School of Biology, University of St Andrews

Tag: skate

On-the-ground conservation of the Critically Endangered flapper skate: a synergy of citizen science, cutting-edge research and governance

The early morning sunlight glistens gently on the still, deep-blue waters of Dunstaffnage Marina. I’m walking along the pontoon, pushing a heavy cart of equipment down to the boat we’ve hired for the day: the Blue-Fin. The awesome mountains of the west coast stand around us; speckled snow glints on some of the tallest peaks. The nose of Ben Cruachan pokes out of the clouds for a moment, its full face then coming into focus. It’s a view you can’t beat and one of my favourite places in the world.

Scotland is a beautiful place to work, when it isn’t raining

I’m not just here for the view though. You may be aware that populations of elasmobranchs (sharks, skates and rays) around the world have experienced worrying declines. But you might be less aware that there are also incredible, large and threatened elasmobranch species closer to home. We’re here for one of Britain’s largest and most threatened marine species: the Critically Endangered flapper skate (Dipturus intermedius). Growing up to about two and a half metres in size, and weighing up to one hundred kilograms, the flapper skate is a hidden wonder in British waters. Once found from the Mediterranean to northern Scandinavian, the flapper skate was fished almost to extinction – even becoming the first marine species to be declared ‘locally extinct’. But the skate persist in a few small pockets of their former distribution. And one of those is on the west coast of Scotland, where a remarkable and inspiring synergy of citizen science, cutting-edge research and governance is turning the tide. I can’t quite believe I’ve become part of the story. 

Panting slightly, I draw up the heavy cart at the boat. In the humongous, neon-yellow oilskins and bright yellow boots I’ve borrowed for the day, I feel like a ludicrous clown, or perhaps a lollypop. Bending over, I start to lug equipment over the side of the boat: ultra-sound monitors, tape measures, a water pump, hose piping, electronic acoustic tags, a blood composition monitor, antiseptics, anaesthetic, syringes, and litres and litres of water – it all has to go in. Everything we need in the field to catch, health check and tag flapper skate.

How do you catch a one-hundred-kilogram fish? Amazingly (at least for someone with as much fishing experience as me), with a hook and line. Indeed, recreational anglers started the practice of catch-tag-and-release for flapper skate decades ago – tagging individuals with uniquely identifiable tags, so that the capture histories of specific individuals could be mapped across space and time. This pioneering practice has been one of the most valuable sources of information available to scientists and policymakers regarding the flapper skate. In particular, it has shown that the same individuals are caught again and again through time, suggesting that some skate are resident in the same area or at least frequently turn again and again through time. This was the major insight that led to the designation of the Loch Sunart to the Sound of Jura Marine Protected Area, the only body of water in UK waters currently designated specifically for the conservation of an elasmobranch. However, despite the enormous value of these capture-recapture data, they don’t tell us about where skate go and what they do in-between recapture events. And that’s why we’re back in the Marine Protected Area today.

This is my first time on the fieldwork team, and I’m not quite sure what’s coming. The boat’s engine comes to life and we chug slowly out of the marina. The wind starts to pick up and the sun slips behind a cloud – typical Scotland! Shivering slightly, I pull my oilskins a little tighter, feeling ominous about the weather. We round the bend, out of the marina, and the boat begins to pick up pace. The wind’s rushing past my face, turning my ears and cheeks pink with the cold. A dash of sea spray catches me in the face. I steady myself as the boat begins to sway, grinning in the excitement: we’re off!

Home for the day and the clouds have rolled in over Mull

We’re heading South, travelling down a deep channel to an area where skate are often found. Our aim is to catch, health check and tag flapper skate with acoustic transmitters. These tags transmit individual-specific acoustic pings every so often, working in combination with an array of underwater acoustic receivers (special hydrophones) which listen continuously for acoustic transmissions. When a skate moves into the detection range of a receiver, the receiver logs any detections and later, we can work out where the skate were and where they like to be using cutting-edge statistical modelling. That’s actually my job as part of a PhD studentship, funded jointly by Scottish Natural Heritage (through the Marine Alliance for Science and Technology in Scotland) and the Centre for Research into Ecological and Environmental Modelling in St. Andrews. I’m here today, though, thanks to valuable support from Shark Guardian.

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Ed Bringing up his first skate

We’ve reached our site, the anchor has been deployed, the rods baited, and the reels are spinning furiously as the weights sink towards the bottom. It’s nearly 200 m deep here. Vets from the Royal Zoological Society of Scotland, Edinburgh Zoo; Adam and Georgina, are full-stations-go, checking over equipment and rehearsing protocols for when (if!) we catch a skate. Suddenly, that seems to be happening already: a rod’s nodding and Roger (our skipper) is on it, reeling it in to keep the tension, while I don a waist harness into which the rod is clipped. I feel a pull on the harness and realise that my job is to carefully bring the skate to the surface.

