Nurse shark and bait cannister

Research Insights: Kristian Parton – ‘Opportunistic camera surveys provide insight into discreet foraging behaviours in nurse sharks’

University of Exeter research associate Kristian Parton recently published a paper investigating the variety of foraging behaviours exhibited by nurse sharks in The Turks and Caicos Islands. Read on as we hear from him about this exciting research:

Kristian Parton – Research Associate, University of Exeter


Hi Kristian, thank you for joining me. Why don’t we start with a little about yourself and your work?

Hi, my name is Kristian, and I am a research associate at the University of Exeter. I studied my undergraduate degree here back in 2014 in Zoology and then went on to study my Masters by Research, looking at the impact of plastic pollution on sharks. Since then, I’ve been doing bits of research on sharks with various companies, which leads on to this current research with a company called Beneath the Waves, a shark NGO over in the United States.

Brilliant. So tell us, what led to your new paper “Opportunistic camera surveys provide insight into discrete foraging behaviours in nurse sharks (Ginglymostoma cirratum).”?

Over the lockdown in 2020, whilst like most of us I couldn’t get out anywhere, Beneath the Waves were in the Turks and Caicos Islands dropping baited remote underwater video systems in an attempt to look at the biodiversity of sharks around the islands. There’s not that much research that’s been done in the Turks and Caicos on sharks and rays, so Beneath the Waves were using these BRUVS to see what species were out there. For those of you who are new to BRUVS, they stand for Baited Remote Underwater Video Systems, and essentially, they are rigs which are dropped to the seafloor with a camera attached, plus a pole with a bait cannister on it. That bait will then lure in any marine predators like sharks and rays, which are viewed on the camera. Usually, they are used to study abundance and distribution of different species in an area.

As part of my work for Beneath the Waves, I was analysing the BRUVS footage. This involved going through and identifying the various shark and ray species which were coming onto the cameras. As I was looking through the footage, I started to notice the nurse sharks were doing something slightly strange and were behaving differently around the bait cannister to the other sharks that were featuring on the BRUVS, like the Caribbean reef sharks.

Whilst most of the other shark species would just hit the bait cage quite hard and pull it around, the nurse sharks would spend far longer, approaching the bait from different angles and positions. I started posing a few questions and went back to the team at Beneath the Waves. They’d also seen a clip of a nurse shark that looked like it was using its pectoral fins, bending them and arching them, to almost ‘walk’ on the seafloor around this BRUV. So, I started looking at more of the videos back-to-back, and we saw some patterns developing. These nurse sharks were all doing similar behaviours on the BRUVs. And so this paper was an attempt to classify those different behaviours.

Nurse shark and bait cannister

Nurse shark (Ginglymostoma cirratum) interacting with bait cannister


And what did you go on to find?

We found that nurse sharks have a variety of different foraging behaviours they can use. We went through and classified four foraging behaviours and one non-foraging behaviour. The first behaviour is vertical feeding, where the shark has positioned its body above the bait cage, with their head down and a vertical posture in the water. Then we’ve got the pectoral positioning behaviour, which we said looked like walking, where the sharks are arching and bending one or both of their pectoral fins, touching them against the sea floor and then using them to propel and move themselves around the bait. Then we’ve got the stationary horizontal feeding behaviour, so this is where a shark is horizontally positioned with its head close to the bait cage. It can be performed at different angles but generally the shark is flat, lying motionless on the seafloor and just sucking at the bait cage. Then we’ve got the ventral feed, where the shark is almost flipped upside down onto it’s back, with its belly facing upwards towards the surface and is trying to get underneath the bait cage. The final behaviour is the swim pass with the shark just swimming past the BRUV and not interacting with the bait cage.

BRUV footage of nurse shark foraging behaviours.


So, after classifying those different behaviours, we wanted to see what the purpose of these behaviours was and if there were any trends. Was depth affecting those behaviours? Was habitat type affecting those behaviours? We found that depth did affect one of the behaviours, which was the swim pass behaviour. In deeper water the sharks were swimming past less than they were in shallower water. This is potentially because nurse sharks could be feeding at deeper depths. However, this was not directly related to the foraging behaviours. We also wanted to compare the different foraging behaviours and whether they differed in sandy bank habitats, compared to reef habitats. Putting all the stats together we did find that the stationary horizontal feeding behaviour was more common on the bank habitats, the behaviour where they’re lying almost motionless on the seafloor. That’s probably because that behaviour is an easy behaviour to perform, it doesn’t require a lot of energy. They can simply lie there on a sandy bank habitat because there’s nothing obstructing them like there would be on a reef habitat, where corals might be getting in the way.

