Basking Shark Forum 2024 - Programme & Abstracts

Basking Shark Forum 2024

©Andrew Pearson

Programme and Abstracts

1st February 2024

*All times in GMT

9:15 – 9:30 am

Opening address and housekeeping

Shark Trust team

Welcome and housekeeping

Rupert Ormond

Opening address

9:30 – 10:50 am

Session 1 - Overviews/Long term studies

Chair: Lucy Hawkes

Session introduction

David Sims

Foraging, social behaviours and population structure: Recent basking shark research at the Marine Biological Association

Eric Stephan

APECS’ ongoing research on basking shark in French waters

Sadie Gorvett

30 Years of Data Collection

Shane Wasik

Collaborative citizen science & basking shark tourism around West Scotland

Rupert Ormond

Basking Sharks: small mysteries in big sharks Q&A

10:50 - 11:05 am

Break

11:05 – 12:15 pm

Session 2 - Behaviour & Biology

Chair: Matt Witt

Session introduction

Simon Berrow

Evidence of courtship behaviour by basking sharks in Irish waters

Jess Rudd

Spying on the secret lives of basking sharks

Chelsea Gray

An Individual-Based Model of Basking Sharks in Ireland

Haley Dolton

Body temperature dynamics of basking sharks Q&A

12:15 - 1:00 pm

Break

2

1:00 – 2:15 pm Chair: David Sims

Session 3 - Spatial Ecology & Policy Session introduction

Peter Miller Claudia Junge & Antonia Klöcker Jonathan Houghton

Ocean fronts and stratification influence the distribution of basking sharks and marine biodiversity On the edge – deciphering distribution and movement patterns of basking sharks in the arctic Basking Sharks: Lessons from the EU SeaMonitor Programme (2019-2023)

Rona Sinclair

Future Directions – NatureScot perspective Q&A

2:15 - 2:30 pm 2:30 – 3:45 pm Chair: Simon Berrow

Break Session 4 - Data & Collaboration Session introduction

Harriet Allen

Historic data management: challenges and future directions

Matthew Witt

A new acoustic telemetry network for basking sharks in NW Scotland

Kristina Øie Kvile

Present and future basking shark hotspots along the Norwegian coast

James Thorburn

Assessing the potential of acoustic telemetry to underpin the regional management of basking sharks (Cetorhinus maximus)

Alexandra McInturf

Return of the shark: Conservation insights from 50 years of basking shark (Cetorhinus maximus) sightings in Irish waters Q&A

3:45 - 3:55 3.55 – 4:40 pm Moderator: Claudia Junge

Break Session 5 - Next Steps Discussion session: Future workshop, key themes, Meeting close

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Session 1 - Overviews/Long term studies David Sims Foraging, social behaviours and population structure: Recent basking dws@MBA.ac.uk shark research at the Marine Biological Association Authors: Institutions:

David W. Sims1,2, Emily J. Southall1, Lilian Lieber1 1. Marine Biological Association, The Laboratory, Citadel Hill, Plymouth PL1 2PB 2. University of Southampton, School of Ocean and Earth Science, National Oceanography Centre Southampton (NOCS), Southampton SO14 3ZH

The Marine Biological Association (MBA) in Plymouth, UK, has undertaken scientific research on the biology and ecology of the basking shark since the 1960s. Research has revealed, for example, the buoyancy of basking sharks, measured feeding and cruising swimming speeds to estimate energy intake and expenditure, quantified use of thermal fronts for selective foraging on specific zooplankton assemblages, annual social behaviours along fronts, and the first long-term, trans-seasonal satellite trackings showing productivity ‘wave’ following, diel and tidal vertical movements and no evidence for winter ‘hibernation’.

