Scholarly article on topic 'Testing the boundaries: Seasonal residency and inter-annual site fidelity of basking sharks in a proposed Marine Protected Area'

Testing the boundaries: Seasonal residency and inter-annual site fidelity of basking sharks in a proposed Marine Protected Area Academic research paper on "Biological sciences"

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Biological Conservation
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{"Animal movement" / " Cetorhinus maximus " / Conservation / "North-east Atlantic" / "Satellite tracking"}

Abstract of research paper on Biological sciences, author of scientific article — P.D. Doherty, J.M. Baxter, B.J. Godley, R.T. Graham, G. Hall, et al.

Abstract There is a growing need to understand the inter-annual movements of mobile marine species of conservation concern to inform the design and placement of Marine Protected Areas (MPAs) to maximise their conservation potential. We use satellite telemetry data from 36 basking sharks (Cetorhinus maximus) tracked in 2012, 2013 and 2014 (cumulative total: 1598days; median: 44days; range: 10–87days) to quantify movements in coastal waters off the west coast of Scotland within the Sea of the Hebrides proposed MPA. Sharks exhibited seasonal residency to the proposed MPA, with a mean of 84% of filtered best daily locations occurring within its boundaries (2012=80%, 2013=90% and 2014=74%). Three long-term tracked basking sharks demonstrated inter-annual site fidelity, returning to the same coastal waters in the year following tag deployment, with two returning to within the boundaries of the proposed MPA. These data likely suggest the area experiences favourable conditions and/or resources for basking sharks across years and, if designated, coupled with appropriate management, could afford protection during summer months.

Academic research paper on topic "Testing the boundaries: Seasonal residency and inter-annual site fidelity of basking sharks in a proposed Marine Protected Area"


Testing the boundaries: Seasonal residency and inter-annual site fidelity of basking sharks in a proposed Marine Protected Area

P.D. Doherty a'b, J.M. Baxterc, B.J. Godley a'b, R.T. Graham d, G. Halle, J. Halle, L.A. Hawkes b, S.M. Hendersonf, L. Johnson g, C. Speedie g, M.J. Witta'*

a Environment and Sustainability Institute, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK b Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK c Scottish Natural Heritage, Silvan House, 231 Corstorphine Road, Edinburgh EH12 7AT, UK d MarAlliance, PO Box 283, San Pedro, Ambergris Caye, Belize

e Manx Basking Shark Watch, Glen Chass Farmhouse, Glen Chass, Port St Mary IM9 5PJ, Isle of Man f Scottish Natural Heritage, Great Glen House, Inverness, Scotland IV3 8NW, UK g Wave Action, 3 Beacon Cottages, Falmouth TR11 2LZ, UK


There is a growing need to understand the inter-annual movements of mobile marine species of conservation concern to inform the design and placement of Marine Protected Areas (MPAs) to maximise their conservation potential. We use satellite telemetry data from 36 basking sharks (Cetorhinus maximus) tracked in 2012, 2013 and 2014 (cumulative total: 1598 days; median: 44 days; range: 10-87 days) to quantify movements in coastal waters off the west coast of Scotland within the Sea of the Hebrides proposed MPA. Sharks exhibited seasonal residency to the proposed MPA, with a mean of 84% of filtered best daily locations occurring within its boundaries (2012 = 80%, 2013 = 90% and 2014 = 74%). Three long-term tracked basking sharks demonstrated inter-annual site fidelity, returning to the same coastal waters in the year following tag deployment, with two returning to within the boundaries of the proposed MPA. These data likely suggest the area experiences favourable conditions and/or resources for basking sharks across years and, if designated, coupled with appropriate management, could afford protection during summer months.

© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license



Article history:

Received 2 August 2016

Received in revised form 16 January 2017

Accepted 25 January 2017

Available online xxxx

Keywords: Animal movement Cetorhinus maximus Conservation North-east Atlantic Satellite tracking

1. Introduction

With global declines in many marine fish populations and habitats (Watson and Pauly, 2001; Baum et al., 2003; Lotze et al., 2006) the use of Marine Protected Areas (MPAs) has become increasingly popular as a management tool to prevent further population decline, promote recovery and improve biodiversity conservation (Halpern and Warner, 2002; Wood et al., 2008). Studies have suggested that large, mobile species, with wide-ranging movements may benefit from MPAs, e.g. teleost fish (Farmer and Ault, 2011), turtles (Scott et al., 2012), whales (O'Brien and Whitehead, 2013), as well as sharks (Claudet et al., 2009; Barnett et al., 2011), depending on protective measures applied to these areas.