We didn’t find any trends between the other foraging behaviours based on habitat type, but we do think, even though we couldn’t prove it with the stats, that those more complex behaviours, like the vertical feed, are probably more common on the reef habitats. They could be used by the nurse shark to traverse their way around rocks and corals, and that might make it easier for them to get to that bait.

We also looked at the pectoral positioning behaviour, which we loosely termed as ‘walking’, although that’s a very human way of looking at it. We had another scientist come on board who knows a lot about the inner muscle workings of nurse shark pectoral fins. Unlike many other shark species, nurse sharks have specific skeletal and muscular adaptations of their pectoral fins that allow them to bend them in that way. This is similarly seen in the epaulette shark, a relative of the nurse shark, which we know is a species which can truly walk across rocks using its pectoral fins. We think that potentially nurse sharks and epaulette sharks have similar adaptations in their pectoral fins that allow them to exhibit this behaviour.

And so why is this research important?

When we look at this in real world terms, if we remove the bait, in a complex reef habitat a nurse shark might be trying to get to prey that could be hiding under rocks and corals. The range of different foraging behaviours they can use helps them capture that prey when they might be in tricky habitats. They can use the different behaviours in their repertoire.

This research therefore illustrates the behavioural adaptability of nurse sharks across a variety of habitats and provides further understanding of their ecological role, as we know quite little about them.

Summary of Kristian’s paper: Opportunistic camera surveys provide insight into discrete foraging behaviours in nurse sharks (Ginglymostoma cirratum).


Have BRUVS been used to look at behaviours like this before?

BRUVS really haven’t been used to analyse behaviour that much in the way that we’ve used it in this paper. It has been done in the literature but its not the normal way that scientists use BRUVS. Generally, they’re used to look at relative abundance and species diversity across space and time and so this was an interesting way to look at behaviour.

Obviously, there are limitations to using BRUVS in this way. We have to think about the fact that we are using bait, a simulated food offering, to attract sharks and observe their behaviour. The behaviours we observe are influenced by the fact that we’ve lured the sharks in. We posed however that the alternative is too difficult. The number of hours in the water it would take for people to observe these behaviours naturally, we just wouldn’t collect enough data. We also have to consider other challenges, for example not being able to differentiate between individuals on the BRUVS. So, it could be only one or two sharks that are performing these behaviours. We did counter for that by spacing these BRUVS around the islands, in many different areas, so we would obviously hope its not just one shark moving from one to the next. But overall, it was a really interesting piece of work and it was great to work with Beneath the Waves on this, alongside scientists at the University of Exeter.

Check out Kristian’s Youtube Channel “Shark Bytes” below: CRAZY Nurse Shark Feeding Behaviours (My Research!) – YouTube

Follow this link to read the full paper: Opportunistic camera surveys provide insight into discrete foraging behaviours in nurse sharks (Ginglymostoma cirratum) | SpringerLink

Research Insights: Dr Phil Doherty on “SharkGuard” – A Novel Bycatch Mitigation Device

Oceanic sharks & ray populations have declined >70% in the last 50 yrs. ExeterMarine lecturer Dr Phil Doherty recently published an exciting paper using a novel device, “SharkGuard”, which uses electric pulses to deter sharks from fishing hooks in an effort to reduce bycatch. This may provide hope for the future of sharks and rays – read on as we chat with him about this work.

Dr Phil Doherty, Lecturer in Marine Conservation Science, University of Exeter


Hi Phil, thank you for joining us. To start with, can you give us a bit of background about yourself and your research?

Hi, thanks for inviting me – my research largely focuses on the presence and movement of large vertebrates, particularly sharks. For example, my PhD focused on tracking basking sharks in UK waters. I tend to use different technologies and methods to try and look at where things are, when they’re there, and what they might be doing there. I also try to inform on implementing some sort of management or policy strategy to try and make sure that times when these species of conservation concern are vulnerable, or are in places in high numbers, that they have some level of protection, whether that’s an MPA or another form of mitigation.

This has developed more recently into using fisheries data to look into catch composition and seasonality of fisheries landings to try to look at ways to prevent certain species being caught, certain sizes being caught, and more recently looking at bycatch (unwanted or unintentionally caught species) specifically. We are trying to get a grip on species that are being caught when they shouldn’t be, or aren’t wanted, and what we can do about that. Are there ways that we can prevent things being caught in the first place?

Bluefin tuna (Thunnus thynnus) catch onboard a longline vessel in southern France.

Photo Credit: Fishtek Marine.


Focusing on shark bycatch, which is the subject of your recent paper, what is the issue there?