These tracking data were used in conservation proposals in 2002 and 2005 resulting in successful listing of basking sharks on Appendix II of CITES (2003) and CMS (2006). Since the 2009 Isle of Man conference on “Basking Sharks: A Global Perspective”, MBA research has explored foraging movements and social behaviour using direct observations and electronic tagging, and migratory and population structuring using genetic tagging. Results have identified that surface frontal activity is a predictor of basking shark presence in the north-east Atlantic, both over seasonal timescales and in near real-time, and from work with colleagues in Aberdeen has shown there is high incidence of basking sharks returning to specific locations within and between years, with significant temporal (early season sharks) population structuring within the northeast Atlantic despite generally high genetic connectivity among aggregation sites. More recently with collaborators in Ireland, circling behaviours of non-feeding males and females in a ‘torus’ were investigated and found to be consistent with annual courtship reproductive behaviour, further highlighting northeast Atlantic coastal waters as a critical habitat for basking sharks.

Eric Stephan asso@asso-apecs.org

APECS’ ongoing research on basking shark in French waters

Authors: Institution:

Eric Stephan, Alexandra Rohr, Félix Gendrot Association Pour l’Etude et la Conservation des Sélaciens (APECS), Brest, FRANCE

APECS is currently engaged in two projects on basking shark in French waters: a public sightings recording scheme and a satellite tagging project.

The national public sightings recording scheme started in 1998. While sightings are reported from most of the French waters, the results over a 25 years period show that only south and west coasts of Brittany can be considered as a regular sighting area were one hotspot has been identified. The results also show changes during the recent years in some areas, either in terms of sightings number or sightings period or the both.

In parallel, APECS deploys satellite tags on basking sharks in Brittany since 2009. During spring, 10 sharks were tagged with one tag (5 with a PSAT tag and 5 with a SPOT tag) and one shark was double tagged.

Usable data were obtained for 6 sharks with deployment periods lasting between 37 and 834 days.

Connections between Brittany and other known sightings hotspots in Europe (Scotland, Ile of Man, west and south Ireland) were highlighted. Southward movements were also recorded for two females around 6.5 meters long. The first one has been located west of the coast of Mauritania in February 2017. The second went even further south, at least as far as off Cape Verde during the winter of 2018-2019. And for the first time, a migration to the North Sea was identified on two occasions for the same shark, in summer 2018 and summer 2020.

Key words: basking shark, North-East Atlantic, public sightings, satellite tagging, movements

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Sadie Gorvett sadie.gorvett@hwdt.org Authors: Institutions

30 Years of Data Collection

Sadie Gorvett, Lauren Hartny-Mills Hebridean Whale and Dolphin Trust (HWDT), 28 Main Street, Tobermory, Isle of Mull, PA75 6NU, UK

The Hebridean Whale and Dolphin Trust (HWDT) has collated sightings data and photographs of basking sharks for the west coast of Scotland since 1992. Reports have been collected by Tobermory based whale-watch operator Sea Life Surveys and during dedicated visual surveys from HWDT’s research vessel Silurian, under license from NatureScot. Silurian has recorded a total of 1,069 sightings of 1,978 basking sharks during 112,682km of visual survey effort between 2003 and 2022. Since 2017, a total of 1,068 sightings of 2,973 basking sharks have been submitted, from land and sea, to HWDT’s community sightings network, Whale Track, a smartphone application and website with capability to submit photos.

These data have critically advanced the understanding of basking sharks in Hebridean seas, contributing to the designation of the Sea of the Hebrides as a Nature Conservation Marine Protected Area for basking sharks. They are also used to monitor and understand the conservation implications and risks of threats like entanglement.

Entanglement is the only known anthropogenic cause of mortality in basking sharks (SMASS, 2019) and they are one of the most regularly entangled marine animals in Scotland (MacLennan et al., 2021). As a founding member of the Scottish Entanglement Alliance (SEA), we assess the impact and risk of entanglement in Scottish waters, and work with fishers to trial mitigation measures.

Long-term monitoring of this nature remains our priority, ensuring we can facilitate collaboration to better understand wide-scale movements of marine animals and identify areas of importance to provide the evidence needed to inform effective conservation measures.

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Shane Wasik shane@baskingsharkscotland.co.uk Institution:

Collaborative citizen science & basking shark tourism around West Scotland

Basking Shark Scotland

Basking Shark Scotland’s first season was 2013, funded by tourism, founder Shane Wasik, wanted to have a real focus on collaborative science from the start. Over the past 11 years they have contributed to many academic projects in addition to their own, resulting in a number of publications.

