution to remove natural irregularities appearing on our pictures like areas with glimmering sunlight, and droplets of water from waves or blows. When pictures were converted to black and white these areas were treated as “white area”- counting as a natural scar and therefore intensively influencing the measurement process, showing false values of

72 scarifications percentages. Although we had promising results in the older classes, we run into trouble when analyzing the material of the younger animals. Their skin wasn’t always dark brown or black but also greyish, hence the original and unscarrified skin was quantified as “white areas”, again giving false values of scarification. Since we had to deal with our free-ranging and natural obtained photo material we looked for a method were we would not adjust the pictures after a secure selection of the picture quality.

Figure 3. Examples of computer assisted manipulation of pictures to quantify scars

Life History Scar Type Determination Model: Scarification Guide

First, six classes were defined: calf, juvenile, sub-adult, adult-1, (female/male) adult-2 (marbled-female/male) and adult -3 white-female/male) (Figure 4).

Figure 4. Age classes, using six scarification categories .

For the development of a life history-age class determination model, photographs of long term resighted individuals were selected using data from 2000 until 2012. From several individuals, the age was known since they were followed as newborn calves. In our model this is the case for the life cycle “calf” and the “calf to sub-adult”. Examples for the following life cycles were determined by comparing photographs of individuals over time with overlapping scarification patterns (Figure 5).

The scarification processes were compared among animals categorized in the same age class. Since the coloration processes were documented in detail a subdivision of 12 sub stages was made and used (Figure 7).

Furthermore, an overview of observed morphological characteristics per age class was summarized for this observed population. Behavioral aspects were determined using unpublished data (Hartman). Social structure characteristics were defined after Hartman et al. (2008 Error! Reference source not found. ).

Gender Determination

Males and females were distinguished whenever possible. Adults accompanied by a calf were defined as females. A calf was defined when observed in “calf position” next to the mother (Mann and Smuts 1999). Males were defined based on the long- term absence of accompanying calves, corroborated by behavioral and genital area observations, severity of scarification patterns on the skin, robust body build and the appearance in stable cluster pods (Hartman et al. 2008). Molecular sexing from an ongoing unpublished study confirmed observational determinations in most cases (Hartman unpublished data).

Figure 5. Age Class Determination Model, based on six scarification stages and 6 long term followed individual Risso’s dolphins.

Table 1. Characteristics of coloration and scarification in Azorean) Risso’s dolphins. Picture Age Scarification Behavioural Age Size Colouration Number class pattern description New -born calves have a Overall typical yellow unscratched Surfacing in 0-4 1- snout and 6-10 and pale- typical calf 1 Calf years 2.2 m vertical foetal greyish position next to folds covering (original) the mother. their central skin. body. From 4 -6 years, Pale-greyish to Very few and dispersed from Juv- 4-6 2.2- 2 dark brown thin linear mother. May enile years 3 m skin. marks visible. be observed in close proximity to natal group. Living in typical Several single bachelor Overall dark layered linear groups, mixed Sub- 6-12 2.5- brown to black 3 marks visible, gender Adult years 3.3 m skin. Dark mostly possible . Not appearance. original skin. well connected at social structure level. Clear first First covered Nursing layered layer of white females use scarification Adult scarified skin. crèche system. 10-18 3.2- pattern 4 stage Mixed Males may years 4 m visible, 1 appearance of form very original skin black and stable cluster clearly white. pods. visible. Nursing Marbled to females use Adult marbled-white Almost no crèche system. 15-25 3.2- 5 stage skin. Overall original skin Males may years 4 m 2 whitish visible. form very appearance. stable cluster pods. Nursing Double females use Overall white layered skin Adult crèche system. >25 3.2- skin. Overall scarification 6 stage Males may years 4 m whitish pattern on 3 form very appearance. whole body stable cluster visible. pods.

Body-Sizes

In this study, all body sizes were estimated using subjective personal estimations, based on 13 years of observation effort and experience. Average body size for calves and juveniles were estimated by comparing their length with the estimated body size of the accompanying adult. The size of a newborn calf normally excites about 40% of the size of an adult (Whitehead and Mann 2000). (One observation was made of a premature calf of approximately 1 meter of length (Hartman unpublished data.) For the other age classes’ size was determined by eye, also using the length of the two working platforms (a 4.2 m. semi ridge and 7.2 m. fiberglass boat) to estimate body length of adult individuals swimming a side of it.

Pictures Used for Rater Test Set (“By Eye” and “Ruler”)

An even distribution of different age class and gender classes was sought of as well as a sample size which would lead to robust results. For each method 120 pictures were chosen which consisted of 12 different age/gender classes ( Table 1). There were a minimal number of duplicate pictures between the two test sets but as all pictures were in random order recognition was deemed minimal. The data set does not allow for gender identification prior age class A1 and we hypothesize that a difference in scarring is not likely to occur prior reaching adulthood. There was an emphasis on the adult age classes as this new distinction was a main focus of this test. We split the adult classes up by gender as we hypotheses that males will be more heavily scared in contrast to females at the same age. Animals of unknown gender were also included.

Table 1. Number of pictures in Test Set split up by age/gender class # of Age class (gender) pictures 10 Calves (gender unknown) 10 Juveniles (gender unknown) 10 Sub -Adults (gender unknown) 10 A1 (gender unknown) 10 A2 (gender unknown) 10 A3 (gender unknown) 10 A1 (female) 10 A2 (female) 10 A3 (female) 10 A1 (male) 10 A2 (male) 10 A3 (male) 120 TOTAL

The majority of the calves, juveniles and sub adults were closely monitored animals, for which the age was known. Females categorized as an Adult1 were nursing their first calf and were followed since sub-adulthood. Females categorized as an Adult2 had at least 2-3 confirmed calves during the study period, while females in the Adult 3 class were substantial “whiter” in appearance than the Adult2 females, mostly still nursing with at least 2 confirmed nursing periods, and/or consorting younger females displaying assumable post-fertile and allo -maternal behavior. Male Adult 1– were

77 followed since sub-adulthood , 2 and 3 individuals were classified by gender based on molecular sexing (Hartman unpublished data), long term followed behavior and cluster pod formation.

Since our main goal was to test whether these proposed classes could be determined by others, two groups of rankers were invited to test the two methodologies. The first group consisted of biologists which were mainly people who work with cetaceans. The second group consisted of people from the general public . This distinction was made in order to recognize if prior knowledge, expertise or training are required to establish this method.