In particular, there is growing concern regarding the rate of decline of global shark populations due to overfishing (Dulvy et al., 2014). The proportion of time individuals spend within MPA boundaries will affect the degree to which these animals could be protected, should adequate

* Corresponding author at: Environment and Sustainability Institute, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK.

E-mail addresses: (P.D. Doherty), (M.J. Witt).

management measures also be in place. This protection is likely to vary with species, life stage, sex, size, body condition and food availability (Speed et al., 2010; Escalle et al., 2015). Designing MPA boundaries and management measures to be effective for mobile species require detailed knowledge of the species' biology, movements and habitat use (Gruss et al., 2011; Chin et al., 2016). Establishing MPAs in areas that mobile species use consistently (e.g. areas of key life-history events) may offer some protection at a population level (Heupel and Simpfendorfer, 2005; Meyer et al., 2007), and protection will therefore depend on the degree of overlap between core activity areas and the area of protection (Knip et al., 2012).

Basking sharks were historically exploited in the north-east Atlantic for their meat, fins and large liver containing desired squalene oil; with directed fisheries from Norway, Scotland and Ireland. These fisheries landed 77,204 individuals between 1946 and 1986 (Kunzlik, 1988), leading to depletion in local stocks (Parker and Stott, 1965). Basking sharks are listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), Appendices I and II in the Convention of Migratory Species (CMS; Table S1), and are listed as 'Vulnerable' globally by the International Union for Conservation of Nature (IUCN Red List), and 'Endangered' in the north-east

0006-3207/© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (

Atlantic (Fowler, 2005). The Marine (Scotland) Act (2010) and the UK Marine and Coastal Access Act (2009) include powers for Scottish Ministers to designate MPAs in the seas around Scotland, one of which is the proposed 10,325 km2 Sea of the Hebrides MPA, between the Isles of Skye, Mull and Outer Hebrides (Scottish Natural Heritage, 2014). This area has been highlighted as a key area for surface sightings of basking sharks (Speedie et al., 2009; Witt et al., 2012) between July and August each year, and for minke whales (Balaenoptera acutorostrata) and was thus proposed for designation as a MPA (Scottish Natural Heritage, 2014).

In an attempt to increase protective measures for marine environments and to satisfy international conventions, many MPAs have been implemented opportunistically without prior knowledge of how they may contribute to biodiversity conservation (Roberts, 2000). Assessment of the efficacy of a MPA is important in order to maximise its conservation potential (McNeill, 1994), otherwise there is a possibility of tokenism if placed arbitrarily (Ashe et al., 2010). We used satellite tags in order to (1) describe the seasonal (summer months) space-use of coastal waters off the west coast of Scotland by basking sharks, (2) describe areas of inter- and intra-annual density and (3) evaluate the use of the Sea of the Hebrides proposed MPA and establish the amount of time sharks spent inside the proposed MPA thus quantify the potential importance of this area to basking sharks.

2. Materials & methods

2.1. Tag attachment and specification

Sixty-two satellite tags, communicating with the Argos System, were attached to basking sharks off the west coast of Scotland during July and August in 2012, 2013 and 2014. Basking sharks were approached by boat from behind to avoid the line of sight of the shark and to minimise disturbance. On approach to the shark, the individual was, where possible, sexed using a pole mounted camera and total body length was estimated based on comparison to the total length of the boat (10 m). Satellite tags were deployed using a titanium M-style dart (Wildlife Computers, Redmond, California, USA) inserted into the sub-dermal layer at the base of the first dorsal fin with a modified pole spear and attached via a tether consisting of heat-shrink covered stainless steel flexible cable, a swivel and monofilament line attached to the tag. Four models of satellite tags were deployed to gather a variety of information on the movements and distribution of tagged animals. Thirty-six satellite tags were used in this analysis; Smart Position or Temperature tags (SPOT; n = 23, Wildlife Computers, Redmond, California, USA) and SPLASH-F tags (n =13, Wildlife Computers, Redmond, California, USA) and transmitted data in real-time while attached to study animals. Both tag models provided Argos Doppler-based estimates of location (termed Argos locations) during shark surfacing events. SPLASH-F tags also contained Fastloc™ GPS technology, providing GPS locations in addition to collecting light, temperature and depth data. Both, Argos and GPS locations were used for analysis of summer movement patterns and seasonal site fidelity. Remaining tags that transmitted data (n = 24) were Pop-up Archival tags fitted with Fastloc™ GPS technology (PAT-F; n = 12) and MiniPAT (n = 12; Wildlife Computers, Redmond, California, USA). These tags were used to gather information on longer-range movements of basking sharks away from the west coast of Scotland using the principles of light geolocation (Doherty et al., 2017).