Sharks and rays are groups of species that span most trophic levels, provide many ecosystem services, and are found in every ocean; so, talking about sharks and rays in general is quite difficult. However, in terms of larger bodied sharks and rays, and especially oceanic and pelagic species, their populations are under massive strain and most of that is from fishing pressure. Some of this is intentional capture, where sharks and rays are caught as the target species, but more often sharks and rays are caught as bycatch, as these species are often found in similar areas, exploiting similar resources as the target species.

This is having a massive impact on populations and these oceanic species that show more broad-ranging movements get caught a lot, due to high overlap with the big fisheries – the big purse seine and longline fisheries. This can cause a problematic scenario, which is often is a two-way thing, the fisheries quite often don’t want the sharks and obviously the sharks don’t want to be caught, but the numbers currently caught is really detrimental.

And so, what research have you been undertaking recently?

We have been working with Fishtek Marine, a conservation engineering company based in Devon. They develop all sorts of devices and mitigation strategies to try and prevent lots of different bycatch, from seabirds to turtles to cetaceans; and now for sharks and rays. They’ve developed a device called SharkGuard, which is a small device that you can fix just above a fishing hook on a longline, and it emits a pulsed electrical field around the baited hook.

Sharks and rays possess an extra sensory capability that bony fish and mammals largely lack. Sharks and rays have organs called ampullae of Lorenzini that are made up of small pores around their nose and mouth that can detect faint electrical impulses. It’s often how sharks and rays find prey, whether they’re buried in the sand or moving at the surface. The aim of SharkGuard is to overstimulate these electrosensory organs to deter the sharks and rays from engaging with the hook. It is quite effective in the sense that it’s a very short-range pulse, localised around the hook. Sharks have what’s known as a hierarchy of senses; switching between senses as they approach their prey ending with electrosensory capabilities very late on, just before biting the bait, only centimetres from their prey. Therefore, we have this short pulse, where we’re hoping that the shark might come close to the hook, but it won’t actually attempt to take the bait and therefore will swim away unharmed.

We trialled SharkGuard in a longline bluefin tuna (Thunnus thynnus) fishery in southern France, where they target bluefin tuna, a very prized resource, but the fishery is has a large bycatch component comprised mostly of blue sharks (Prionace glauca) and pelagic stingrays (Pteroplatytrygon violacea).

Schematic diagram depicting the effect of the SharkGuard electrical pulse.

Photo Credit: Fishtek Marine.


And you’ve had some very exciting results?

Yes, we tried this out with an experimental design where we aimed to have fishing operations exactly as it would be normally for the fishers. We alternated a control hook (normal fishing set-up) with a SharkGuard device attached to it. So, we had normal hook, SharkGuard hook, normal hook going all the way out. Two boats set longlines of 1000 hooks, 500 of each hook type, and they fished all summer like they would normally. We compared the catch rates for blue sharks, pelagic stingrays, and the target species, bluefin tuna to see if there was any difference between the hook types.

We found that the SharkGuard hooks significantly decreased the catch of both blue sharks and pelagic stingrays by huge amounts – a 91% reduction for blue sharks and a 71% reduction for pelagic stingrays.

Whilst we’re not trying to claim that we’ve solved bycatch for sharks and rays, this is a really important step to showing that this kind of device is effective for this sort of scenario. We’re now trying to look at other opportunities to try it in different fisheries to see how well it works, or how we might tweak the design to make sure that it can work for different species and in different environments.

We also want to make sure it is suitable for different target catch, because obviously fisheries aren’t going to uptake this kind of device if they don’t catch the things they do want to catch. So, it’s finding that balance, but we’re really impressed with the first trial results as we know it does work, it can work, and it’s important to try and start reducing this kind of bycatch.

SharkGuard devices attached to longline hooks in setting bins ready for deployment.

Photo Credit: Fishtek Marine.


Have there been any other kind of mitigation efforts like this before for shark bycatch?

Not quite like this. Researchers have tried all sorts of stuff, lights on hooks, sound, different smells to try and deter sharks, fishing at different depths, different times of the day – lots, and lots of different approaches. There was quite a push a while ago of trialling rare-Earth metals and magnets to try and almost create the same kind of effect that we were just talking about with a magnetic field. However, these effects don’t last very long in saltwater, so can be quite laborious as you have to change them quite often and their effectiveness reduces over time. The electrical deterrent side of things has focused more on development for personal use, so for people surfing or out on kayaks with wristband type designs, having mixed results. The development from this side of things is quite novel in terms of putting electronic devices on the hook. The technology and the idea have been around for a while, but this kind of application is new.

Do you think that the devices will be well accepted by fisheries?