By Eye Classification

For the Bye Eye classification method we ranked the overall scarification patterns of the back part using additional features like the coloration of the head, the scarification on the dorsal fin and the saddle patch (Figure 6).

Figure 6. Body areas used in for “By Eye” method as described in Table 1, 1: dorsal fin; 2: saddle patch (a saddle patch in Risso’s dolphins is a darker area below the dorsal fin); 3: back-part; 4: head.

Figure 7. Example of beginning (a) and End stage (b) of Age class for “By Eye” method.

Raters had a detailed manual with descriptions and example pictures to help them assess the pictures. Overall there are 6 age classes (Calves, Juveniles, Sub-Adults, A1, A2 & A3) but the raters were asked to score each picture with a number between 1- 12. Since there scarification patterns overlap per class, due to aging within a class- the 6 proposed scarification classes were subdivided in a “start” (a) and an “end” (b) phase, generating a total of 12 subclasses (Figure 7).

Furthermore they were asked to do a second judgment if the animals were in the adult phase (A1-A3). This second test was a judgment between pictures of known females and known males and will be referred to as the gender test. This test was blind as raters were not aware of the purpose of this second test.

Figure 8. Age classes for Ruler.

Figure 9. Ruler placed on back of animal.

Figure 10. Variations of scar and mark types, 1: Example of an individual showing various scar and mark types; 2: Mark of a shark–bite; 3: Overlapping scar and mark types: several dots, probably suctions cups prey marks, shark bite and linear inner- species tooth marks; 4: Suction cup mark of a cephalopod prey; 5: Single linear inner- species tooth marks.

Ruler Classification

For the Ruler classification method we created a ruler where 30 small boxes were placed on the line from the blowhole towards the front of the dorsal fin. Different designs were tested prior with different block number, block sizes and ruler sizes. The design used here is a balance between necessary details within the blocks, block size and feasibility.

A manual with descriptions and example was given to each rater. We used 6 scarification types (Figure 8) to score the density of scars and marks on the skin visible in the boxes (Figure 9). The overall scores were averaged and resulted in 1 of the 6 scar types. We scaled our pictures towards the fixed scale of the ruler size (size of ruler: 1000pt x 68pt), using the software program GIMP. For some pictures we lost sharpness and therefore we could not zoom in more than 300% in order not to lose important details or sharpness.

You may encounter areas with few linear tooth- marks and odd looking marks (Figure 10). Figure 10 shows different scar and mark types which you will likely encounter during the scoring process.

RESULTS

As main statistic to judge agreement between raters the kappa statistics was used. An interpretation according to Landis and Koch (1977) can be found in Table 2.

Table 2. Interpretation of Kappa value. Κ Interpretation < 0 Poor agreement 0.01 – 0.20 Slight agreement 0.21 – 0.40 Fair agreement 0.41 – 0.60 Moderate agreement 0.61 – 0.80 Substantial agreement 0.81 – 1.00 Almost perfect agreement

By Eye The age classes were reduced to 1-6 instead of 1-12 as it was clear that the 12 classes were not well defined neither for rater group 1 (Biologists) nor for rater group 2 (General Public), respectively (Kappa=0.498, Kappa=0.437).

Rater Group 1: Biologists There were 15 raters which assessed the pictures from the test set “By Eye”. The Fleiss Kappa for multiple raters was used to judge inter rater agreement (Fleiss and Cohen 1973). The software program R was used with the library “irr”. The results show an overall substantial agreement between the raters (Kappa =0.734). The results for the different age classes can be seen in (Table 3). The lowest agreement seems to be for age class A2.

Rater Group 2: General Public The same method was applied for the general public group which had 13 raters in total. There was also substantial agreement between raters (Kappa=0.656) but not as

82 high as in the biologist rater group (Table 3). To identify a difference between the two rater groups a factorial ANOVA was carried out on the score data with the interaction of group and picture which resulted in no significant difference (p=0.884).

Table 3. Age class specific results for Inter Rater agreement of biologist raters and General Public (by eye method) Age Class Biologists General Public Κ p-value Κ p-value Calves 0.936 <0.001 0.848 <0.001 Juveniles 0.858 <0.001 0.702 <0.001 Sub -Adults 0.797 <0.001 0.701 <0.001 A1 0.692 <0.001 0.632 <0.001 A2 0.606 <0.001 0.551 <0.001 A3 0.710 <0.001 0.632 <0.001 ALL 0.734 0.656

Gender Test If the picture was scored as an adult age class A1-A3 the raters had to score it additionally choosing from examples of pictures. These examples showed an example of a female and a male in that age class. This was a blind trial so the raters did not know what that test was for. From the whole dataset only 59 and 62 pictures were classified by biologist and general public raters respectively in the adult classes and were used for the kappa test. There was moderate to fair agreement (Kappa=0.414, Kappa=0.337) for biologists and general public, respectively. As the prior score determined the choice available for the consecutive score the results were simplified to resemble female or male. The results are very discouraging with slight agreement (Kappa= 0.148) for biologists as well as general public (Kappa= 0.0708). This result indicates that gender cannot be determined using this methodology.

Rater vs. Expert Although we established substantial agreement between raters, a test against an expert opinion was necessary to not just establish agreement but also verify accuracy of this methodology. We only preceded with the biologists data as the agreement was higher within this group. The average of each picture was taken from all the 15 raters and rounded to the nearest age class. A simple 2 rater Cohen kappa was used to judge agreement which resulted in a moderate agreement (kappa= 0.554) (Table 4).

Table 4. Age class specific results for Inter Rater agreement of Biologists and Expert for the complete data set and without females Age Class All (n=120) Females excluded (n=90) Κ p-value Κ p-value Calves 0.943 <0.001 0.941 <0.001 Juveniles 0.948 <0.001 0.946 <0.001 Sub -Adults 0.452 <0.001 0.838 <0.001 A1 0.419 <0.001 0.842 <0.001 A2 0.441 <0.001 0.716 <0.001 A3 0.550 <0.001 0.762 <0.001 ALL 0.554 0.823

Although this is still moderate agreement we investigated which pictures were “miss- classified”. From 120 pictures, 76 were classified correctly and 44 differed from the expert opinion. From these 44, 30 pictures were from the class females (A1-A3). All female animals were classified in younger age class mostly by one sometimes by two age classes. Taking this bias into account and reducing the data set to 90 (excluding all female pictures) resulted in an almost perfect agreement (Kappa= 0.823).

