A Field Season of Basking Shark Research in the Sea of Hebrides 2019

This summer, a team from the University of Exeter have been on field work in the Inner Hebrides tracking and filming basking sharks! Read on to find out why…

Words by Owen Exeter, Christopher Kerry and Jessica Rudd.

Basking sharks are the world’s second largest fish and one of the UK’s most iconic marine species. Understanding the lives of these endangered fish is key to their conservation. Since 2012, researchers from the University of Exeter led by Dr Matthew Witt and Dr Lucy Hawkes in collaboration with Scottish Natural Heritage’s Dr Suzanne Henderson have been working in the Sea of Hebrides to understand how and why sharks use these coastal waters. This year the team are applying a variety of technologies to investigate the secret life of basking sharks below the surface.

Left: Dr Suzanne Henderson, Dr Lucy Hawkes and Dr Matthew Witt. Right: Image taken by REMUS.

Previously, most of our knowledge of basking shark spatial ecology and behaviour has relied on surface observations limited by daylight and weather conditions. With the recent advances of tracking technologies, we have gained unprecedented insight into their UK distribution, diving behaviour, long distance migration and inter-annual site fidelity. Satellite telemetry data acquired by the Exeter team have confirmed the waters off the Isles of Coll and Tiree as spatially important to the species (Doherty et al. 2017). These findings have directly informed conservation management with the proposed Sea of the Hebrides MPA currently under consultation.

Recently the team’s research has shifted to exploring whether the region has further significance to the species. Little is known about basking shark reproductive behaviour, fine-scale movement or habitat preference. 2017 saw the successful deployment of multichannel tags recording behaviour at the sub-second level (Rudd et al. in prep) and in 2018, custom made cameras designed by MR ROV started elucidating some of these questions. This year we were joined by a team from Woods Hole Oceanographic Institute (WHOI) and their Autonomous Underwater Vehicle (AUV) REMUS, with further towed cameras to deploy and a sonar scanner to attempt to shed further light on the rarely seen secret life of basking sharks.

Field site: Isles of Coll and Tiree, Inner Hebrides, Scotland.

Woods Hole Oceanographic Institute REMUS

REMUS is an AUV, a two-meter-long submersible vehicle that is designed to record underwater footage without manual controls from the surface. This allowed us to conduct long deployments at distances of over 2km from our control boat. Developed by Amy Kukuyla and her team at WHOI, REMUS has previously been deployed to film white sharks, bull sharks and leatherback turtles at depth.

As REMUS relies upon a tracking beacon tag being attached to the sharks half our team set off early from Tobermory harbour to locate and deploy tags aboard vessel Bold Ranger. The control team, including WHOI staff, followed on Etive Explorer. We successfully deployed beacons on multiple sharks across several days. Once tagged, we launched REMUS which followed the sharks at predetermined distances for up to four hours each mission. REMUS has 5 frontal cameras with an optional rear camera allowing near 360 views to be captured and up to 24 hours of footage generated per mission. Members of the team are currently stitching these different camera views together for each mission to allow further processing and analysis of the footage.

Left: REMUS. Right: MR ROV towed camera.

Towed camera deployment

Last summer, the towed cameras revealed new and exciting footage, including the very first shark aggregation observed on the seabed. While basking sharks may aggregate at the surface to feed, it remains unclear why they may do so at depth. Wanting to build upon these initial findings and hope to uncover more novel behaviour, this year we set out to re-deploy three cameras for a longer duration. These tags encase a temperature-depth recorder tracking the shark’s movement throughout the water column while filming it with a rear and front facing camera attached just below the dorsal fin by a 1.5 m tether. A vital component to the tag package is the Programmed Time Release which enables us to set the time at which we wish the camera to pop off the shark after a desired period and an integrated satellite tag, allowing us to track the camera remotely once its antennae breaks the surface by relaying its position every hour.

Footage acquired from 2018 MR ROV towed cameras.

This season the team was again successful in deploying all three camera tags. Upon release we deployed a range of tech to help us successfully hone into the position of the cameras. Once arrived at its last known coordinates, we used a goniometer which gave an idea of the bearing of the camera in relation to the boat. Within a certain range a handheld VHF radio (above the surface) as well as a VEMCO acoustic pinger (underwater) provide extra confidence in the directionality and distance to our prized tags.