Yes, I really hope so – we’ve had some pretty positive feedback so far. I think it’s because we’re not trying to tell people to not fish, we’re trying to just say if you fish, can you maybe put these devices out and maybe give the sharks and rays a chance. The fishers that we worked with in France liked it because it didn’t change how they set up their gear or approached fishing activities. They still had their same way of putting the hooks on the line and bringing the catch back to the boat. It didn’t get in their way, and it wasn’t extra work.

Normally, when they do have bycatch, they just cut the line, so, potentially the shark or ray is cut loose with a hook in its mouth and trailing fishing line with the thought that it swims away and survives, but this may not be the case. The fishers then have to spend time fixing the line and attaching replacement gear. Also, catching a stingray that’s not very happy or a shark is dangerous for the fishers and as such don’t want them on the line. Plus, any hook that doesn’t have a shark on it could have a tuna on it instead, so the benefit could be huge.

Fishtek are in the process of developing induction charging bins, so when the hooks are placed back in the bins after hauling a set, it automatically charges the SharkGuard devices reducing effort for the fishers and removing need to replace batteries. We’re trying to make it as bulletproof as possible. Yes, there’s a large financial outlay in the beginning, but once setup you’re good to go.

Take a look at the video below to see the story so far…

SharkGuard (the story so far…) – YouTube

Read the full paper: PD Doherty, R Enever, LCM Omeyer, L Tivenan, G Course, G Pasco, D Thomas, B Sullivan, B Kibel, P Kibel, BJ Godley (2022). Efficacy of a novel shark bycatch mitigation device in a tuna longline fishery. Current Biology:

Exeter Marine Podcast – Arctic Terns, Basking Sharks; Bluefin Tuna, with Dr. Lucy Hawkes


In this episode we talk to Dr. Lucy Hawkes about a number of her research areas including arctic terns, basking sharks and bluefin tuna. Listen out for a story about a mysterious tuna tag as well.



About our guest: Dr. Lucy Hawkes 

Lucy is a physiological ecologist, whose work focuses on the costs and drivers of migration in animals (vertebrates and invertebrates) using emergent technologists such as satellite telemetry, heart rate logging, accelerometry and metabolic rate measurements. Lucy uses technical approaches including biologging, spatial ecology, remote sensing and respirometry to make empirical measurements that help in the understanding of amazing migratory performances. Lucy’s work has also investigated the impact of external forcing factors, such as climate change and disease ecology on migration and breeding ecology.


Above: Dr. Lucy Hawkes, Dr. Matt Witt and the team working with basking sharks. Photo credits: Nic Davies



Topics discussed:

  • Lucy’s experience as a National Geographic Explorer.
  • Tagging and studying bluefin tuna.
  • The long distance migrations of arctic terns.
  • Studying basking shark behaviour.
  • Breaching basking sharks.
  • The journey of a mysterious tuna tag (pictured right).






Basking shark videos






Episode and show notes produced by Ben Toulson and Katie Finnimore.

Check out other episodes of the podcast here.

You can subscribe on most podcast apps, if you’re feeling kind please leave us a review!

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Emily Easman or visit our website!



Exeter Marine Podcast – Coral Reef Bioacoustics Part I, with Prof. Steve Simpson


Show notes

In this episode Professor Steve Simpson talks to us about his research covering a number of topics focusing primarily on his bioacoustics work on coral reefs. He also discusses his work on Blue Planet 2 and recalls an encounter with David Attenborough.



About our guest: Steve Simpson

Professor Steve Simpson is a marine biologist and fish ecologist. His research focuses on the behaviour of coral reef fishes, bioacoustics, the effects of climate change on marine ecosystems, fisheries, conservation and management. Following a NERC Knowledge Exchange Fellowship Steve has ongoing links with industry and policy on the themes of European Fisheries and Climate Change, and Anthropogenic Noise and Marine Ecosystems. Steve works closely with Cefas and the Met Office, and is an active member of the IQOE Science Committee, he has been an Academic Advisor and featured scientist in Blue Planet 2

Steve’s work combines fieldwork, often through expeditions to remote and challenging environments around the world, with laboratory-based behaviour experiments, data-mining, and computer modelling.

Steve’s research focuses on:

  • The impact of anthropogenic noise on marine ecosystems.
  • The effects of climate change on fish and fisheries.
  • Sensory and orientation behaviour of marine organisms.
  • Dispersal, connectivity and biogeography.
  • Coral reef restoration.
  • Fisheries and Conservation Management.




Topics discussed:

  • Bioacoustics of coral reefs.
  • How underwater sound can reveal animals we rarely observe visually on coral reefs.
  • How fish choose communities to live in by listening.
  • Is the underwater world silent?
  • How do underwater species hear?
  • How do you record an underwater soundscape?
  • Blue Planet 2 and David Attenborough.