Ruler

Rater Group 1: Biologists This group consisted of 14 raters. Due to 1 picture duplication the test set was reduced to 119. The Fleiss kappa test resulted in kappa=0.63 which is substantial agreement but is lower in contrast to the by eye method (Table 5).

Table 5. Age class specific results for Inter Rater agreement of biologist raters and General Public (Ruler Method) Age Class Biologists General Public Κ p-value Κ p-value Calves 0.841 <0.001 0.801 <0.001 Juveniles 0.595 <0.001 0.443 <0.001 Sub - 0.639 <0.001 0.436 <0.001 Adults A1 0.558 <0.001 0.453 <0.001 A2 0.573 <0.001 0.560 <0.001 A3 0.613 <0.001 0.625 <0.001 ALL 0.63 0.54

Rater Group 2: General Public There were 10 raters in this category. The inter rater agreement is not as high as in the biologist group and is in the moderate agreement category (Kappa= 0.54).The detailed results indicate a lack in agreement in all age classes except calves (Table 5).

Rater vs. Expert The same approach was followed as describe for the “By Eye” method. The agreement was considerable lower in contrast to the “By Eye” method (kappa=0.341). Adjusting it to exclude females improved the agreement (kappa= 0.531) but not to the extent as seen in the “By Eye” method.

DISCUSSION

Estimating age in cetaceans is a difficult task and current methodologies are limited to post-mortem techniques using teeth, ear plugs and/or eye lenses (exception body length) (e.g. Klevezal and Klejnenberg 1967; Lockyer 1972; George et al., 1999; Fearnbach et al., 2011). We propose to use the unique discoloration process in Risso´s dolphins which is caused by the accumulation of scars as an indicator to estimate age. This method is promising due to its non-invasive origin, its simplicity and practicality. By applying this method it is possible to expand the common 3 age class cetacean model (calf, sub-adult, adult) to a reliable 6 age class Risso’s dolphin model (calf, juvenile, sub-adult, adult1, adult2 adult3). Due to the long-term data set available, the

84 discolouration process was observed in detail and could be used to establish the proposed life history scar type determination model. This model was determined by using digital photographs from the back of Risso’s dolphins in conjunction with behavioural observations. Computer assisted methods to quantify the discolouration were trialled and deemed insufficient which is why this model was created using purely visual judgement and behavioural information. Au et al. (2011) used the dorsal fins of several carcasses which were photographed in a lab and converted into grayscale using Photoshop and Image J software. Here the % of scars could be measured precisely and was used to determine 3 classes of scarification. This approach only covers the adult age classes and does not cover the calf-subadult stages. We also tried computer assisted methods which worked fairly well in the older stages but not well in the younger age classes due to the colour conversion process. We believe that the our proposed method is the way forward as it covers the whole life span of the animals and not just part of it. Furthermore we believe that the dorsal fin area is not a good indicator as it stays relatively stable, and that the body accumulates scars more reliably.

This non-quantitative approach is favoured as it is easy to apply, reliable and time efficient. It was necessary to test that the proposed methods can be applied by anybody and is not rater biased. A similar approach is seen in other studies (especially cetacean acoustics) where raters were asked to judge whistle contours and classify groups (Janik 2000).

We proposed two different visual methods. The results clearly show that the “By Eye” method is favoured over the “Ruler” method. The advantages are clear: no prior image manipulation necessary, less time intensive, higher inter-rater agreement in both rater groups and almost perfect agreement with expert opinion. The results prove that anybody can almost perfectly classify Risso´s dolphins according to the proposed 6 class age model.

There was a slightly higher inter-rater agreement observed in the Biologist group in contrast to the general public although it was not significantly different. We believe this is a slight indication that with some training and feedback the obtained results could be improved.

Another interesting result is the observed bias in females. All females were classified younger indicating accumulating scars is gender related proving some sexual dimorphism in Risso’s dolphins. Risso’s dolphins’ diet consists mainly on cephalopods, deeming teeth unnecessary which is seen in the reduction of teeth retained (Clarke 1986). It is believed they are used as weapons and scars are an indicator for male quality and also used in fights for females (MacLeod 1998). Therefore males should be heavier scared then females which has been observed in this study. Females of a similar age are scared less and therefore classified older in contrast to males. Therefore additional information is necessary to apply this methodology accurately as the gender test also proved that it is not possible to identify the gender of an animal based on a picture. Furthermore we proved that the difference in scarring starts when reaching adulthood as earlier age classes (Calf, Juvenile, Sub- Adult) were correctly classified. Sub-Adulthood had a low agreement rate (kappa= 0.452) as A1 females were misclassified as sub-adults which was changed when females were taken out (kappa=0.838). The data set also included animals with

85 unidentified gender. Although they were classified correctly with the model without gender information in the adult age classes there is a 50% chance these are misclassified females. We believe that this method can be applied to other Risso’s dolphin populations around the world but caution is necessary when applying this method without extra information.

Preliminary results indicate this method can be used to distinguish between different age classes. Further work into gender differences, robustness and application of this method are going to be tested using long term followed individuals from Pico Island (Azores, Portugal).

It is of great ecological interest to gain insights in the longevity of these animals by using age-classes linked to age. For conservation issues its important have detailed insights in the age class composition of a marine mammal population, especially in area’s were certain animals are at risk due to various anthropogenic features.

ACKNOWLEDGEMENTS

Several pictures for this test were kindly provided by Lisa Steiner and João Quaresma. Useful comments on drafts and other reviews were given by Lotte Niemeijer, Lisa Steiner, Marc Fernandez & Peter Telleman. Melina Ruyter designed the Scarification Guides. And last but not least many thanks to all of our volunteers for taking the time to score our test set. This would have not been possible without you!!!

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9. A BRIEF REVIEW ON RISSO’S DOLPHINS OFF TAIWAN: ECOLOGICAL AND BIOLOGICAL CHARACTERS, AND POTENTIAL ANTHROPOGENIC THREATS.

Ing Chen 1,* and Lien-Siang Chou 2

1 School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK 2 Institute of Ecology and Evolutionary Biology, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 16017, Taiwan *Corresponding author; [email protected]

INTRODUCTION

Risso’s dolphins ( Grampus griseus ) are widely distributed in temperate to tropical oceanic regions, commonly sighted on both sides of North Pacific and Atlantic oceans, Mediterranean Sea and Indian Ocean (Baird 2009; Jefferson et al., 2013). The type specimen of Risso’s dolphin was salvaged from the northwest coast of France (Cuvier 1812), and further reference specimens were mainly collected from European waters (See review by True 1889; Kruse et al. , 1999). Current knowledge on the biology and ecology of Risso’s dolphins is mainly derived from studies conducted in European waters (see reviews by Bearzi et al., 2011; Evans, this issue). Several Risso’s dolphin populations in European waters have been identified and are being closely monitored (e.g. , Azzellino et al ., 2008; Hartman et al. , 2008; Boer et al. , 2013), as well as the populations identified around United States of America (see Marine Mammal Stock Assessment Reports prepared by National Marine Fisheries Service, NOAA, USA).