Scientific collaboration with tourism is a balance, gaining access to a huge opportunity of low cost field work with motivated people. However when the public are paying to be there, the operation always needs to be mindful of their passengers expectations on how much time and resource is given over to science vs their enjoyment. Who said science isn’t fun….right!

Although data collection for traditional science has been really successful, they have found that modern technology such as drones and underwater cameras have really helped in capturing behavioural data. Site fidelity has been proven from underwater images, connections have been made between tagging projects, new behaviour has been captured and old theories challenged from new angles.

Swimming with basking sharks has always been an iconic experience and one very much centralised around the NE Atlantic coast. BSS focussed in on that as an operator and created a more stringent version of the Shark Trust’s original code of conduct. With the Shark Trust seeking to review their COC, we can share some of the learnings and critique to aide discussion on public interaction with basking sharks using lots of practical examples.

Key words: basking shark, tourism, citizen science, code of practice, conservation

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Rupert Ormond rupert.ormond.mci@gmail.com Authors: Institutions:

Basking Sharks: small mysteries in big sharks

Rupert Ormond1,2, Mauvis Gore1,2, Ewan Camplisson1 1. Centre for Marine Biodiversity and Biotechnology, Heriot-Watt University, Edinburgh 2. Marine Conservation International, South Queensferry, Edinburgh 3. School of Science, University of Manchester, Manchester

We decided to take the opportunity of the covid lockdown to make sense of our extensive notes from basking shark papers. This led to the idea of preparing an updated review on the species, a task that turned out to be much more of a challenge than we had anticipated, since perhaps inevitably some errors and misunderstandings crept in. Nevertheless, the result hopefully provides a useful overview of the species, and in particular draws attention to a number of remaining gaps in knowledge. Thus, while recent evidence strongly points to mating occurring within torus forming aggregations in high-latitude summer feeding grounds, there is no clear pointer to where pupping occurs in NE Atlantic populations, other than an unusually high number of neonates reported from the Mediterranean. The effective range of the N.E. Atlantic population also remains a key issue, since it is unclear whether population estimates based on markrecapture data refer only to UK summering animals or alternatively to that of the whole Atlantic Ocean. Also, the sensory capabilities of basking shark remain poorly defined: for example, do they use vision to focus in on prey, from what distance can they detect olfactory cues generated by zooplankton, and do they use their electro-magnetic senses to navigate during migration? In addition, it is beginning to seem likely that the impacts of both climate change and of pollution by micro-plastics on basking shark biology may be greater than perhaps anticipated. Our presentation will briefly introduce these questions.

Key words: pupping grounds, population range, olfactory cues, navigation, environmental impacts

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Session 2 - Overviews/Long term studies Simon Berrow simon.berrow@iwdg.ie

Evidence of courtship behaviour by basking sharks in Irish waters

Authors: Institutions:

Simon Berrow1,2, Richard Collins1, Ryan Davies2, David Sims3 1. Irish Basking Shark Group, Merchants Quay, Kilrush, Co Clare, Ireland 2. Atlantic Technological University, Old Dublin Road, Galway, Ireland 3. Marine Biological Association, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK

Courtship and breeding are essential life-history events for any species. For many large marine megafauna, little is known about courtship and breeding as it may occur in remote locations and at considerable depths and thus is not accessible to researchers. For basking sharks, parturition has only been observed once (on the deck of a fishing vessel) and records of newly-born sharks are extremely rare. Most knowledge of basking shark reproduction was based on examinations of dead sharks in the 1950s. Courtship, mating and breeding behaviour in basking sharks therefore is poorly understood. Breaching by basking sharks has been associated with many potential functions to the shark, but is strongly associated with courtship, especially multiple breaching events. Basking shark courtship behaviour has recently been associated with highly synchronised circling behaviour “torus”, but has only rarely been witnessed globally.

Recent recordings of multiple circling groups of basking sharks in late summer (August to September) in Ireland, coupled with frequent multiple surface breaching behaviour suggests inshore Irish waters may provide important courtship areas for this species. Here we review available evidence including sightings of small (<2m) basking sharks and multiple breaching events to explore where, and when, courtship may occur.