TEDx 2019 Talk: Changing the Soundtrack of the Ocean

BBC Earth Film: Underwater acoustics work

Agile Rabbit Talk: Underwater Sound in Blue Planet II

Facebook Live: Q&A Session

Article: Exeter marine expert awarded prestigious medal for scientific contribution




Episode and show notes produced by Ben Toulson and Katie Finnimore.

Check out other episodes of the podcast here.

You can subscribe on most podcast apps, if you’re feeling kind please leave us a review!

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Emily Easman or visit our website!


MSc Graduate In Focus: Catherine Hart

This year we are launching a new MSc in Marine Vertebrate Ecology and Conservation and applications are open now for 2020 start. We are looking back on some of our MSc graduates who have excelled in marine vertebrate ecology and conservation around the world since studying with us.

Today we meet Catherine Hart, MSc Conservation and Biodiversity graduate (2009) and now scientific director for the Red Tortguera (Sea Turtle Network) in Mexico!

Hi Catherine! First off, why don’t you tell us what you are up to now and how you got there?

I moved to Mexico when I was 19 after having been a volunteer on a sea turtle conservation project in Nayarit state and then undertaking an undergraduate degree there. It had always been my intention to go straight back after the master’s course. On arriving back, I began to run the field conservation work for a small NGO and then when it was low sea turtle season taught secondary school science and did a little gardening/child minding on the side. In 2010 I decided that a PhD would be beneficial and allow me to continue my sea turtle conservation and research activities. The PhD was with the Universidad de Guadalajara in Puerto Vallarta and was supported through a scholarship from the Mexican government. During that period, I increased the number of nesting beach conservation projects that I was managing from one to seven and co-founded an NGO “Red Tortuguera” (sea turtle network). After the PhD I was accepted into the Mexican Researchers System (Sistema Nacional de Investigadores) which allows me to continue my research while conducting sea turtle conservation activities.

What did you enjoy most about studying your MSc with us at the University of Exeter Cornwall Campus?

I loved being by the sea. I am from Northampton so that’s about as far from the ocean as you can get in the UK. I loved how dynamic the UK tides are and I even loved the seagulls (which are not that popular).

Everyone on the course were amazing and had all done different conservation and research activities either during their undergraduate degrees or as volunteers. It was a great opportunity to learn about different places and conservation issues. The researchers at the Centre for Ecology and Conservation are world class and very approachable. I always felt that I could ask questions and didn’t have to be embarrassed for having no idea about some things that others knew from their undergraduate degrees in the UK.

What skills and experiences from the MSc have been most useful in your career?

I would say everything I learnt at Exeter has been useful. Firstly, having studied at a university known for its research on sea turtles has opened many doors not to mention that my masters project was on Mexican sea turtles and I was put in contact with some of the top researchers worldwide for East Pacific green sea turtles who I may not have gotten to know so early in my career if it hadn’t been for the introductions made by the Exeter researchers. This is something I am very grateful for as not only has it been great for my research and conservation activities but also for the friendships I have made. On a more academic note the courses on statistics and mapping software have come in very useful! Perhaps the most important thing that I learnt at Exeter is to have the confidence in myself and the experience that I had gained from years of fieldwork in Mexico.

Finally, why did you choose your career path and do you have any advice for those looking to pursue something similar?

It’s great to be able to help study and protect sea turtles and other local wildlife where I live. I like to think that I am making a difference. I have been in the same place long enough to see some of the results of our conservation activities and that is very rewarding.

Never turn down an opportunity to tag along on research trips, learn a second language and perhaps take a course in marketing.

Any advice for anyone thinking of applying to the University of Exeter?

Just do it.

Thanks Catherine!!

If you want to find out more about any of our suite of #ExeterMarine Masters and Undergraduate courses use the links below!

MSc Graduate In Focus: Joana Hanock

This year we are launching a new MSc in Marine Vertebrate Ecology and Conservation and applications are open now for 2020 start. We are looking back on some of our MSc graduates who have excelled in marine vertebrate ecology and conservation around the world since studying with us.

Today we meet Joana Hancock, MSc Conservation and Biodiversity graduate (2011) and now working with the Olive Ridley Project as a Sea Turtle Biologist!



Hi Joana! First off, why don’t you tell us what you are up to now and how you got there?