In contrast to those populations, Risso’s dolphins in Asian waters are relatively little studied. Of the few studies carried out on Rissos’s dolphins in this region, most of them were conducted off Japan, the northern limit of the species’ distribution in the Northwest Pacific (Miyashita 1993). Mizue and Yoshida (1962) reported a preliminary observation on the life history traits, feeding preferences, and taxonomy of Risso’s dolphins, based on the examination of three dolphin schools captured in the western Kyushu waters during 1959–1961. The study suggested that Risso’s dolphins, in that region, perform a parturient migration in summer and a feeding migration during winter. A parturient migration group usually consists of 20–30 dolphins, and a feeding migration group consists of approximately 200 individuals. The study also stated that Risso’s dolphins prey exclusively on squids, with the identification of some big-fin reef squids ( Sepioteuthis lessoniana ) in the stomach contents from the dolphins captured in January. In addition, this study found no significant morphological differences ( i.e. , the size of skull and number of teeth) between the dolphins from the west Kyushu (Southwest Japan) and the Northeast Japanese waters.

Amano and Miyazaki (2004) reported a more sophisticated analysis on group composition and quantified life history parameters for Risso’s dolphins in Japanese waters, based on a group of 79 dolphins captured off Taiji in November 1990. This study suggested that Risso’s dolphins reach sexual maturity between 10–12 years of age in males and 8–10 years in females. The standard adult-body-length is 270 cm and no significant sexual dimorphism was observed between male and female body

89 lengths. The analysis on the age of calves and fetuses agreed with the earlier study (Mizue and Yoshida 1962) that the major calving season for Risso’s dolphins is from summer to autumn. The majority of individuals in a group are females at different reproduction stages, and only a few males stay with the group after reaching their sexual maturity.

By analyzing sightings data from 34 ship-board surveys conducted in 1983–1991, Miyashita (1993) suggested that there are three major aggregations of Risso’s dolphins during the summer: in the Japanese coastal waters, between longitudes 148°– 157°E and east of 162°E. An estimation for the overall abundance of Risso’s dolphins in the Japanese Northwest Pacific at the time was 83,289 dolphins. Kasuya (2007) reported that there were 171–1,298 Risso’s dolphins being hunted in Japanese coastal waters between 1995 and 2004.

On the other hand, Risso’s dolphins are not only distributed around Japanese waters, but also further south in more tropical regions, including Taiwan, the Philippines and Indonesia (Talyor et al., 2012). Studies on Risso’s dolphins in these regions are sparse, although one might assume that findings from Japanese specimens would similarly apply, at least for individuals off Taiwan, as we assume individuals can move freely between these areas (see below). In this paper, we reviewed the current knowledge of Risso’s dolphins in Taiwanese waters, and intended to shed some light on the biological/ecological status of Risso’s dolphins in the tropical region of the Northwest Pacific Ocean. Note that many documents cited herein are government reports and student theses and the data presented in those documents may not have passed through a scientific peer-review process, therefore we would suggest that further interpretations be made with caution.

RISSO’S DOLPHINS IN TAIWANESE WATERS

Distribution and Abundance

Risso’s dolphins are one of the most commonly encountered cetacean species in Taiwanese waters. Although stranded dolphins can be found along the beaches island- wide (see below), the sightings of Risso’s dolphin groups are predominantly reported from the east coast (Fig. 1). Chen (2001) studied the cetacean fauna composition, distribution and abundance in the northeast coast (off Ilan, 25°00’–24°10’N, 121°50’– 122°10’E; Fig. 1) by analyzing observational data taken during boat-based line- transect surveys over 97 days, between March 1998 and November 1999, showed that Risso’s dolphin was one of the four most commonly sighted species in this region, and they were mostly encountered at the southern part of survey area, over the steepest slopes and deepest waters. The study also showed that Risso’s dolphins in Ilan waters were more often seen during the summer months than in other seasons. The abundance of Risso’s dolphins in the surveyed region was estimated to be 218 (CV=29.39%).

A 67-day field survey conducted along the central east coast of Taiwan (between Hualien and Shiti Ports, Fig. 1) in the summer of 1996 and 1997 found that Risso’s dolphins were the most frequently sighted cetacean species in this region (29.9% of total 131 cetacean sighting events) (Yang et al. , 1999). The prevalence of Risso’s dolphins in the east coast of Taiwan was in accordance with another field study

90 conducted along the southeast coast, off Chengkong (Fig. 1) (Yeh 2001). This study also showed that Risso’s dolphins were the most common cetacean species in the surveyed area (29.7% of total sighting records), and they were also more abundant in summer (although it should be noted that no survey work was conducted during the winter due to severe weather conditions). Wang (2000) also reported a high sighting rate of Risso’s dolphins (36.4% of total sighting records) along the southern coast (Kenting waters), with a rough estimation for the abundance of Risso’s dolphins (n=226) in the study region.

Figure 1. Sighting locations (solid circles) of Risso’s dolphins around the coast of Taiwan (1998–2007). Survey area is marked in yellow. Ilan, Hualien, Shiti and Chengkong are the four major ports for whale-watching tourism in Taiwan. (Modified from the Fig. 4a,c in Chou 2007).

In contrast, a preliminary transect survey conducted in the southwest coast of Taiwan reported only four encounters of Risso’s dolphins out of 24 cetacean sightings (Huang, 1996). The result was based on 12 survey trips at seven transect lines in the area between south of Penghu Archipelago and east of Kenting (25°00’–24°10’N, 121°50’–122°10’E) in December 1994–January 1996, and estimated the abundance of Risso’s dolphins in the study region as 153. To our knowledge there is no scientific report indicating Risso’s dolphins inhabit in the northwest coast of Taiwan. This could be due to the lack of survey effort for the offshore waters along the north and west coast (Chou 2007; Fig. 1), although it is also remarkable that the bathymetric topography of the Taiwan Strait, waters adjacent to the west coast of Taiwan, appears to be too shallow to be considered as a typical habitat for Risso’s dolphins (i.e ., water depth c. 60m [Jan et al ., 2002] vs. 400–1000m [Baird 2009]).