While two of the sharks remained close to Coll, the third shark swum towards the Isle of Harris in the Outer Hebrides, nearly 150km north of it’s initial attachment. After a stroke of luck, a skipper and boat were found to help locate the last tag, known as Mr ROV Green, but required us to leave Mull, cross the mainland and drive across Skye before being picked up by a rib to find the camera. With the final mission successfully completed and all three camera tags found, now comes the exciting part of reviewing footage from both the cameras and REMUS to discover what new behaviours may have been recorded, along with answering biologically important questions such as estimating feeding rates and tail beat frequencies, as well as possible interactions with other basking sharks.

Finally, we would like to say a big thank you to Matt, Lucy and Suz for their knowledge and support during this field season. Interacting with a range of field technologies and seeing our data feed directly into policy and management is an invaluable experience for early career researchers. This work wouldn’t be possible without their hard work and dedication. We would also like to extend our thanks to Sky Ocean Rescue, WWF and Scottish Natural Heritage for their support of the project.

If you would like to updates on the basking shark project and our team’s other research please follow via twitter: Owen @OExeter,  Chris @chriskerry1989  and Jess @jlrudd.

The team. Clockwise from top left: Dr Lucy Hawkes, Dr Matt Witt, Owen Exeter, Chris Kerry and Jessica Rudd

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, biological,  medical, engineering, humanities and social science fields.

Find us on: Facebook : Twitter : Instagram : LinkedIn  

If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!

Shark Awareness Day: Plastic pollution – problematic for sharks and rays.

For Shark Awareness Day 2019 we have been chatting to a few of our elasmobranch (that’s sharks, skates and rays) researchers here the the University of Exeter! In this blog we talk to Kristian Parton one of our Masters by Research students based at our Penryn Campus. He has recently published his first research paper giving a global overview of shark and ray entanglement. Below he tells us about his research and what he has found.

Words by Kristian Parton, Masters by Research Student at the University of Exeter, Penryn Campus

Numerous shark populations around the world are under-threat from a variety human impacts, the most notable of these being overexploitation and bycatch. Plastic pollution and marine debris is also an ever-growing threat to species inhabiting the marine environment, having direct impacts on fish, sea turtles and marine mammals. There is little existing scientific knowledge on the impacts of marine debris on shark and ray species. Over the last year, I led a team of researchers from the University of Exeter seeking to investigate the impacts of anthropogenic (human-made) marine debris on elasmobranch populations across the globe. Our literature review was published this week in Endangered Species Research, in which we used novel data collection from social media site “Twitter”, as well as pre-existing data in the scientific literature. We discovered that the threat of marine debris to sharks and rays is likely underreported and is without doubt of clear animal welfare concern, although it is unlikely to have wide-ranging detrimental population level effects.

We managed to identify that “ghost fishing gear” was the category of marine debris responsible for entangling the majority of elasmobranchs. Ghost fishing gear is fishing equipment that has been discarded or lost at sea, and is distributed by ocean currents and winds. Ghost gear indiscriminately catches and kills a host of marine life, including sharks and rays.  We also discovered the majority of entangled individuals were found in the Atlantic and Pacific oceans, although recommend that more research should also be conducted in the Indian ocean – a known hotspot for elasmobranch biodiversity. In the scientific literature the most common entangled species were lesser spotted dogfish and spiny dogfish, two species regularly found off the coast of Cornwall. We highlight that sharks and rays who have specific habitat niches (e.g. those that inhabit the seafloor or species that occupy open ocean habitats), as well as those who display migratory movements may be at higher risk of entanglement in marine debris.

This Short-fin Mako Shark has been entangled in fishing rope which has caused scoliosis (deformation) of its spine. Image by Daniel Cartamil

By using a novel method of data collection via social media site “Twitter”, we were able to identify several different species of shark and ray that were a victim of entanglement, but weren’t found as entangled in the scientific literature. This included whale sharks, basking sharks and oceanic white-tip sharks. Twitter also highlighted additional entanglements hotspots that again weren’t displayed in the scientific literature.