Having graduated from an MSc in Conservation and Biodiversity in 2011 well into my career as sea turtle biologist, I decided to slowly move away from previous jobs where I coordinated sea turtle nesting programs, to study and understand other less studied life-stages such as juveniles and males, and their role in sea turtle conservation. For this reason, I initiated my PhD studies in 2014 focusing on sea turtle foraging ecology, genetics and mixed modelling to understand how these life stages link to each other and how we could integrate them in conservation plans. Following on this specific research interest (foraging ecology and genetic connectivity) I am now trying to initiate a research program on Kenya’s south coast coupling sea turtle photo-ID mark-capture-recapture study, habitat mapping and population analyses, focusing on juvenile green turtles in foraging areas.

What did you enjoy most about studying your MSc with us at the University of Exeter Cornwall Campus?

The opportunity to study alongside with students from all areas of conservation and different parts of the world. Lectures from people working in different fields of conservation biology and student seminars provided valuable learning and eye-opening opportunities that were as valuable as the MSc program’s modules.

I really enjoyed the teaching system, it is very relaxed, in such way that it was very easy to interact and learn from the experienced lecturers and their support staff, who were always available and very supportive. The location is great, it is a very special campus and lab equipment as well as lecture theatres are top!

What skills and experiences from the MSc have been most useful in your career?

During the program we learn not only about topics in conservation, but also there are specific modules that teach you how to actually survive in the conservation world: from writing grant proposals, giving oral presentations, writing research papers, attending and preparing job interviews, etc. Extremely important!

Finally, why did you choose your career path and do you have any advice for those looking to pursue something similar?

I choose sea turtle biology and conservation nearly 20 years ago, and there was no turning back. Every day I learn from my interaction with turtles, with people who work with them, and mostly people who live of them. I could not imagine many more careers that can be so inter-disciplinary as working with marine vertebrates such as sea turtles. It can be hard at times, but most of the time it is a pleasure as sea turtle research progresses, turtles become even more fascinating. It is a humbling experience and always extremely rewarding!

This is a career to make your life richer, not necessarily your wallet 😉 With this in mind, keep your expectations low, accept all learning opportunities, but don’t get unmotivated. As you gain more experience things will start falling into place, and it will be a life-changing decision you will never regret!

Any advice for anyone thinking of applying to the University of Exeter?

Go for it, it is worth it!

Thanks Joana!

If you want to find out more about any of our suite of #ExeterMarine Masters and Undergraduate courses use the links below!

IPCC Research Confidence in the field of Coral Reef Futures – Jennifer McWhorter

Research Confidence in the field of Coral Reef Futures

(Based on IPCC 2019 Report, Chapter 5, Changing Ocean, Marine Ecosystems, and Dependent Communities)

Author, Jennifer McWhorter, PhD Candidate QUEX (Universities of Queensland and Exeter)

The Intergovernmental Panel on Climate Change (IPCC) consists of a team of top researchers and scientists advising global climate action. Recently, the IPCC wrote a special report updating research findings pertaining to 1.5 ℃ of warming, of particular interest to my field of research is the section on coral reefs. Based on Chapter 5 of the latest IPCC report (Bindoff, N.L et al., 2019), I have highlighted the consensus of scientific research by summarizing key topics of coral reef research by research confidence. In italics are statements summarized from the report.


Very High Confidence Overview of Research

Some alarming numbers on the future of coral reefs were confidently stated in the latest IPCC report, “coral reefs are projected to decline by a further 70-90% at 1.5 ℃ with larger losses (>99%) at 2 ℃ ”. Since the industrial revolution in the 19th century, human activities have contributed to approximately 1.0 ℃ of global warming. At our current rate of emissions, global warming is estimated to reach 1.5 ℃ between 2030 and 2052. (IPCC, 2019: Summary for Policymakers). To give you some perspective on those numbers, future generations will have a difficult time finding coral reefs in the state in which we have had the privilege of experiencing them.

The corals in the image above were photographed two months apart showing the effect of the last warming event at Pixie Reef, just north of Cairns, on the Great Barrier Reef. On the left, the corals are healthy and then two months later, the image on the right shows many of the same corals are stressed and near mortality (bleached or white in colour). (Photo credit: Brett Monroe Garner)


High Confidence Overview of Research

When the human body has a weakened immune system, such as experiencing chemotherapy from cancer treatment, a common cold or flu can be detrimental, leading to a worsened state or even death. Coral reefs facing multiple disturbances such as warming and ocean acidification, reef dissolution and bioerosion, enhanced storm intensity, enhanced turbidity, and/or enhanced run-off have a lower chance of recovery. In the future, when faced with multiple threats, there will be a shift in species composition and biodiversity. This shift will be towards soft corals and algal dominated reefs as opposed to reef building corals. Albeit, regional differences in levels of reef vulnerability exist on a scale of 100 km or by latitudinal gradients.