Figure 2. Fifty-eight stranding sites (solid circles) of Risso’s dolphins around the coast of Taiwan (1994–2012). (Chou, unpublished data)

Risso’s dolphins are also one of the most commonly stranded cetacean species in Taiwan (Huang 2005; Chou unpublished data). Sixty-three Risso’s dolphins were found stranded along the coasts of Taiwan (including Penghu Archipelago, Green Island and Orchid Island) in 1994–2013 (Fig. 2; Chou unpublished data). Those found

92 stranded along the coast across ‘unusual’ habitats ( i.e. , the shallow west coast) may have resulted from drifts or currents (see similar examples in Bilgmann et al., 2011). Because there seems to be no significant seasonality in those Risso’s dolphin strandings, it is inferred that Risso’s dolphins may occur in Taiwanese waters year- round (Chen et al., 2011a). The re-sighting record of a rehabilitated dolphin has possibly demonstrated that Risso’s dolphins exhibit a wide home range in Taiwanese waters (Yang et al., 2001). This case study reported an adult male dolphin stranded on the coast of Miaoli county (northwest Taiwan) in July 2000, was rescued and rehabilitated from Taipei (north Taiwan) in September of the same year, and the dolphin was re-sighted off the Ryukyu Islands, about 770km north of the release site two weeks later. There is no information available on the home range and site fidelity of Risso’s dolphins in this region, though a preliminary genetic investigation has revealed that dolphins from Taiwanese and Japanese waters share several common mitochondrial DNA haplotypes, which suggests a genetic connection between Taiwanese and Japanese dolphins (Chen et al., 2011b, see below).

Given the difficulty in determining animal range and distribution and combining patchy sightings data from different surveys in different locations, the overall abundance of Risso’s dolphins in Taiwanese waters has not been estimated (reviewed in Chou 2007). Nevertheless, records from field surveys, stranding, and bycatch (see below) all indicate that Risso’s dolphins could be abundant in Taiwanese waters.

Diet and Life History Traits

For insights into the diet of Risso’s dolphins in Taiwanese waters, the stomach contents were examined from 27 stranded or bycaught individuals salvaged between 1994 and 2001 (Wang 2003; Wang et al., 2012). This study found that Risso’s dolphins in Taiwanese waters fed exclusively on cephalopods, providing Risso’s dolphins with the narrowest feeding niche among the three most common cetacean species along the east coast of Taiwan (Wang et al., 2012). This study identified 15 species of mesopelagic squids from 13 cephalopod families in the stomach contents, and the enoploteuthid squid, Enoploteuthis chunii (family Enoploteuthidae), formed the majority of prey in the Risso’s dolphin diet off Taiwanese waters (90.5% in number, 88.9% in occurrence). There seems to be a seasonal shift in species preyed upon by Risso’s dolphins, although the enoploteuthid squid is always the major prey species throughout the year. In addition, it was reported that most of the enoploteuthid squids consumed by Risso’s dolphins were likely to be adult squids, which were generally found at water depths around 300–600m during the daytime and 150m at night (Wang 2003).

The life history traits of Risso’s dolphins in Taiwanese waters were identical to those reported from Japanese specimens. Chen et al. (2011a) measured the body length of 92 Risso’s dolphins stranded or bycaught in 1994–2008, they also recorded the reproductive maturity of 33 individuals and Growth Layer Groups (GLGs) in the tooth sections to determine the age for 28 individuals. The results showed no significant sexual dimorphism in adult body length, and that adult body lengths rarely exceed 3m. This study also suggested that dolphins reach sexual maturity at lengths around 2.4–2.5m in females and 2.5–2.6m in males at an age of approximately 10 years. However, it should be noted that these statistics were ambiguous because the sample size for determining age and size at sexual maturity was small. On the whole,

93 these findings agreed with a previous study on a group of Risso’s dolphins captured in Japanese waters (Amano and Miyazaki 2004), and showed the body size of the dolphins in the Northwest Pacific region to be smaller than other oceanographic regions.

Group Size, Behaviours and Social Structure

Risso’s dolphins around Taiwan usually aggregate into groups containing less than 40 individuals (Chen 2001; Yeh 2001; Lin 2003). The mean group size in the northeast was estimated as 10.97 (Chen 2001), 32.5 along the central-east (Lin 2003), and 17 along the southeast coasts (Yeh 2001). Group size likely varied with group composition (see below). Feeding and nursing of offspring were commonly observed in spring–autumn (Chen 2001; Yeh 2001; Kuo 2002; Lin 2003). Inter-species association was a common phenomenon for Risso’s dolphins in Taiwanese waters, and mixed species assemblages with Fraser’s dolphin ( Lagenodelphis hosei ) appeared to be the most common (Yeh 2001; Kuo 2002; Lin 2003).

A preliminary photo-ID survey conducted along the east coast of Taiwan during the spring-autumn seasons in 2000–2001 provided some insights into the behaviour ecology of Risso’s dolphins in Taiwanese waters (Lin 2003). In that study, Risso’s dolphin groups were divided into four classes based on the presence/absence of mother-calf pairs, and body colour-patterning of group members. The four classes were: 1) Calving Group, a group containing at least on mother-calf pair; 2) Whitish- adult Group, a group containing only ‘whitish’ adults (individual body size over 2.8m, white scarring covered more than half of the body), 3) Grayish-adult Group, a group contained only ‘grayish’ adults (individual body size over 2.8m, scarring covered less than half of the body) and 4) Mixing Group, a group containing both ‘whitish’ and ‘grayish’ adults. Group sizes were significantly different between these four groups. The calving group usually aggregated into a larger group size (ranging from 7 to 200 dolphins; average group size of 64.3). Similar results have been reported in off the southeast coast (Yeh 2001). ‘Mixing’ and ‘Calving’ groups were the most commonly observed, constituting 43% and 41% respectively of the total 186 observations. Interestingly, the ‘courting behaviour’, which was defined as ‘tight, physical contacts, including both rubbing and chasing amongst individuals’, was usually observed in ‘Mixing’ groups, involving one ‘whitish’ and two to four ‘grayish’ adults. Lin (2003) suggests that Risso’s dolphins in Taiwanese waters may live in sex-separated groups by assuming those ‘whitish’ dolphins were males and ‘grayish’ dolphins were females. Furthermore, the study also suggests that the ‘Mixing’ groups and the courting behaviour were likely identical to the ‘mix-sex’ group and ‘herding’ behaviour observed in bottlenose dolphins ( Tursiops truncatus ) in Shark Bay, Australia. Moreover, the analysis showed that the ‘whitish’ and ‘grayish’ groups occupied different regions with different water depths, thus indicating a habitat partitioning may exist between males and females.