2.2. Location data processing

Analysis focused on coastal movement within the summer months; therefore, data were confined to 90 days (approx. mid July-mid October) following tag deployment and prior to the departure of sharks from the region. Data from satellite tags transmitting in the year following tag attachment were examined to ascertain inter-annual site

fidelity. Argos location data from SPOT tags were subject to filtering, retaining location classes 1 (accurate to 500-1500 m), 2 (accurate to 250-500 m), 3 (accurate to <250 m), 'A' (three messages received but no accuracy estimation) and 'B' (one or two messages received but no accuracy estimation) (Witt et al., 2010). GPS location data from SPLASH-F tags deployed in 2014 were filtered to include only positions with a residual error value of < 30 and where five or more satellites were visible to estimate the location (Shimada et al., 2012). GPS locations from SPLASH-F tags in 2014 were favoured over Argos locations from the same tags as the number of GPS locations was more numerous (662 vs. 463 Argos locations; post-filtering) and GPS locations have a greater spatial accuracy (Table S2). A maximum plausible speed filter was applied to both datasets removing locations if speed between two locations exceeded 10 km h-1. These data were later reduced to a single, most accurate best daily location (highest location class as described above for Argos locations and maximum number of visible satellites for GPS locations) to minimise spatial and temporal autocorrelation. All tag data were downloaded from CLS-Argos and archived using the Satellite Tracking and Analysis Tool (STAT) (Coyne and Godley, 2005).

2.3. Data analysis

We used four techniques to identify core activity areas of residency, these techniques were; Minimum Convex Polygons (MCPs), polygon sampling grid, Time Local Convex Hulls (T-LoCoH) and Kernel Density Estimation (KDE). MCPs create the smallest convex polygon that incorporates all filtered best daily locations. To determine areas of high relative importance, a polygon sampling grid (hexagonal cells; 2 km from each grid cell centroid to its perimeter; cell area 14 km2) was spatially intersected with filtered best daily locations. The proportion of locations within each grid cell was calculated for each tracked shark; a mean proportion for each cell was then calculated. We used T-LoCoH to construct utilisation distributions by aggregating local MCPs around each point, which were then sorted and progressively merged to form isopleths. Local Convex Hull (LoCoH) methods have been shown to outperform traditional kernel-smoothing techniques in excluding areas known not to be used (Getz et al., 2007). These attributes make LoCoH methods applicable to analyse collective area use of multiple individuals. T-LoCoH offers an advantage over traditional approaches because it further improves the ability to partition area use and study patterns through time (Lyons et al., 2013). We applied the k-based method with no time-based weighting, constructing hulls for defined numbers of neighbouring points due to the absence of areas with high density of clustering as well as areas of sparsely distributed points (Lyons et al., 2013). We also applied KDE interpolation with barriers as described by Macleod (2014). KDE with barriers uses the shortest distance between points without intersecting a defined barrier, in this case land, allowing the contour of the kernel to change at the edge of the barrier (Sprogis et al., 2016). Output cell size was 250 m side length and the bandwidth (search radius) was 5000 m. The bandwidth is a smoothing value that determines the width of the kernel. Choice of bandwidth method may vary depending on the study goals, sample size and patterns of space use by the study species (Gitzen et al., 2006), therefore the bandwidth value was selected by iterative visual inspection of outputs and evaluating the results based on extant ecological knowledge of the species.

Individual trajectories of tracked basking sharks were separated into groups based on movements relative to the boundaries of the proposed MPA using k-means cluster analysis (Hartigan and Wong, 1979). Individual tracks were initially separated into High-use (n = 29) and Low-use (n = 7) groups based on time spent within the boundaries of the proposed MPA. To ascertain the use of the proposed MPA, movements of tracked basking sharks the High-use group was further split into Near (n = 23) and Far (n = 6) groups based on their maximum displacement distances from tagging location.

