In the Field: Basking Sharks
SHOW NOTES
We meet Alex and the team at the harbour, just down the road from a small town in western Ireland where the boat is moored [2.25]. Joining us are skipper Nick and director of the Big Fish Lab Dr Taylor Chapple. Taylor has over 15 years of experience studying sharks – in particular their movements, behaviours and population dynamics. Alex began working with Taylor following her PhD, and now works as a postdoctoral researcher at the Big Fish Lab.
Together, Alex and Taylor are hoping to get as much data as they can in the very short weather window that they have; Ireland is not famed for long periods of settled weather, and currently we have just under a week of sunshine and low wind. In order to make the most, Alex and Taylor haven’t slept – they stepped off a plane from the U.S. just the previous night! But despite the jet lag, they are ready to jump straight into work. We pack the boat full of equipment – a number of interesting looking painter’s poles with various attachments, waterproof containers, toolboxes and an ultrasound machine – and once Nick is happy, accelerate off into the bay in search of sharks.
But while we’re searching and getting everything ready, let’s find out more about Alex and her research [4.53]. Alex grew up in Cincinnati, Ohio, a landlocked city in the middle of the U.S. She had always loved working with animals, and was fascinated by the ocean. She remembers family holidays to Florida, where her interest in the marine environment flourished. But it wasn’t until the age of 12 that Alex learned of marine biologist as a profession. She set her sights on becoming just that, but her journey into the world of shark science is a little more niche! Alex actually started out being scared of sharks, watching documentaries about them on the TV. Her decision to study them was actually a way of coping with that fear – and it’s fair to say that she has been very successful at doing so!
Alex now works with some of the largest shark species in the world [6.55]. Her background is in animal behaviour, which was the focus of her PhD at UC Davis in California. This means she does a lot of work tagging and tracking animals, studying their movement patterns and trying to understand the drivers behind these movements. She also is interested in their diet, and how this influences where they are going. And, more recently, Alex has been investigating their social behaviour. “That’s actually a passion of mine.” She says. “Because I think, given the stigma that has surrounded sharks, historically of these mindless man eating machines, this concept that they can form complex relationships is really cool.”
Alex works with many different species – from chinook salmon and salmon sharks for Oregon State University, to spiny dogfish for her Save Our Seas Foundation project Missing the Target? Refining spiny dogfish fisheries surveys. But today, we are heading out to research basking sharks, the second largest species of shark in the world. They are the biggest species Alex works with, and one very close to her heart. She began studying them for her PhD, and is now co-coordinator of the Irish Basking Shark Group (IBSG).
Speaking of basking sharks, it isn’t long until we find them in the field [8.47]. Just ten minutes into our journey, we begin to see enormous, triangular dorsal fins slicing through the water, followed by an equally large caudal fin swishing back and forth. And they are everywhere. At one point, we are surrounded by almost ten individuals, all feeding placidly in the same spot. Basking sharks can reach lengths of up to 12 metres (39 feet) and can weigh up to four tonnes. They are actually related to the great white shark, as they are part of the order Lamniformes – the mackerel sharks. But unlike a great white, basking sharks exclusively feed on zooplankton – tiny organisms that drift in the water column. Basking sharks are ‘filter feeders’, and as such lack large rows of teeth. Instead, they have filtering mechanisms, known as gill rakers, that encircle their head and catch plankton as it enters the mouth with the surrounding seawater. The water flows out the shark’s gills, but the plankton remains stuck in the sieve-like structure. Such a diet means that you can often find basking sharks swimming right at the water’s surface, so that their distinctively bulbous nose pokes out!
Now we’ve found the sharks, it’s time to start researching [17.02]. Alex and Taylor begin rushing about the boat, putting various parts of equipment together and making a plan for the day. As the sharks are sitting nice and high in the water, we’re going to start with tagging [23.49]. A tag is essentially an animal fitbit – it’s a package that gets attached to the shark’s body, and captures data on their movements, behaviour and the surrounding environment. The problem is, basking sharks are so large that, unlike other shark species, you can’t capture them and bring them on board to attach a tag. Taylor and Alex had to build a specially designed tagging pole to allow them to attach a tag to a basking shark over the side of the boat, and then work out how to use it – something that has taken them a few field seasons to get right.
Once a suitable shark has been located, Alex and Taylor need to work fast [28.02]. Nick will line up the boat beside the shark, and either Alex or Taylor will get in position at the bow with the tagging pole, and once they are almost on top of the shark, use the pole to attach the tag just behind the shark’s dorsal fin. Whoever wasn’t tagging will then use another pole with a GoPro attached to get footage of the tagged individual, looking underneath the shark to look for the presence of claspers (indicating a male) or absence of claspers (a female). All this happens within the space of a few minutes – it’s quick, efficient, but stressful.
In our day in the field, we managed to successfully deploy tags on five individuals [30.23]. While it doesn’t hurt the shark, they do sometimes have a knee-jerk reaction, swiping their huge, muscular tails and diving (which often means a big splash for those of us on the boat!). It’s more a case of the shark getting a fright than a response to pain. After tagging, Alex and Taylor observe the shark to make sure they return to the surface and resume feeding – and for the most part, the shark has done exactly that. “Tagging in general, across all shark species – across any animal – has an effect to some degree. But we’re pretty confident that they’re able to at least resume a lot of their normal behaviours within a brief period of time.” Says Alex.