We use rod and line to capture skate (as opposed to long-lining) because it means that we only catch one skate at a time. Consequently, skate are brought to the surface as soon as they are caught, minimising the time that they spend on the hook. Barbless hooks also reduce the risk of damaging the skate’s mouth. Bringing the skate up isn’t easy, though, because skate initially anchor themselves to the seafloor when they are caught, before swimming up through the water column.  It’s several minutes, and my back is starting to ache, but I finally I feel the skate release the bottom. I start to reel it in, slowly, to avoid bring the skate up too quickly through the different temperature zones in the water column. Sometime later, the skate breaks the surface. It’s a small juvenile female and the first one I’ve ever seen.

Checking the heart beat of the skate, while keeping water flowing over the gills.

Using a specially-designed sling system, we carefully lift the skate onto the deck and rest it on a support pad to make sure that it is as comfortable as possible. A custom-made water pump drives oxygenated sea water through a system of hoses into the skate’s mouth so that it can breathe and the vets are straight to work, scanning the skate for scrapes and marks and taking blood samples for analysis, before surgically tagging the skate under local anaesthetic. This is a remarkably quick and simple procedure, taking just a few minutes. Meanwhile, Jane (SNH skate expert) and I are monitoring the respiratory and cardiac function of the skate; at the moment, I’m measuring the breathing rate (a breath is visible when water is pumped over from the gills) and Jane’s monitoring the heart rate by counting the number of heart beats from real-time ultrasound imaging of the heart.

The tagging is complete and it’s time to measure and photograph the skate. The photograph will be uploaded to Skatespotter: an online database that contains pictures of a large number of skate. Together with the capture-recapture data, this helps us to record the recapture history of skate, their appearance and changes through time, examine parasite loads and timing of biological events (such as pregnancy); all valuable information that can guide management.

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A rare glimpse of Europe’s largest skate species

It’s only been 15 minutes, but the skate is back in the water. I watch it flap it huge graceful wings, turning slightly as it descends once more into the depths. I suspect I won’t see that one again for a while. But, perhaps, soon enough, we’ll see it start to transmit signals to acoustic receivers that will tell us how it’s using the Marine Protected Area in years to come. I look up, panting slightly. The sun is shining, and another rod is starting to tick…   

Bibliography

Edward Lavender is a PhD student at the University of St Andrews and a member of the Marine Alliance for Science and Technology in Scotland Graduate School. Edward acknowledges his PhD funders (Scottish Natural Heritage and the Centre for Research into Ecological and Environmental Modelling) and extends his thanks to Shark Guardian for providing the funding for his participation in the ongoing fieldwork project, designed to monitor skate habitat use in the Loch Sunart to the Sound of Jura Marine Protected Area. You can read more about the flapper skate here.

Tagged flapper skate findings presented at International Conference on Fish Telemetry

PhD student, Edward Lavender, recently presented some of his surprising early findings about the detection patterns of Critically Endangered flapper skate within an array of static acoustic receivers in a Scottish Marine Protected Area at the 5th International Conference on Fish Telemetry, Arendal, Norway (June 2019).
Tagged skate were almost entirely detected around a small set of receivers in the south of the Marine Protected Area. But is this really where they ‘like’ to be? And does this mean their movements are restricted?
Unfortunately, detections at acoustic receivers represent an unknown combination of animal movement, the spatiotemporal distribution of receivers (i.e. sampling effort) and detection probability. For flapper skate within a highly non-uniformly distributed receiver array, this means that detection patterns, alone, tell us very little about space use. Fortunately, however, high resolution depth data were collected alongside acoustic data for some individuals. In addition, skate are bottom dwelling and, off the West coast of Scotland, live in a bathymetrically heterogeneous environment. This raises the enticing possibility of estimating movement pathways between acoustic detections using depth data as a way of circumventing these challenges to address the questions posed above.

At the conference, Edward presented the first version of such an algorithm, creating the opportunity to study the movement patterns and space use of demersal species within similar systems in a way which isn’t so constrained by the design of the receiver array and at higher spatial (5 m) and temporal (2 minute) resolutions than previously possible. For the flapper skate specifically, Ed’s research opens new doors to investigate their movements in relation to the Marine Protected Area.

The International Conference on Fish Telemetry is a forum to discuss research on the application of tagging technologies to study fish biology. This year, researchers from over 20 countries came to Arendal – a small municipality in the far south of Norway – to give posters, presentations, meet colleagues and extend the boundaries of knowledge.
This context, set within a spectacular Nordic fjordic system, fostered an atmosphere buzzing with ideas, excitement and discussions spanning the conservation physiology of Atlantic salmon and spatial management of threatened elasmobranch populations to cutting-edge model development, open data and more.

Edward Lavender is grateful to Shark Guardian for supporting this research and his attendance at the conference.
If you would like a copy of the poster or more information please contact Edward.