Data analysis was performed in R (RCore Team, 2014), with satellite tag location filtering applied using the adehabitat packages (Calenge, 2006) and T-LoCoH analysis using the T-LoCoH package (Lyons et al., 2013). All spatial analyses and maps were created using Geospatial Modelling Environment (GME v; Beyer, 2012) and ESRI ArcMap 10.1.

3. Results

The movements of 36 basking sharks were analysed comprising eight males, 11 females and 17 of unknown sex. Sharks ranged from four to eight metres in length (4-5 m, n = 4 sharks; 5-6 m, n = 15 sharks; 6-7 m, n = 8 sharks and 7-8 m, n = 9 sharks). Sharks were tracked for a cumulative summer duration of 1598 days (mid. July-mid. October; median: 44; range: 10-87 days), moved a median minimum along-track straight-line distance of 353 km (Inter-Quartile Range (IQR): 260 km range: 111-1410 km; Table S2) and were displaced a median 63 km (IQR: 71 km; range: 23-167 km) during

that time. Following summer movements, 20 of these sharks were tracked departing the region (Doherty et al., 2017).

Tracked basking sharks demonstrated three movement behaviours throughout the summer (Fig. 1; Figs S1-3), which was independent of tracking duration within the period (GLMM; x2i = 2.07, p = 0.15); here, defined as (1) High-use and near, where sharks remain close to tagging location around the coastal waters of the Isles of Coll and Tiree within the boundaries of the proposed MPA (n = 23; Fig. 1B), (2) High-use and far, where sharks are mobile, using a high proportion of space within the proposed MPA, but away from tagging location, (n = 6; Fig. 1C) or (3) Low-use, where sharks leave the boundaries of the proposed MPA (n = 7) either permanently or re-entering at a later date within the same summer season (Fig. 1D).

Minimum Convex Polygons (MCPs) of tracked basking sharks across years reached from the tagging location and proposed MPA southwards to the coasts of Ireland and Northern Ireland, encompassing the waters off the Isles ofJura and Islay, west of the Outer Hebrides. The boundaries circumscribed areas of 21,182 km2 in 2012, 24,532 km2 in 2013, and

Fig. 1. Movement of tracked basking sharks in summer months (2012-2014; mid-July- to mid-October). (A) Study area; west coast of Scotland, showing proposed MPA (grey polygon). Examples of individual tracks that exemplify three modes of movements: (B) High-use and near, where sharks remain close to tagging location within the boundaries of the proposed MPA (n = 23), PTT137654 shown as example; (C) High-use and far, where sharks are mobile, using a high proportion of space within the MPA away from tagging location, PTT129449 shown as example (n = 6); (D) Low-use, where sharks leave the boundaries of the proposed MPA PTT 129441 shown as example (n = 7). White stars denote tag deployment, black stars denote track end point for the summer months. Solid line is representative of tracked movement. Economic Exclusive Zone (EEZ) between UK and Ireland (dashed grey line).

9403 km2 in 2014. In 2014, Argos and GPS locations were available from SPLASH-F tags, the MCP from Argos locations was 8641 km2 for Argos locations as compared to 9403 km2 for GPS, we chose to use GPS locations in further analysis due to their greater volume, and hence likely improved chance to more accurately describe the occupied MCP in that season. The mean MCP areas of tracked sharks was 2605 km in 2012, 3154 km in 2013 and 3258 km in 2014 (applied to GPS locations compared to 1221 km2 for Argos locations) (Table 1; Fig. 2A). The majority of filtered best daily locations (84%) occurred within the boundaries of the proposed MPA across all years (mean value, 2012 = 80%, 2013 = 90% and 2014 = 74%; Table 1, Figs 2A and S1-3). Grid density plots highlighted two common areas of high occupancy; to the southwest of the Isle of Coll, and between the islands of Coll and Tiree, an area known as Gunna Sound (Fig. 2B). These areas were further identified using T-LoCoH and Kernel Density analysis, which show the extent of use of these hotspots. The approaches identified other areas to the north, in waters of the Isles of Hyskeir and Canna. Core activity areas were almost entirely encompassed within the proposed MPA boundaries (T-LoCoH 50% isopleth = 91%, KDE 50% contour = 97%).