Although not one of the major threats to sharks and rays, entanglement in marine debris still presents a risk to elasmobranchs, particularly from an animal welfare perspective. With further research on the topic, it could be revealed that this is occurring at far higher levels than we have reported. Social media has now become integrated into today’s society, so using it in a positive way to help reveal additional entanglement reports is a real bonus. With millions of users, the global reach of social media is unprecedented and scientists could now start to tap into the virtual databases that exist on the web.

From this research, we have set up an online entanglement report form in collaboration with the Shark Trust. This will allow citizen scientists across the globe to submit their shark and ray entanglement sightings, and will significantly help scientist further quantify this risk to ever declining elasmobranch populations.

Follow Kris on Twitter.

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, biological,  medical, engineering, humanities and social science fields.

Find us on: Facebook : Twitter : Instagram : LinkedIn  

If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!

Shark Awareness Day: Eye of the Tiger – Conducting Landing Surveys in Sri Lanka

For Shark Awareness Day 2019 we have been to talking to some of our elasmobranch (that’s sharks, skates and rays) researchers! Here, University of Exeter PhD student Claire Collins tells us about her research in Sri Lanka working to understand the shark fishery there so we can better manage them.

Tiger shark awaiting sale by shark traders in the early morning

Words by Claire Collins, University of Exeter PhD student.

I am 2nd year PhD student studying the socio-economic context of pelagic fisheries in Sri Lanka and India, specifically distant water vessels that target sharks (along with other large pelagics). As part of my research I will study the socio-economic value chains associated with sharks, the spatial movements of vessels and the perceptions of fishers with regards to national and international conservation regulations. To do this I will use a variety of methods including landing surveys, focus groups, household surveys and observational data. It is hoped that at the end of the project we can understand more about what motivates fishers to target sharks in distant water areas and how policy and management can be improved to benefit fishers’ livelihoods and shark populations.

Sharks are threatened globally by both targeted fisheries and through accidental capture in other large pelagic fisheries. Understanding the impact of anthropogenic activities is important and relies on accurate landings and discards data. However, for many fisheries globally the status of sharks as bycatch, and the difficulties in identifying them to a species-level means that we don’t have a clear idea of levels of fishing. The Indian Ocean has been identified as an area where populations of sharks are particularly poorly understood. As part of my PhD project I will be focusing on collecting data on landings and discards of sharks, as well as fishers perceptions of their livelihoods as shark fishers and how management and regulations effects them. One way to collect this data is through landing surveys in markets. These surveys are dual purpose for us, as we are able to collect landings data (including information on price and who is buying them) and we also get to speak to people whose job it is to understand shark movements and populations; the fishers!

Fishers with sharks caught incidentally during fishing for large pelagics such as Tuna and Billfish

Market surveys are not for the faint-hearted as they are frantic, start incredibly early (3AM at one of our sites) and the resulting smell means researchers are often unsuitable for travelling on public transport/sitting in cafes afterwards! Upon arriving at the markets researchers familiarise themselves with fishers and traders and look out for the first landings of the day. In order to understand value chains associated with sharks the team collect weight and price information for each species of shark landed that day, along with the details of which individuals are selling and buying them. Sales are conducted quickly and sharks often disappear seconds after being offloaded, therefore researchers need to be quick and rely on their good relationships with traders and buyers. Within Sri Lanka shark fisheries are considered zero wastage, therefore the team has to collect price and weight data for the sales of meat, fins, liver, teeth/jaws and skin as well as whole sharks.

Meat and fins are separated for sale on the market side.

Our research team also conduct questionnaires with fishers that are landing to the markets on the subject of their fishing behaviours, attitudes towards sharks and the economics of their recent trip. These surveys are conducted by researchers with the captains of the vessels, often in the wheel-house, and tablets are used to help speed up recording and analysis. By combining data from both types of surveys, as well as interviews with other individuals such as shark traders, we can map out socio-economic reliance on shark resources. This will help us to understand likely impacts of changes in management and policy interventions on a national and international level. It could also offer policy-makers an insight into how fishers see their industry and livelihoods and what is important to them for the future.

Fishers are regularly gone for trips of over 2 months

All images taken by the author. This work is supported by the Bertarelli Foundation as part of the Bertarelli Programme in Marine Science and is conducted in partnership with the Zoological Society of London.

You can follow Claire on Twitter.

 

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, biological,  medical, engineering, humanities and social science fields.

Find us on: Facebook : Twitter : Instagram : LinkedIn  

If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!