The image above portrays an example of the shift in dominance from reef building corals to a dominance of non-coral organisms, such as the pictured ascidian, Didemnum molle and algae in Palau, Micronesia. (Photo credit: Dr. Kennedy Wolfe)


Medium Confidence Overview of Research

Record breaking warm water temperatures during 2014-2017 resulted in severe and wide-spread global coral mortality (Eakin et al., 2019). The reefs that have survived this event have a higher thermal threshold resulting in a dominance of species that are not as sensitive and have a high adaptive capacity. Is this a glimmer of hope? Perhaps but, it is important to note that this is the category of medium confidence of an overview of the research.

Branching corals are typically less resilient in warm water conditions than stony, non-branching corals (Hughes et al., 2018). This juvenile Acropora (branching coral) offers hope of recovery on a reef in Palau, Micronesia. (Photo credit: Dr. Kennedy Wolfe)

In a physical world, the ocean is complex, different zones of the ocean experience various conditions in space and time. Coral reef habitats are not uniform. Deeper coral reefs (30-150m) and upwelling zones may serve as a refuge and source of larval supply to disturbed reefs. On the contrary, these reefs could be more at risk than suggested.

Low Confidence Overview of Research

Coral reefs require certain light and temperature conditions in order to grow. The rate of sea level rise may outpace coral growth. Sea level rise would send corals into deeper habitats potentially limiting these ideal light and temperature conditions.

Resilience and adaptation is broadly still unknown, few reefs are showing resilience. Luckily, some of the best in the world are working hard to close this gap.

In Palau, Micronesia, Professor Peter Mumby descends onto the reef. Pete’s Marine Spatial Ecology Lab conducts research into coral reef ecosystems, fisheries, modeling, and socioeconomics. (Photo credit: Dr. Kennedy Wolfe)

Support climate change research initially by learning about it. Thank you for reading.

You can follow Jen on Twitter to keep up to date with her research!

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

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



Bindoff, N.L., W.W.L. Cheung, J.G. Kairo, J. Arístegui, V.A. Guinder, R. Hallberg, N. Hilmi, N. Jiao, M.S. Karim, L. Levin, S. O’Donoghue, S.R. Purca Cuicapusa, B. Rinkevich, T. Suga, A. Tagliabue, and P. Williamson, 2019: Changing Ocean, Marine Ecosystems, and Dependent Communities. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.

Eakin, C. Mark, Hugh PA Sweatman, and Russel E. Brainard. “The 2014–2017 global-scale coral bleaching event: insights and impacts.” Coral Reefs 38.4 (2019): 539-545.

Hughes, T. P., Kerry, J. T., Baird, A. H., Connolly, S. R., Dietzel, A., Eakin, C. M., … & McWilliam, M. J. (2018). Global warming transforms coral reef assemblages. Nature, 556(7702), 492.

IPCC, 2019: Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.

Scientists at Sea Podcast – The Stingray Episode: with Ethan Wrigglesworth and Molly Meadows

In this episode, we get to know our regular presenters a little better. Ethan and Molly talk to Ben, the producer, about the work they have been doing as Masters by Research students for the past two years. Under the supervision of Dr. Lucy Hawkes, Molly and Ethan have been working closely with Dr. Owen O’Shea at the Cape Eleuthera Insitute (CEI) in the Bahamas, to study the stingrays in the local waters.



Molly and Ethan worked with two data deficient species of stingray; the Southern Stingray, and the Caribbean Whiptail Ray  The main focus of the research was to investigate the rays’ diets. This involved two methods; stable isotopes analysis and stomach content analysis (you can learn more about them in the podcast).


Ray team just after having caught a southern stingray along a sandbar. (Ethan first on left, Molly, second from right).


Why does this matter?

Well, as Molly and Ethan put it:

Molly holding the tail of a Caribbean whiptail ray presenting the large venomous barb.




“To understand about the diet is actually to understand general ecology… within an ecosystem, what a predator feeds upon… has a great impact on the population sizes of the prey, and there’s a huge amount of energy moving up in that food chain”







How might such research be applied? Well, in the Bahamas there is no legislation for the protection of mangroves.


“In the Bahamas, there’s lots of these mangrove creeks, and plenty of fish use them as nursery habitats because they offer a lot of shelter within the roots… stingrays occupy these systems as well… they feed on worms, crabs and things within the sea floor, so they use the mangroves a lot to find (their) food.”


You can find out more about why mangroves are so important here.


“Beaches are very popular in terms of tourist economy, so (mangroves) get destroyed quite a lot”


While the stingrays rely on the mangroves for food, it seems they also offer plenty to the mangroves themselves. To find out exactly what they offer, take a listen to the episode.