Five basking sharks were tracked for longer than a year (>365 days), and three of these sharks returned to the waters off the west coast of Scotland from over-wintering grounds the subsequent summer permitting insights into inter-annual site fidelity. The remaining two sharks were tracked in coastal waters off the west coast of Ireland the subsequent summer. The three returning sharks dispersed 565, 304 and 1474 km (minimum straight-line distance) from tag attachment location, these distances occurring in April, December and April respectively, and then returning to within 29, 138 and 24 km of the centroid of their core activity area from the first year of tracking respectively (Fig. 3). Two sharks returned to the waters of the proposed MPA in both years (Fig. 3A and C); the third shark was located outside the MPA boundary in the second year of tracking (Fig. 3B, Table S3).

4. Discussion

The need to identify key areas of activity of large marine vertebrates in coastal areas is essential in order to appropriately delineate areas, and their boundaries, where protection measures can be implemented. MPAs can benefit mobile marine species (Worm et al., 2003), including cetaceans, pinnipeds, sea otters, sea birds, sharks, cephalopods, and tel-eost fish (Hooker and Gerber, 2004). Our study showed that satellite tracked basking sharks in the north-east Atlantic exhibited seasonal residency and inter-annual site fidelity during summer months to a proposed MPA. The study area has been recognised as a basking shark aggregation site in the summer months from public sightings data (Southall et al., 2005; Witt et al., 2012) and boat-based, effort-corrected surveys (Southall et al., 2005; Speedie et al., 2009) where foraging behaviour can be observed (Matthews and Parker, 1950; Berrow and Heardman, 1994), but thus far high-resolution tracking data has been lacking.

4.1. Near real-time tracking - Argos locations & GPS

The ability to observe fine-scale movements of marine species of conservation concern provides novel insights into horizontal movements that cannot be gained from more traditional boat-based or aerial surveys (Westgate et al., 2014). Describing these movements has provided insight into home-ranges, core activity areas and seasonal use of distinct habitats, such as tiger sharks seasonally feeding on fledgling Albatross (Phoebastria spp.) at the French Frigate Shoals and subsequent migration once this resource is depleted (Meyer et al., 2010), and large-scale migrations of leatherback turtles (Dermochelys coriacea) from Central Africa (Witt et al., 2008). More recently, the development of Fastloc™ GPS technology in telemetry allows highly accurate locations to be acquired from very brief (millisecond) surfacing events. This has led to high-resolution coastal water use by reef manta rays (Manta alfredi; Braun et al., 2014) and whale sharks (Rhincodon typus; Berumen et al., 2014). Such high resolution data has also permitted the identification of habitat use of the Critically Endangered smalltooth sawfish (Pristis pectinata) (Guttridge et al., 2015). Here we have revealed diverse, fine-scale space-use by basking sharks, whereby collectively tracked sharks occupied the same area throughout the summer months, but movements within this area differed at an individual level, which is critical in understanding plasticity of space-use and habitat preference.

42. Residency and site fidelity

Residency, where an individual remains in a restricted geographic area for an extended period of time, and site fidelity, the return of an individual to a location where it previously resided after having left for a sustained period of time (Speed et al., 2011; Chapman et al., 2015) are common in shark species, with most data for reef associated species (see Chapman et al., 2015 for review). There is, however, a paucity of information on intra- and inter-annual shared use of an area by multiple basking sharks. Tracked sharks exhibited seasonal summer residency to the coastal waters off the west coast of Scotland. The vast majority of tracked sharks in this analysis (86%; n = 31) showed some degree of residency (> 50% locations) to the proposed MPA (Fig. 2). We reveal tracked sharks exhibiting inter-annual site fidelity returning to the coastal waters of West Scotland. Two individuals returned to waters encompassed by the proposed MPA in summer months in the year following tag attachment, returning to within 30 km of the centre of activity from the previous summer, with another shark returning to waters off the west coast of Scotland, 138 km from centre of activity from the previous summer in an area highlighted as having conditions suitable for basking sharks (Fig. 3; Paxton et al., 2014). Until the present study, attachment durations of tags to basking sharks have been insufficient to ascertain information on inter-seasonal migration routes; we present the first description of multiple individuals exhibiting residency and site fidelity in this species.