An analysis on the social structure of Risso’s dolphins was also presented in Lin’s 2003 study. Within the two-year survey period, 670 dolphins were identified based on 1196 high quality photos, and 94 of them were re-sighted in the second year of the study (29 ‘grayish’ and 65 ‘whitish’ adults). A tight social association was found amongst ‘whitish’ adults (presumably males), whereas the association index was generally low between ‘grayish’ adults (presumably females). Because this

94 asymmetry in association patterns coincided with the behaviour observed in the bottlenose dolphins in Shark Bay (see above), this implies that Risso’s dolphins in Taiwanese waters might employ a similar social system to bottlenose dolphins. However, this study was based on a new photo-ID catalogue that was established over a relatively short timeframe (two years), therefore the low re-sighting rate could have indicated that this study only sampled a small proportion of the entire Risso’s dolphin population in the region. We would suggest a cautious re-examination of the social structure for Risso’s dolphins in Taiwanese waters by including further data, taken over a longer observation period and over a larger geographic area. Genetic approaches to determine the sex of individuals and kinship between individuals within and between groups would also be valuable.

Population Genetics

The first study on the population genetics of Risso’s dolphins in Taiwanese waters was conducted through an examination of the sequence variation in mitochondrial DNA (mtDNA) of 92 dolphins from waters off Taiwan and Japan (Chen et al., 2011b). A 588 base pairs of mtDNA control region sequence was examined for 43 Taiwanese and 49 Japanese samples, the study identified 44 variable sites defining 34 unique haplotypes for Risso’s dolphin in this region, and found that both genetic diversity ( h) and nucleotide diversity ( π) were high in both countries (Japan: h=0.941, π=0.013; Taiwan: h=0.899, π=0.012). Only a marginal difference in haplotypic frequency was detected between Taiwan and Japan ( FST =0.021, P=0.04), suggesting an identical genetic structure of Risso’s dolphins in Taiwanese and Japanese waters, although some level of population differentiation might be occurring. In addition, this study found significant population differentiation between Risso’s dolphins in the Northwest Pacific (Taiwanese and Japanese waters) and the European waters (the Mediterranean Sea and UK waters; Gaspari et al., 2008) ( FST =0.25, P<0.01; ɸST =9.26, P<0.01) with no haplotype shared between them. However, the differentiation does not result in a reciprocal monophyly in the genealogy, suggesting a complicated history for current population structure of Risso’s dolphin in the world.

Interactions with Human and Conservation

Risso’s dolphins, along with most other cetacean species off Taiwan, are listed as a ‘Rare and Valuable Species (Class II)’ and protected by the Wildlife Conservation Act in Taiwan since 1990 (Forestry Bureau 2006). So far, the harassment from whale- watching tourism and incidental catches in the coastal fisheries is, if any, the main anthropogenic threat to Risso’s dolphins in Taiwanese waters (Chou 2004; Perrin et al., 2005). Two studies based on summertime observations from different whale watching courses off the east coast of Taiwan demonstrated a subtle-to-significant short-term negative impact of whale watching tourism to Risso’s dolphins. The one conducted off Shiti port found Risso’s dolphins change their behaviour status in response to disturbance from whale watching boats (Yu 1999). In another study, based at Chengkong port, Risso’s dolphins were seen to perform more ‘negative reactions’ when any whale watching boat were present (Kuo 2002). The long-term impact of the harassment from the whale watching tourism remains uncertain due to the lack of a consistent monitoring system on cetacean resources in this region.

Risso’s dolphins are commonly bycaught in Taiwanese coastal fisheries; usually in the drift-net fishery (Chou 2001; Chou 2006). Based on data derived from interviews and surveys over a three-year survey on cetacean bycatch in Taiwanese waters, it was suggested that the bycatch rate of small cetaceans in Taiwanese waters was 0.32–0.40 per fishing boat per day during the main fishing season (September–February) in 2004–2006; estimated 2,770 small cetaceans being bycaught off the east coast of Taiwan in 2006 (Chou 2006). Although there is no precise estimate available regarding the annual number of bycaught Risso’s dolphins, this study proposed an empirical bycatch proportion of 45.9% Risso’s dolphins (based on data from two major fishing sites off the east coast, Shiti and Chengkong, during the fishing season in 2006) and therefore suggesting approximately 1,274 Risso’s dolphins were bycaught off the east coast in 2006. A survey conducted in 1993–1995 for studying cetacean carcasses landed in four major fishing ports in the east coast of Taiwan (Nangfang Ao, Hualien, Shiti and Chengkong) suggested a higher estimation for the bycatch rate in Taiwan (n=25,680–38,520 each year; Perrin et al. , 2005), however the estimate for Risso’s dolphins was not specified in the report. Note that the estimates proposed in both studies ( i.e., Perrin et al. , 2005 and Chou 2006) were based on small sample sizes—for instance there were only 37 bycaught dolphins retrieved in Chou’s three-year survey period—therefore the estimates may be subject to limited statistical power. Further survey effort and cautious re-examination is needed to validate this estimate. The bycatch impact on Risso’s dolphin populations also deserves further investigation.

SUMMARY

Current information suggests that Risso’s dolphins are a common cetacean species off the east coast of Taiwan, usually found in regions where water depth is between 500– 1500m. Many biological and ecological characters observed in the dolphins from Taiwanese waters are similar to those from other oceanographic regions, such as group size (Mizue and Yoshida 1962; Kruse 1989), preference to shelf-edge, deep- water habitat (Kruse 1989; Baumgartner 1997; Azzellino et al. , 2008), preying exclusively on squids (Mizue and Yoshida 1962; Würtz et al. , 1992), and age of sexual maturity (Amano and Miyazaki 2004). Preliminary satellite tracking and genetic data support the notion that Risso’s dolphins off Taiwan and Japan are likely from the same population. Risso’s dolphins in Taiwanese waters are potentially vulnerable to human activities, such as disturbance from the whale-watching tourism and fisheries bycatch. It should be noted that most of current knowledge has been derived from limited observation or small sample sizes; therefore further study is needed. The answers to key biological and ecological questions important to conservation initiatives such as population size, social structure and group composition are still unclear. Further studies are needed to evaluate the extent of anthropogenic impacts on the Risso’s dolphins in the waters off Taiwan.

