David Sims

Who I am

From the house on the south coast of England where I was born and grew up, it was only a few minutes on foot to the beach. It was a journey I made over and over again, every time I could. Countless days were spent in the cool waters of the English Channel, swimming, snorkelling, boating and exploring the pools in search of marine life, particularly sharks. Before that – and, according to my parents, from the age of about four – all I did was draw sharks and collect images of them. So all through those early years, the nearby sea and the creatures that lived in it were a central part of my world. It was only later, once I had started scuba diving at the age of 16, that I realised it was actually the other way around: what I really wanted was to be part of their world. Then a chance encounter with a giant, plankton-feeding basking shark that glided effortlessly past on its journey, disappearing as quickly as it had arrived, propelled me on my own journey to become a marine biologist and a shark scientist.
After studying for a degree in marine biology at university followed by a PhD in shark behavioural ecology, in 1994 I returned to a question I had posed many years before: where do basking sharks go and what do they do? I then spent the next 12 years in their world, studying them in many locations around the north-eastern Atlantic Ocean, spending hours, days and months on research vessels tracking their movements and sampling what they were feeding on. This way of learning about sharks and what we find out continue to fascinate and motivate me in equal measure.
Moving from Aberdeen University in Scotland to the superb laboratory of the Marine Biological Association (MBA) in Plymouth, south-western UK, as a research fellow 15 years ago has enabled me over the ensuing years to build a research team of talented and enthusiastic scientists. The sole focus of the group is to study shark and ray behavioural ecology to inform conservation – what we do is who I am.

Where I work

Our laboratory is the open sea. Depending on what species of shark or ray we are studying, it might be the Atlantic, Indian or Pacific Ocean. In this pelagic laboratory we search for sharks and rays, using our increasing knowledge of their behaviour and habitat preferences to lead us to the most likely places where they choose to hang out. When we find them we attach electronic tags to eavesdrop on their behaviour in their watery world, sometimes for as long as several years.
Over the past 20 years my research group has tagged hundreds of sharks and rays all over the globe, including shortfin mako, blue, porbeagle, bull and silvertip sharks, and common skate and thornback rays. But it is our research on the blue and mako sharks that takes us into the heart of the blue ocean. Finding the hotspots of adult makos, for instance, requires exploration of the remotest places, from the mid-Atlantic Ridge to tropical sea mounts, where in any direction the nearest land can be thousands of kilometres away. There’s nothing boring about horizon after horizon of just sea – at least not for me. The ocean is never the same on any two days; nor are the incredible animals you see along the way, such as the strange-looking ocean sunfish (the world’s heaviest bony fish), or migrating leatherback turtles or baleen whales that are just passing through.

What I do

My goal has always been to use our new tracking technologies not only to reveal the amazing lives of sharks, but also to use this knowledge to better protect them.
For the past eight years one of my team’s principal projects has been on a highly vulnerable shark, the shortfin mako – the fastest shark in the sea, clocking speeds of 50 kilometres per hour (more than 30 miles per hour).
The shortfin mako is threatened because it is the second most exploited pelagic shark taken by long-line fishing vessels – and there are no international limits on open-ocean catches. This, coupled with its late sexual maturity (18 years in females) and relatively low fecundity (4–18 pups every two or three years), makes it less resilient to fishing and more susceptible to the effects of overfishing. Indeed, studies where good quality data are available show declines in the abundance of Atlantic makos.
What surprised us, though, when we started the study was that very little was known about the species’ movements and space use, its migrations and habitat selection, or its overlap with fishing vessels in space and time. Knowing where makos prefer to be, when they move on, and how much and for how long their space use overlaps with fishing effort is crucial information for assessing the likelihood of overexploitation and the need for, and scale of, conservation measures. After all, you can’t adequately conserve a species if you don’t know where it is.
With this in mind, we aim to track large mako sharks in the blue ocean across the species’ entire North Atlantic range. We have tagged large males and pregnant females in the mid-Atlantic with new satellite transmitters so that we can follow these ocean wanderers for a full annual cycle, with the objectives of determining their foraging grounds and breeding migrations and of highlighting the ocean areas critical for pupping. The shark tracks are analysed in relation to remote sensing data of the ocean, such as temperature, primary productivity and ocean weather, and then passed through mathematical models to identify which habitats the sharks prefer over others that are available. We have designed the tags to withstand immense pressure because in our previous SOSF-funded study we discovered that makos dive to a depth of more than 1,500 metres (about 5,000 feet) and often several times per day! Why they go that deep is another mystery we are aiming to solve.
A key target in this project to find out how much of the space used by makos is also exploited by long-line fishing vessels. Are makos essentially tracked by fishing effort all year round or are there periods or habitats in which sharks and boats don’t cross paths? This aspect of the project will be made possible with a unique data set we have assembled: the satellite-tracked movements of the entire Spanish and Portuguese long-line fishing fleets for 10 years. Relating the satellite tracks of makos with those of the vessels will reveal if the sharks really do have no place to hide.