This review highlights the importance of coastal waters off western Ireland as critical habitats supporting key reproductive behaviours of endangered basking sharks. This has important conservation implications for a species recently been given legal protection in Ireland under the Wildlife Act. This knowledge can inform marine spatial planning from the designation of Marine Protected areas to mitigation of expanding offshore renewables.

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Jess Rudd jr646@exeter.ac.uk

Spying on the secret lives of basking sharks

Authors:

Rudd JR1, Bartolomeu T2, Dolton H3, Exeter O4, Henderson SM5, Kerry C4, Kukulya A6, Shirley M7, Whelan S6, Witt MJ1, Yoder N6, Hawkes LA1 1. University of Exeter, Faculty of Health & Life Sciences, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK 2. CEiiA, Matosinhos, Portugal 3. IRELAND 4. College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn TR10 9FE, Cornwall, UK 5. NatureScot, Great Glen House, Leachkin Road, Inverness IV3 8NW, UK 6. Oceanographic Systems Laboratory, Woods Hole Oceanographic Institution, 86 Water St., Woods Hole, MA 02543, USA 7. MrROV, Wadebride, Cornwall, United Kingdom

Institutions:

A wide range of biologging technologies make it possible to understand the movements and behaviours of a huge range of animals, including basking sharks, but rarely give any insights into the context for movement and behavioural decisions. We took advantage of the huge body size of basking sharks to deploy custom-made tracking cameras of two types to gain greater insight into basking shark ecology in northwest Scottish waters. We deployed (i) towed cameras (n=6 sharks) and (ii) custom transponder tags coupled with an autonomous following and filming vehicle (n=3 sharks) onto sharks during summer months off the islands of Coll and Tiree. We gained insights such as early morning group behaviour, breaching, and surprisingly more time spent near the seabed (various types) not feeding than expected since this aggregation of sharks is thought to gather in Scottish waters to profit from seasonally abundant plankton prey. The data together suggest that the Sea of the Hebrides might be important for other life history processes such as courtship and breeding. The area was designated a Marine Protected Area in 2020 and continues to play an important role in basking shark conservation.

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Chelsea Gray Graychelsea13@gmail.com Authors: Institutions:

An Individual-Based Model of Basking Sharks in Ireland

Chelsea Gray1, Dale Rothman2, Erin Peters-Burton2, Cynthia Smith2, Chris Parsons3, Alexis Garrettson4 1. Irish Basking Shark Group, Ireland 2. George Mason University, USA 3. University of Glasgow, UK 4. Tufts University

While basking sharks are largely solitary, they gather in mixed sex aggregations, which can range from two sharks, up to 1,398 individuals. Aggregations may be related to food availability, though some observational evidence suggests feeding is not the sole reason for this behavior. As basking sharks feed on zooplankton at the surface of coastal water, these aggregations can pose a threat to boaters and the sharks themselves.

An individual-based model (IBM) of basking sharks in Inishowen, Ireland, was created in Netlogo. The IBM incorporates zooplankton data from the Continuous Plankton Recorder and localized patchiness of zooplankton on a small scale was simulated. Tests of different shark behavior (only seeking food, only seeking other sharks, a combination of both behaviors) were simulated for 1982-2018. The frequency of shark aggregations and average monthly size of aggregations in the model were compared to sightings data collected by the Irish Whale and Dolphin Group (IWDG) and Irish Basking Shark Group (IBSG).

Simulated aggregations were significantly more likely to match observations collected by the IWDG/IBSG when both seeking food, but also, in select cases, when seeking other sharks. This indicates that aggregations may be significant for both reproduction and food intake. These findings agree with previous research and indicate the need for protective measures in these areas when basking sharks are likely to congregate.

This is the first IBM of basking shark behavior and demonstrates the usefulness of such simulation methods for understanding the behavior of semi-solitary, migratory shark species such as these. Key words: Individual-based model; Ireland; Simulation; Aggregations; Behavior.