ACKNOWLEDGEMENTS

We thank Howard Grey and Shane Guan for their comments, which had improved the manuscript significantly. Lien-Siang Chou would like to thank Hsin-Yi Yu for her assistance in collecting field data. This review paper received no specific grant from any funding agency, commercial or not-for-profit sectors, however Lien-Siang Chou would like to acknowledge the grant support form the Council of Agriculture,

Government of Taiwan (grant numbers 90 AS -1.4.5-FA -F1(27), 90 AS -1.4.5-FA -F1(28), 91 AS -2.5.1-FA -F1(25), 92 AS -9.1.1-FA -F1(26), 93 AS -9.1.1-FA -F1(13), 94 AS -14.1.1-FA - F1(12), 95 AS -14.1.1-FA -F2(3), 96 AS -15.1.1-FA -F3(2) and 97AS-15.1.1-FA-F3(2)); National Science Council (grant numbers NSC89-2311-B002-090, NSC94-2621- Z002-030 and NSC95-2621-Z002-021); Government of Ilan County, Taiwan; Government of Taitung County, Taiwan and Yamaha Motor Taiwan for supporting Risso’s dolphin researches in Taiwan since 1994.

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10. INFORMATION ABOUT RISSO’S DOLPHINS FROM THE UK CETACEAN STRANDING INVESTIGATION PROGRAMME (CSIP)

Jepson, P.D. * and Deaville, R.

Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK. *Corresponding author; email: [email protected]

Between 1990 and 2011, 171 Risso’s dolphins ( Grampus griseus ) were reported stranded around the UK coast to the Defra funded UK Cetacean Strandings Investigation Programme. Of these, the majority were found stranded in Scotland (n=128) with smaller numbers in Wales ( n=21), England ( n=20) and Northern Ireland (n=2). Over this period, no discernible trend was noted in inter-annual strandings. Thirty six Risso’s dolphins were retrieved for systematic post-mortem examination during this period, with a range of causes of death being established (Table 1).

Table 1. Causes of death in Risso’s dolphins examined at post-mortem in the UK (1990-2011) Cause of Death Number Bycatch/entanglement 7 Live stranding 5 Starvation 5 Gas embolism 4 Dystocia/stillborn 4 Infectious disease 4 Physical trauma (unknown origin) 1 Not established 6 Total 36

A relative preponderance of gas embolism cases was noted in this species (11% of examined animals), in contrast to other more shallow diving cetacean species examined by the CSIP during the same period (Jepson et al ., 2003, Jepson et al ., 2005, Deaville and Jepson 2011). Recently published work has identified the presence of elevated levels of nitrogen within gas cavities found in organs of cetaceans affected by gas embolism (Bernaldo de Quirós et al. , 2011), thus confirming that this is a condition in cetaceans which is analagous with decompression sickness in humans.

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IMAGES

Plate 1- Risso’s dolphin stranded at Anglesey, Wales (reference number SW2009/301, image credit Marine Environmental Monitoring)

Plate 2- Abnormal spleen of the Risso’s dolphin stranded at Anglesey in Wales, showing large number of gas filled cavities (image credit Marine Environmental Monitoring).

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Plate 3 and 4- Gas extraction from the spleen of SW2009/301.

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Deaville, R. and Jepson P.D. (compilers). 2011. UK Cetacean Strandings Investigation Programme Final report for the period 1 st January 2005-31 st December 2010. Avaliable at: http://randd.defra.gov.uk/Document.aspx?Document=FinalCSIPReport2005- 2010_finalversion061211released[1].pdf.

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11. CALL FOR ACTION FOR RISSO’S DOLPHIN IN THE NORTH EAST ATLANTIC REGION

Mark Simmonds 1,2, Marijke de Boer 3,4,2 , Sonja Eisfeld 2, Sarah J. Dolman 2, Nicola K. Hodgins 2, Peter G. H. Evans 5,6 , Ing Chen 7, Karin L. Hartman 8,9 , Steve Geelhoed 3, Gemma Paterson 10 and Olivia Harries 10

1 Humane Society International, c/o 5 Underwood Street, London N1 7LY, UK. 2 Whale and Dolphin Conservation (WDC), Brookfield House, 38 St Paul Street, Chippenham, Wiltshire, SN15 1LJ, UK (Previous affiliation for MS) 3 Wageningen IMARES, Institute for Marine Resources and Ecosystem Studies, Postbus 167, 1790 AD Den Burg, The Netherlands 4 Wageningen University, Department of Aquatic Ecology & Waterquality, Wageningen, The Netherlands 5 Sea Watch Foundation, Ewyn y Don, Bull Bay, Amlwch, Isle of Anglesey LL68 9SD, UK 6 School of Ocean Sciences, University of Bangor, Menai Bridge, Isle of Anglesey LL59 5AB, UK

7 School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK 8 Department of Biology, University of the Azores, Rua Mãe de Deus 13, 9501-801, Ponta Delgada, Azores, Portugal 9 Nova Atlantis Foundation, Risso's Dolphin Research Center, Rua Dr. Freitas Pimentel 11, 9930-309, Santa Cruz das Ribeiras, Lajes do Pico, Azores, Portugal 10 Hebridean Whale and Dolphin Trust, 28 Main St, Tobermory, Isle Of Mull PA75 6NQ UK

Participants in the 2012 European Cetacean Society (ECS) workshop on Risso’s dolphins, Grampus griseus , proposed the following statement for consideration and potentially adoption by the Annual General Meeting (AGM) of the ECS:

‘Further to its 2012 Workshop on Risso’s dolphins, Grampus griseus , which recognised distinct populations, critical habitat areas and a range of threats, the ECS calls for the establishment of protected areas for this species [including via its addition to annex II of the Habitats Directive].’

The participants also suggested that the ECS might call on the IUCN to urgently re- review the status of this species. The statement was deferred for further consideration by the 2012 meeting but then adopted at next ECS AGM in April 2013 in the slightly modified form presented in Chapter 2.

Here we provide some further background to the statement.

There remains little published information about the Risso’s dolphin when compared to many other dolphin species; although, as the workshop showed, there have been some significant advances in understanding its biology and the problems that it faces. The dearth of published information may be caused in part by the low densities and patchy distribution that this species exhibits across its European range (Reid et al ., 2003; Evans, 2008; Bearzi et al ., 2011), and the fact that its preferred habitat is often difficult to access as it includes the deep waters off the continental slope and outer shelf (typically at depths of 400-2,000 m), especially where there is steep bottom topography. The species is also found in deeper waters and some oceanic regions

104 beyond the continental shelf. Significantly, there are no global population estimates or trends.