Something else that Alex is interested in doing is investigating what is bringing the sharks to the area, so after tagging we do a little bit of ‘active tracking’ [32.48]. This involves lowering something called a directional hydrophone into the water, which picks up the signal being transmitted from the shark’s tag. This is attached to a device that makes a kind of pinging sound, which gets louder when you point it in the right direction. A bit like that game where you search for something, and someone shouts “hotter” or “colder” at you, depending on whether you’re looking in the right area! Once we worked out the right direction, skipper Nick then followed the shark very slowly, moving in a zig-zag pattern. At the same time, Taylor is watching the echosounder – another device that helps to understand what is beneath the boat. They are mainly used to estimate the depth of the seabed, to assist in navigation, but they can also detect objects in the water column, such as a particularly dense patch of plankton. Taylor and Alex are trying to understand if the area in which they found the shark is in one of these patches, information that might be used to predict where basking sharks will occur.
And if that wasn’t enough, Alex is also attempting to ultrasound the sharks [38.35]! For this, she has been working with renowned expert in reproductive physiology James Sulikowski. The basking sharks that return to Ireland are often mature females, which begs the question: could they be pregnant? This would be very valuable information to have, given that very little is known about the basking shark reproductive cycle. And there is only one non-invasive way to find out: ultrasounding.
While in the field, we see Alex and Taylor experimenting with this for the very first time [40.12]. Again, Nick expertly manoeuvres the boat so that they are slowly drifting beside a swimming shark. Taylor then leans over the side, gently lowering the probe of the ultrasound into the water and directing it at the flanks of the shark. Meanwhile, Alex is watching the screen of the ultrasound and directing him: “a little upwards…no, lower now!”. They are trying to locate the shark’s uterus, to see if she has any pups. It’s all a learning curve, and the first few times, Alex sees nothing. But, later in the day, she cries out excitedly [43.40] – “I think I just saw something different!”. What that something was, we won’t know until she gets back to the lab and reviews the footage – but it’s very exciting nonetheless.
Lastly, we have a go at monitoring some social behaviour [44.13]. Basking sharks aren’t typically considered a social species, and most aggregations are opportunistic, formed when multiple sharks take advantage of the same patch of plankton. But, some exciting discoveries have been made in recent years that potentially demonstrate social activity, including ‘courtship tauruses’ – groups of basking sharks swimming in circles, almost nose-to-tail, in what is thought to be a pre-mating behaviour. “When I would come to Ireland and see them here, they were very rarely alone.” Alex explains. “We often see them swimming next to each other in what’s called parallel, like literally right next to each other in sync. We also see them following each other a lot. And we’ve also seen them swimming in formation, kind of like geese and a giant group, multiple sharks deep with a point at the end, kind of like a V. And you have to ask why.” Alex is hoping to use something called a ‘proximity logger’ to study these interactions, and find out who is interacting with who, and if there is a pattern to it. It would almost be like Facebook for sharks!
We return from our day in the field with (hopefully!) a boatload of data [47.57]. And this is all information that could potentially be used in the protection of basking sharks – an Endangered species. Basking sharks are now a protected species in some parts of the world, but they were previously targeted heavily by fisheries for their large, oily liver. Although direct fisheries for basking sharks have now ceased, the impacts of over-exploitation are still apparent in the population – basking sharks are thought to be slow-growing and slow to reproduce, and so it will take the population some time to recover. There are also more current threats to basking sharks, including by-catch, the fin trade, and marine pollution. But, as so little is known about them, it is difficult to know where these threats occur, and how severe they are. Alex’s work – and the work of her collaborators, including Taylor, The Big Fish Lab, and the Irish Basking Shark Group – will go some way to understanding these mysterious animals, and just how important Ireland is to them.
“I think Ireland is perhaps one of the last safe haven safe havens for this population, and and perhaps even the species globally.” Alex says. “It’s really hard to attribute a single country to the persistence of a population because these animals are so mobile…the same ones in Ireland are often going to Scotland [or to] England, sometimes going out to Africa, or Cape Cod, right. So they don’t recognise regional boundaries in the same way that we do. But this habitat where we have found them, I think, is critical.”
ABOUT OUR GUEST
DR ALEXANDRA MCINTURF
Alex McInturf is a CICOES postdoctoral fellow in the Big Fish Lab. Born and raised in Cincinnati, Ohio, she attended Williams College for her undergraduate education. Following graduation, she was an intern with Oceans Research (South Africa) and the Bimini Shark Lab (Bahamas), where she studied white sharks, tiger sharks, hammerhead sharks, and sandtiger sharks. She obtained her PhD in Animal Behaviour from the University of California, Davis, for which she examined physiology, behaviour, and distribution of basking sharks, sevengill sharks, and salmon. Alex is co-coordinator of the Irish Basking Shark Group (IBSG). In addition to research, Alex is an avid science communicator, soccer player, cyclist, weight lifter, reader, baker, and dog mom.
Websites: https://alexandramcinturf.squarespace.com, https://marineresearch.oregonstate.edu/chapple-lab, https://www.baskingshark.ie/, https://saveourseas.com/project-leader/alexandra-mcinturf/,
Social media: Alex (@drsurfnturf), Big Fish Lab (@big_fish_lab), Irish Basking Shark Group (@baskingirish)