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Haley Dolton Body temperature dynamics of basking sharks doltonh@tcd.ie Authors:

Institutions:

Haley R. Dolton1, Andrew L. Jackson1, David E. Cade2, Taylor K. Chapple3, Mason N. Dean4, David Edwards5, Jeremy A. Goldbogen2, Alexandra G. McInturf3, Edward P. Snelling6, Nicholas L. Payne1 1. Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin D02 PN40, Ireland 2. Oceans Department, Hopkins Marine Station, Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA 3. Coastal Oregon Marine Experiment Station, Oregon State University, Newport, OR, USA 4. Department of Infectious Diseases & Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Hong Kong, China 5. West Cork Charters, Shannonvale, Clonakilty, Co. Cork, P85 FV00, Ireland 6. Department of Anatomy and Physiology, and Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0028, South Africa

The planktivorous basking shark Cetorhinus maximus is closely related to athletic white sharks Carcharodon carcharias and shortfin mako sharks Isurus oxyrinchus than other filter-feeding shark species such as the whale shark Rhincodon typus. It was widely assumed that basking sharks shared the anatomy and physiology of fully ectothermic fishes, but we now know they have anatomical traits associated with regional endothermy and an elevated subcutaneous white muscle temperature above ambient. As the first filter-feeding regionally endothermic shark, the basking shark represents a unique model to study the rate of heat exchange through heat transfer coefficient estimation (HTC). Here we show that basking sharks cool down faster than predicted for their mass and cool down approximately 100 times faster than the entire biologging timeseries after bouts of increased mechanical effort. The higher HTC estimation than predicted for their mass could possibly be caused by their filter-feeding life history and suggests the purpose of regional endothermy in basking sharks may facilitate feeding in cold waters. Key words: Regional endotherm, ectotherm, heat transfer coefficient, filter-feeding, heat exchange.

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Session 3 - Spatial Ecology & Policy Peter Miller pim@pml.ac.uk

Ocean fronts and stratification influence the distribution of basking sharks and marine biodiversity

Institution:

Plymouth Marine Laboratory, Prospect Place, The Hoe, PL1 3DH, Plymouth, UK

Fronts – the boundaries between water masses – are hotspots for rich and diverse marine life, with particular influence on the foraging distribution of basking sharks. Many shelf-sea fronts indicate the horizontal extent of seasonal stratification of the water column, a process that balances the effects of solar heating and wind mixing and hence may alter with climate change. Understanding these oceanographic processes is important for effective conservation of shark populations. We previously quantified the influence of thermal and chlorophyll-a fronts on basking shark habitat use in the northeast Atlantic using satellite data, both over seasonal timescales and in near real-time. We are developing a new global dataset of thermal fronts at 5km resolution, and linking this with ocean colour to generate dynamic ‘biophysical seascapes’ with the aim to explain the distribution of pelagic marine biodiversity and assist in optimising high-seas protected areas. This is within the European Space Agency project Biodiversity in the Open Ocean: Mapping, Monitoring and Modelling (BOOMS: booms-project.org). We encourage collaboration with ecologists who may benefit from relating tagged animal tracks to these ocean front datasets and seascapes.

Key words: oceanic fronts; remote sensing; basking sharks; seascapes; biodiversity.

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Claudia Junge & Antonia Klöcker claudia.junge@hi.no antonia.kloecker@hi.no Authors:

Institutions:

On The Edge – Deciphering Distribution And Movement Patterns Of Basking Sharks In The Arctic

Antonia Klöcker1, Kristina Ø Kvile2, Ferter Keno1, Bjelland Otte1, Mikko Vihtakari1, Morten D. Skogen1, Jon Albretsen1, Claudia Junge1 1. Institute of Marine Research (IMR), Norway 2. Norwegian Institute for Water Research (NIVA), Norway

The distribution of basking sharks (Cetorhinus maximus) is described as patchy and strongly driven by sea surface temperature and food availability, in temperate waters. Yet, for their northern distribution edge, we lack fundamental information on hotspots and spatio-temporal habitat use, as well as relevant environmental drivers and potential temporal trends. Species distribution models can here provide a powerful tool to investigate how environmental factors influence shark occurrence over annual and sub-annual time scales.