The IUCN previously categorised the species as being data deficient. However, when it published its latest review, in 2012 (Taylor et al ., 2012), it re-classified the species as ‘Least Concern’ . The IUCN also recognises a genetic distinction between the population in the Mediterranean and that in the eastern Atlantic (see Gaspari et al , 2007). In its global review, the IUCN took note of some ongoing directed takes and highlighted bycatch and loud noise as other threats.

The separate IUCN assessment for the Mediterranean population (Gaspari & Natoli, 2012) found this population to also be ‘Least Concern’, and highlighted the threats posed by fisheries, noise and also chemical contaminants. Risso’s dolphins in the Mediterranean were reported as ‘frequently found entangled in fishing nets’, with bycatch in longlines and gillnets reported in Spain and Italy, and they are the most common species caught by the longline fisheries in the western Spanish Mediterranean (Macías López et al ., 2012). It was further noted by Gaspari & Natoli (2012) that the Mediterranean animals carried ‘substantial contaminant burdens’.

Whilst traditionally treated as a panmictic species, similar genetic distinctions to that recognised between the Mediterranean and eastern Atlantic populations may exist elsewhere. Chen et al., (2011) for example recognised a morphologically distinct population in the northwest Pacific. Genetic sampling also indicated that the Risso’s dolphins in the UK had lower genetic diversity than those sampled in the Mediterranean (Gaspari et al., 2007). Gaspari et al. , (2007) also noted that "results indicate that the UK Risso’s dolphin population should be identified as a separate management unit when considering conservation strategies in light of potential anthropogenic impact". In the UK and Ireland, Risso’s dolphins frequently occupy shallower coastal habitats, over slopes of 50-100 m depth (Evans et al. , 2003; Evans, 2008; Wall et al ., this volume). This raises the possibility of the existence of different ecotypes and also underlines the ongoing lack of knowledge about this species across Europe.

Arguably, as a reflection of the apparent rarity of this species and/or the lack of information about it, it has been given various legal designations intended to improve its status: • Listed on Appendix II of the Bern Convention; • Listed on Appendix II of the Bonn Convention; • Listed on Annex IV of the EU Habitats & Species Directive (with all other European cetaceans); • On Annex A of EU Council Regulation 338/97 on the protection of species of wild fauna and flora therefore treated by the EU as if they are included in CITES Appendix I and fully protected from international trade; • ‘Priority Marine Feature’ and a ‘Search Feature’ under the Scottish marine protected area (MPA) project, resulting from the Marine (Scotland) Act 2010; • ‘Species of principal importance’ in Wales (UK; S.42under section 42 of the Natural Environment and Rural Communities Act (NERC) 2006; and Risso’s dolphins are also on the original UK Biodiversity Action Plan priority species list of 2007;

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There have been few studies on the social structure of this species (Gaspari, 2004; Bearzi et al ., 2010). Recent field work in the Azores, off Pico Island, has shown that, individuals have long-term bonds and they occurred in pairs or stable clusters of 3–12 individuals, with strong associations between adult males and between adult females (Hartman et al ., 2008). This ‘stratified social organisation’ is different to that seen in other cetacean species and may have important conservation implications.

In addition, Evans (2008), Hartman et al . (2008), Dolman and Hodgins (this volume), and de Boer et al. (this volume) report evidence of strong site fidelity for Risso’s dolphins in various parts of its range, including nursery areas. In a recent study, spatial and temporal preferences of nursing Risso’s dolphins off Pico Island , show a pattern of segregation. The pods with younger calves were larger and showed a significantly distinct distribution, being present closer to shore, whereas the other groups used a wider offshore area. The peak of the calving season took place between June and September. These results strongly suggest the existence of critical habitat areas for this species (Hartman et al . in review). Other critical habitat areas that could be potentially identified include the waters of North Wales, the Western Isles of Scotland, and parts of the Mediterranean.

The intensity of whale watching activities and in particular swim-with tours around the Azores was identified during the workshop as being of concern (Hartman et al ., 2006), and especially the swim-with operations in areas where mothers and calves are regularly found (K. Hartman, pers. comm .). In a recent study based on 172 observations, Visser et al . (2011) found that Risso’s dolphins observed off Pico Island, during 2004 altered their daily resting patterns in the presence of whale watching vessels.

Harassment of Risso’s dolphins has also been reported off the Italian island of Ischia where another resident Risso’s dolphin population is reported (Miragliuolo, 2004). Increases in numbers of recreational craft also increase the risk of collisions with vessels or propellers.

In addition, Dolman and Hodgins (this volume) noted that as Risso’s dolphins are approaching the northern limit of their range in UK waters, climate change may have an effect on their distribution and they also highlighted the threats from increasing aquaculture and offshore developments including marine renewable energy developments (see also Simmonds & Brown, 2010). Clearly, the Risso’s dolphin’s prey preference for deep sea schooling cephalopods can be expected to have a strong influence on its distribution and there is some historical evidence for this in the Pacific (Taylor et al. , 2012).

The IUCN review also highlighted the threat from noise to this deep diving species, making special mention of the likely vulnerability of Risso’s dolphins to naval sonars and seismic surveys. The significance of this threat is further underpinned by studies on stranded individuals in the UK between 1990 and 2010. Of 36 necropsies conducted, four exhibited ‘gas embolisms’ (Deaville & Jepson, this volume), which may be symptomatic of exposure to very loud noise (Jepson et al. , 2005). In addition, bycatch/entanglement was identified in 7 individuals, 5 had live stranded, 5 had starved, 4 were cases of dystocia/stillbirth, and 3 were infected with meningoencephalitis .

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CONCLUSIONS

Previously, the vulnerability of this dolphin to human activities has been believed to be similar to that experienced by other dolphins (Wharam & Simmonds, 2008). This was never a safe assumption. The picture which is now emerging about the particular social structure of Risso’s dolphins, their discontinuous distribution and regular use of certain habitats, the harassment affecting them in some places, the relatively small size of many local populations, and recent evidence supporting their potential high vulnerability to loud noise - all still compounded by an overarching lack of data – means that precautionary actions to conserve them need to be stepped up. This should include protecting them from bycatch and loud noise, and, as the 2012 ECS workshop indicated in the statement that it recommended to the ECS, it should include the development of appropriate marine protected areas in those localities where the species has been found to regularly occur in numbers.

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