Space-use within proposed MPA boundaries. Shark locations within the proposed MPA boundaries per year, showing size and overlap of activity areas. MCP = Minimum Convex Polygon; MPA = Marine Protected Area; T-LoCoH - Time Local Convex Hull.

Geolocation method Number of sharks

Number of best daily filtered locations MCP area (km2)

Locations in MPA (median ± SD; (range); %) MCP area per shark (mean ± SD (range); km2) T-LoCoH isopleth area (50% hull (25-75%); km2) T-LoCoH isopleth overlap with MPA (50% hull (25-75%); %) Kernel area (50% contour (25-75%); km2) Kernel overlap with MPA (50% contour (25-75%); %)

Argos 8

235 21,182

80 ± 32 (20 -100) 2605 ± 3610 (477-11,123) 296(88-1372) 93 (100-73) 309 (97-728) 97 (100-87)

Argos 19 674 24,532

90 ± 14 (46-100) 3154 ± 2904 (250-10,470) 591 (190-2282) 90(96-94) 635 (181-1662)

100 (100-100)

194 9402

74 ± 26 (25-100) 3258 ± 2344 (552-5984) 221 (52-1106) 91 (100-68) 211(51-601) 90 (100-72)

Fig. 2. Identifying areas of relative importance. Areas of relative importance for the summer months (2012 to 2014; July-October) estimated using (A) Minimum Convex Polygon (MCP), (B) Grid density estimation, (C) Time-Local Convex Hull analysis (T-LoCoH) and (D) Kernel density interpolation with barriers. In 2012 and 2013 locations (white circles) are daily highest quality Argos locations from basking shark tagged with SPOT and SPLASH-F tags. In 2014, locations (white circles) are daily highest quality GPS locations from SPLASH-F tags. Proposed MPA (blue polygon).

Other tracking studies have indicated site fidelity and residency occurring in large, migratory sharks (e.g. white (Carcharodon charcharias), (Bonfil et al., 2005); whale, (Wilson et al., 2006); oceanic whitetip (Charcharhinus longimanus), (Howey-Jordan et al., 2013)), highlighting specific areas of use by these animals that would be suitable for protection (Kock et al., 2013; Howey-Jordan et al., 2013; Graham et al., 2016).

White sharks have been shown to exhibit a high degree of residency and site fidelity, returning to either the central Californian coast (Jorgensen et al., 2010) or Guadalupe Island (Domeier and Nasby-Lucas, 2008) after migrating to a shared offshore foraging area in the Pacific Ocean. There is potential for a similar pattern of seasonal movement occurring in basking sharks in the north-east Atlantic, whereby the coastal waters

off the west coast of Scotland serve as a shared, seasonal foraging site, with basking sharks moving away to separate over-wintering areas, as there is evidence for plasticity in dispersal behaviours during winter migrations (Doherty et al., 2017).

42.1. MPA use

Protection of highly migratory species throughout their range and life history is likely not feasible but MPAs can be used to protect areas of high relative importance or areas supporting key stages of life history ecology, such as breeding or foraging grounds (Lauck et al., 1998; Hooker and Gerber, 2004). Establishing management and protection measures for highly mobile species will likely rely on the premise that if protection of areas encompassing key life history events is achieved, populations may be better sustained (Speed et al., 2010). In a summary of evidence for the value of no-take zones for reef shark species, Escalle et al. (2015) found 65% of these studies deemed the protection area assessed to be beneficial to sharks, but 35% of studies suggested designated areas were too small based on residency, home-range and space-use; concluding that marine reserves have the potential to benefit sharks, but will be dependent on the amount of time individuals spend within reserve boundaries and the number of life-history stages catered for by the reserve.

Most protected areas are designated with their efficacy tested post-hoc, if at all, which may result in the assigned areas and boundaries being unsuitable. This can create a situation where adjustments in boundaries would be needed to provide protection of more appropriate areas, e.g. expansion of protective measures to include U.S territorial waters would effectively protect 100% of core activity areas of highly mobile sharks in the north-west Atlantic (Graham et al., 2016), or a buffer zone of an MPA acting as a year round exclusion zone to industrial trawlers would greatly increase protection of turtles in central Africa (Witt et al., 2008). If MPAs are designed with prior knowledge of space-use by species of conservation concern, and designated based on those findings, then they will more likely serve their purpose. In the present study, we have been able to robustly test basking shark space-use of a proposed MPA, prior to designation, in order to evaluate its potential spatial efficacy. We determined a mean of 84% of locations occurred within the boundaries of this proposed MPA across three years of study (Table 1). Core activity areas were robustly tested across multiple analytical techniques, all of which resulted in overlap of these core areas (>90%) with the proposed MPA (Fig. 2).