We collected over 500 observations mainly through IMR’s citizen science online platform “Dugnad for Havet” and the shark hotline. We achieved a huge public engagement and found seasonally variable hotspots of basking shark occurrence in Norwegian waters. We inspect possible drivers and discuss possible distributional changes over time. With climate change set to alter conditions in northern latitudes at the range edge of this species, this knowledge is pivotal to contrast with existing data from more central areas of the shark’s distribution. Most of the research has so far focussed on surface-based observations and existing telemetry studies were commonly restricted seasonally in the North Atlantic. Deploying satellite tags on animals inhabiting Arctic waters north of the polar circle in the boreal summer for up to 365 days, we want to understand how diverse and extreme habitats in terms of temperatures and light regimes influence the movement and diving behaviour of basking sharks in the Northeast Atlantic. Combined, our results will contribute to better understand inter-annual habitat use, potential drivers, impact of climate change, and exposure to threats.

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Jonathan Houghton j.houghton@qub.ac.uk

Basking Sharks: Lessons from the EU SeaMonitor Programme (2019-2023)

Authors:

J.D.R. Houghton1,2, J.T. Thorburn1,3, A. Garbett1,2, P.J. Mensink4, E.J. Johnston1,2, P.C. Collins1,2 Institutions: 1. School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, Co. Antrim Northern Ireland, BT9 7DL 2. Queen’s University Marine Laboratory, 12-13 The Strand, Portaferry, Co. Down, Northern Ireland, BT22 1PF 3. Edinburgh Napier University, School of Applied Sciences, Edinburgh, Scotland.

4. The University of Western Ontario, Centre for Environment and Sustainability, 253 North Campus Building, London, Ontario, Canada, N6A 5B7 SeaMonitor was a four-year research project culminating in March 2023, focused on the seas around Ireland, Western Scotland and Northern Ireland. The €4.6M project was led by the Loughs Agency and supported by another eight marine research institutions using a range of tracking technologies to understand and protect vulnerable marine life across jurisdictional boundaries (i.e., seals, flapper skate, basking sharks, salmon and cetaceans). Queen’s University Belfast, the Irish Marine Institute and Western University Canada gathered movement and diving data on basking sharks to inform potential management plans on a regional scale.

During the forum we will report on three key deliverables from SeaMonitor: (i) Assessing the connectivity of basking shark hotpots via acoustic and satellite telemetry; (ii) Building predictive models of basking shark surfacing behaviour in coastal hotspots; (iii) Developing the analytical framework for a basking shark collision avoidance tool (CAT) to support stakeholder engagement and management. Collectively, these findings reinforce the need for a regional approach to species management, with a close alignment to policy and conservation measures between the relevant nations.

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Rona Sinclair

Future Directions – NatureScot perspective

Authors:

Rona Sinclair (Rona.Sinclair@nature.scot) Suz Henderson (Suzanne.Henderson@nature.scot) NatureScot

Institution:

Valuable data collection and collaboration has been instrumental in providing the evidence to support the designation of the Sea of the Hebrides MPA in 2020, with basking sharks as a protected feature. Our future work on basking sharks sits within the backdrop of elasmobranch actions within the draft Scottish Biodiversity Strategy delivery plan, finding efficiencies and priorities for our statutory obligations and the Scottish MPA monitoring strategy.

Key words: Basking sharks, MPAs, monitoring, reporting

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Session 4 - Data & Collaboration Harriet Allen harriet@sharktrust.org

Historic data management: challenges and future directions

Institution:

The Shark Trust

Citizen Science led Basking Shark data has been collected over a course of decades, by multiple organisations and multiple different methods. Due to this, the types and quantity of metadata from citizen science projects can differ greatly. The Shark Trust are custodians of the Marine Conservation Society’s Basking Shark Watch database, as well as the data from our own Basking Shark Project. Combining datasets from different sources comes with unique challenges both in terms of data management and data interpretation. Going forward we wish to discuss the key uses for this data and, therefore, the most suitable ways of managing, interpreting and sharing this data.