A free diver going face to face with a large Caribbean Whiptail Ray




You can also find out about some skills you might not know existed, like stingray herding!









Highschool/Island school student Jake holding a southern stingray during sampling procedures


Getting Started with Marine Science

Molly and Ethan initially honed their marine biology skills and interests as undergraduates here at the University of Exeter’s Penryn Campus, studying Zoology and Conservation Biology and Ecology respectively. In their final year they undertook a field course to Eleuthera Island in the Bahamas, this sewed the seeds of their Masters by Research. Click the links to find out more.



Here is a bonus link mentioned during the episode, enjoy! Household items reviewed for science


Videos courtesy of CEIBahamas

Hosted by Ethan Wrigglesworth and Molly Meadows

Episode and show notes produced by Ben Toulson

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!


It’s Stressful Being a Coral! Declining Coral Cover on the Great Barrier Reef

Author: Jennifer McWhorter

Jennifer McWhorter is pursuing her PhD in a joint program between the Universities of Exeter and Queensland. Using various climate and ecological modelling techniques, Jen hopes to improve our spatial knowledge of coral reef stressors.


The above diagram describes the process of coral bleaching followed by mortality. Source: Great Barrier Reef Marine Park Authority (GBRMPA)


Similar to humans experiencing a fever, coral reefs undergo similar stress. The more frequent the fever and the longer the fever lasts, the more life threatening it becomes. Sea surface temperatures in the ocean are increasing at an alarming rate due to human inputs of carbon dioxide into the atmosphere (Ekwurzel et al., 2017). In 2016/2017, the Great Barrier Reef (GBR) experienced two back-to-back severe warming events that caused widespread coral bleaching[1]. According to the Australia Institute of Marine Science, hard coral cover on the GBR has declined at a rate that has never been recorded.


Figure 2. “Large-scale spatial patterns in change in coral cover and in heat exposure on the Great Barrier Reef, Australia. A, Change in coral cover between March and November 2016. b, Heat exposure, measured in DHW (in degree C-weeks) in the summer of 2016. Map template is provided by Geoscience Australia (Commonwealth of Australia (Geoscience Australia) 2018).” Source: Hughes, T. P., et al., 2018


In addition to coral bleaching, cyclones and crown-of-thorns sea star outbreaks have been the main cause of decline in coral cover on the GBR within the past four years. The northern area of the GBR is expected to have lost about half of its’ coral cover. This estimate reflects the impacts of two episodes of severe coral bleaching from 2014-2017 and two cyclones.  The central reef has experienced a decline in coral cover from 22% in 2016 to 14% in 2018 due to coral bleaching and the ongoing southward spread of the crown-of-thorns sea star. Even though the southern portion of the GBR was not exposed to the 2016/2017 warming events, coral cover has dropped from 33% in 2017 to 25% in 2018. On the southern reefs, the crown-of-thorns sea star outbreaks appear to be the main cause for the most recent decline.


During my last trip to Australia, I assisted in injecting vinegar into the crown-of-thorns sea stars at Lodestone Reef on the GBR. The vinegar kills the sea star within 24 hours potentially reducing their threat to hard, or stony corals. Photo Credit: Chris Jones


“Clearly the reef is struggling with multiple impacts,” says Prof. Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies. “Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: 1°C of warming so far has already caused four events in the past 19 years.”

“Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.”



[1] Coral bleaching – Coral bleaching occurs when the relationship between the coral host and zooxanthellae (photosynthetic algae, NOAA), which give coral much of their colour, breaks down. Without the zooxanthellae, the tissue of the coral animal appears transparent and the coral’s bright white skeleton is revealed. Corals begin to starve once they bleach. (GBRMPA)


Additional Resources:

Ekwurzel, B., Boneham, J., Dalton, M. W., Heede, R., Mera, R. J., Allen, M. R., & Frumhoff, P. C. (2017). The rise in global atmospheric CO2, surface temperature, and sea level from emissions traced to major carbon producers. Climatic Change144(4), 579-590.

Hughes, T.P. & Kerry, J.T. Back-to-back bleaching has now hit two-thirds of the Great Barrier Reef. The Conversation (2017)

Hughes, T. P., Kerry, J. T., Baird, A. H., Connolly, S. R., Dietzel, A., Eakin, C. M., … & McWilliam, M. J. (2018). Global warming transforms coral reef assemblages. Nature556(7702), 492.

Media Release: Two Thirds of the Great Barrier Reef hit by back-to-back mass coral bleaching

Long-term Reef Monitoring Program – Annual Summary Report on coral reef condition for 2017/2018


#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!