Basking sharks were observed foraging at the surface within the proposed MPA, however, there is potential for this area to provide suitable conditions for other life-history events. Nose-to-tail following and breaching behaviours were also observed in this area; behaviours that have previously been attributed to courtship (Harvey-Clark et al., 1999; Sims et al., 2000; Wilson, 2004), although mating has never been observed. Boat-based transects have also shown the area to have a high level of shark occurrence (mean 1.74 sharks hour-1), where large groups (> 10 individuals) can be seen aggregating, with individuals within these large groups displaying courtship-like behaviour (Speedie et al., 2009), supporting the notion that this area is a hotspot for basking sharks.

4.3. Application and MPA management recommendations

MPAs can only be effective if appropriate management and enforcement are employed to reduce threats to species for which they are designated. We have observed basking shark behaviours, often at the

Fig. 3. Inter-annual site fidelity. Best daily filtered locations (red and blue circles for 2013 and 2014 respectively) within summer months for three sharks demonstrating inter-annual site fidelity to coastal waters off the west coast of Scotland. Minimum Convex Polygons (red and blue polygons for 2013 and 2014 respectively), geographic mean centroid of Argos locations (red and blue crosses for 2013 and 2014 respectively). Shark ID and total tag attachment duration indicated for each figure part. Proposed MPA (grey polygon). 50 m bathymetry contour (grey broken line).

surface, occurring within the waters off the west coast of Scotland. The threats to this species are therefore likely to primarily occur from boat strikes (leisure and tourist boats, commercial transportation and fishing vessels) or fisheries activity (entanglement or by-catch). It is often argued that MPAs are too small, often containing a small proportion of a population at any one time (Wilson, 2016). However, after testing the space-use of basking sharks in the region, we reveal that high levels of core activity occurred within the boundaries of the MPA. Nevertheless, there is evidence for complementary MPAs to encompass other areas of use observed in satellite tracked basking sharks, most notably off the north-west coast of Ireland, the north coast of Northern Ireland and the waters to the west of the Outer Hebrides. We suggest that the areas of higher relative importance within the proposed MPA boundary should represent zones where vessel speeds are reduced, potentially seasonally between May and October (Speedie et al., 2009), fishing gear, in particular bottom set static gear (entanglement) or trawls (by-catch) are regulated and where leisure and tourist boats should adhere to the wildlife-watching best practise guidelines such as, Scottish Marine Wildlife Watching Code (SMWWC; and the Wise Scheme ( when sharing waters with marine wildlife.

5. Conclusion

Basking sharks are capable of extensive movement (Doherty et al., 2017; Gore et al., 2008; Skomal et al., 2009), and are an important species of conservation concern in UK coastal waters. Until now there has been a paucity of high-resolution, seasonal information on space-use in basking sharks. The present study provides near real-time tracking of multiple individuals at a shared foraging site in the coastal waters off the west coast of Scotland. We identify core activity areas occurring within the boundaries of the proposed MPA, providing an opportunity for specific management to be implemented within the area. Our work also highlights the repeated seasonal use and inter-annual site fidelity of this area, which may provide suitable conditions for other key life-history events as well as foraging. This study was able to substantiate the importance of the area and assess how basking sharks use the proposed MPA prior to designation, a process not usually afforded to most MPAs.


This project was funded by Scottish Natural Heritage and the University of Exeter. We extend our sincere thanks to the skippers and crew of the Sula Crion and Bold Ranger of Sealife Surveys, Tobermory. The attachment of satellite transmitters was regulated by the UK HM Government Home Office under the Animals (Scientific Procedures) Act 1986 (Project Licence 30/2975) and under the Wildlife & Countryside Act 1981 (as amended) (License(s): 13904,13937 and 13971). PD was supported by a NERC PhD studentship NEL\L501669\1.

Appendix A. Supplementary data

Supplementary data to this article can be found online at http://dx.


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