Key words: Data management, collaboration, data sharing, historic

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Matthew Witt M.J.Witt@exeter.ac.uk Authors: Institutions:

A new acoustic telemetry network for basking sharks in NW Scotland Hawkes LA1, Garzon F1, Henderson SM2, Witt MJ1 1. University of Exeter, Faculty of Health & Life Sciences, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK 2. NatureScot, Great Glen House, Leachkin Road, Inverness IV3 8NW, UK

The waters of northwest Scotland (the Sea of the Hebrides) are a regional hotspot for basking sharks, which occur there in the summer months from July to October. Previous satellite tracking has shown that there is a particularly well visited area between the islands of Coll and Tiree (Gunna Sound), and that they return to this area between years. Consequently, in 2020, a Marine Protected Area was established for the conservation of basking sharks (and minke whales), although the area is also an important site for other cetacean and sea bird species. Basking sharks are often observed foraging at the waters’ surface in the Sea of the Hebrides, but it is unclear whether they visit Scottish waters purely to feed on seasonally abundant copepod prey, or whether waters there may serve a secondary function such as aggregation for courtship or breeding, and whether they occur there in other months of the year, spending time away from detection at the surface. Although great gains have been made in understanding basking shark ecology, most tracking tags can only record data for about a year. Therefore, in May 2022, a network of 10 acoustic receivers was installed around Gunna Sound. In 2023, 20 basking sharks were tagged with Vemco V16 acoustic tags, with a 10-year battery life. Initial data reveal 9 of these sharks have been detected by the acoustic receivers, with one shark being detected as late as December 2023. The receiver array has also detected basking sharks tagged in Ireland. A further 25 sharks will be tagged in 2024.

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Kristina Øie Kvile kristina.kvile@niva.no

Save Our Shark: how to realise policy change

Authors:

Kristina Øie Kvile1, Antonia Klöcker2, Mikko Vihtakari2, Claudia Junge2 1. Norwegian Institute for Water Research (NIVA), Grimstad, Norway 2. Havforskningsinstituttet (Institute of Marine Research, IMR), Tromsø, Norway

Institutions:

The endangered basking shark (Cetorhinus maximus) is experiencing pressure from fisheries, coastal development, and climate change. To ensure effective conservation measures and management, knowledge about the species’ distribution is key. Yet, fundamental information about its habitat use is lacking, increasing the vulnerability to human activities, particularly at the edges of its range. The Norwegian coast is part of the northern range of basking sharks. While no systematic survey of basking sharks exist in this area, observations of basking sharks in surface waters have been compiled as part of a national citizen science project called ‘Dugnad for havet’. Here, we will show predicted basking shark hotspots along the Norwegian coast under present and future climate. The results are based on Boosted Regression Tree models linking the citizen science observations to openly available environmental data from Bio-ORACLE. As next steps, the models will be refined with higher-resolution data for targeted environmental drivers. Ultimately, these results will allow us to investigate the co-occurrence of distributional hotspots with current and future human activities and highlight areas of elevated scientific and management importance at the northern edge of the species’ distribution in the light of competing management priorities and a changing climate.

Key words: distribution model, citizen science, environmental drivers, climate change, Bio-ORACLE

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James Thorburn Presenting author: j.thorburn2@napier.ac.uk Lead author: j.houghton@qub.ac.uk Authors:

Assessing the potential of acoustic telemetry to underpin the regional management of basking sharks (Cetorhinus maximus)

Thorburn J, Collins PC, Garbett A, Vance H, Phillips N, Drumm A, Cooney J, Waters C, Ó’Maoiléidigh N, Johnston E, Dolton HR, Berrow S, Hall G, Hall J, Delvillar D ,McGill R, Whoriskey F, Fangue NA, McInturf AG, Rypel A, Kennedy R, Lilly J, Rodge, JR, Adams CE, van Geel NCF, Risch D, Wilkie L, Henderson S, Mayo PA, Mensink, P, Witt MJ, Hawkes LA, Houghton, JDR

This study pioneers the use of acoustic telemetry to monitor basking sharks (Cetorhinus maximus), a species of high conservation concern, in the coastal waters of Ireland, Northern Ireland, and Scotland. Acoustic telemetry, a valuable tool for tracking marine species, faces challenges in deploying species-specific arrays over vast areas for highly migratory vertebrates. To address this issue, we investigated the feasibility of utilising broadscale, multiproject acoustic receiver arrays as a cost-effective platform for cross-border monitoring of basking sharks to inform the development of a cross-jurisdiction management strategy for this species. Throughout 2021 and 2022, we tagged 35 basking sharks with acoustic transmitters off the west coast of Ireland; 27 of these were detected by 96 receiver stations throughout the study area (n=9 arrays) with up to 216 detections of an individual shark (mean = 84, s.d. 65). On average, sharks spent ~one day at each acoustic array, with discrete residency periods of up to nine days. Twenty-one sharks were detected at multiple arrays with evidence of inter-annual site fidelity with the same individuals returning to the same locations in Ireland and Scotland over two years. Eight pairs of sharks were detected within 24 hours of each other at consecutive arrays, suggesting some level of social coordination and synchronised movement. These findings demonstrate that acoustic telemetry can support multi-jurisdictional monitoring for basking sharks and other highly mobile species. To achieve this goal, there is a necessity for collaborative efforts across jurisdictions to establish the required infrastructure and to secure ongoing support.

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Alexandra McInturf agmcinturf@gmail.com

Return of the shark: Conservation insights from 50 years of basking shark (Cetorhinus maximus) sightings in Irish waters

Authors:

Alexandra G. McInturf1,2,3, Chelsea Gray1, Natasha D. Phillips1, Caroline Lynam1, Donal C. Griffin1, Samhita Vinu-Srivatsan4, Padraig Whooley5, Nick Massett5, Simon Berrow1,5,6, Lucy Hunt5,7, Emmett M Johnston1,8

Institutions:

1.

2.

3.

4.

5.

6.

7.

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Irish Basking Shark Group, Co. Donegal, F93 P6K5, Ireland Coastal Oregon Marine Experiment Station, Oregon State University, Newport, OR USA Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, OR USA Monta Vista High School, Cupertino, CA 95014 Irish Whale and Dolphin Group, Merchants Quay, Killrush, Co. Clare, Ireland Atlantic Technological University, Old Dublin Road, Galway, Ireland Sea Synergy, Cahersiveen, Co.Kerry, V23 Y925 National Parks and Wildlife Service, Department of Housing, Local Government and Heritage, 90 King Street North, Dublin 7, Ireland

The basking shark is a notable omission from the EU Habitats Directive and is the first fish to receive legal protection in Ireland under domestic wildlife legislation. This action was underpinned by the documented importance of Irish waters for the species and a publicly perceived increase in basking shark sightings here. In this study, we examined long-term patterns in Irish basking shark sightings using 50 years of community science data. Furthermore, we generated a species distribution model for basking sharks in this region to determine the link between shark sightings and environmental variables that have been linked to the occurrence of sightings (e.g. SST, chl-a, North Atlantic Oscillation (NAO)). Our analysis revealed a notable increase in shark sightings (from a mean of 53 to 388 sharks/ year) and group size (from a mean of 3.4 to 4.0 sharks/group) in Ireland after 2000.

We also observed a significant response to sea surface temperature, primary productivity, and NAO. Finally, we found quantitative support for seasonal and latitudinal movement, with the highest probability of sightings throughout Ireland in March through June, and along the southern coast during spring/fall and the northern coast in summer months. Ultimately, our study yields important insights into whether and why basking sharks continue to aggregate at the surface in Irish waters. These findings contrast sharply with declining reports in other surface hotspots where paradoxically, conservation efforts are more established and advanced. Understanding such patterns is a prerequisite to establishing effective trans-boundary protective measures for this wide-ranging species. Key words: hotspots, population trends, policy, Ireland, endangered species

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Acknowledgements The Shark Trust would like to thank all the contributors to the Basking Shark Forum 2024, and to acknowledge all those who work in research and conservation of Chondrichthyan fishes. We especially thank all the funders past and present which includes (but is not limited to) Save our Seas Foundation, The Peter Scott Trust for Education and Research in Conservation, Project AWARE, The Marine Conservation Society WWF & Ken Watterson. The Shark Trust also acknowledges the supporters of the Basking Shark Adoption Programme whose generosity continues to assist conservation activities.

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©Andrew Pearson

Basking Shark Forum 2024

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