Who I amI was born in one of the largest cities in Africa, but grew up with the innate desire to seek wild places. I love the ocean for its wildness and as a kid the idea that there was this completely untamed place without barriers or fences on my doorstep, a place where I could explore on my own, captivated me. From a young age, after my family moved to the coast, I spent every spare moment surfing, diving and exploring the shoreline and rock pools of South Africa.
I didn’t want to stop exploring, so at university I decided to study zoology and oceanography. But I quickly discovered that studying the ocean didn’t necessarily involve being in the ocean or even being at sea. I wanted to immerse myself, literally, to observe my study subject at first hand in the wild rather than under a microscope. And as an ocean-user, I wanted to study something that I felt a deep respect for. There was no better subject than sharks. In my years of diving and surfing, I’ve had many encounters with sharks. In all those encounters, a sense of fascination has always outweighed any fleeting fear. I’m motivated by my love for wild places and my fascination for sharks. As a shark researcher, my aim is to preserve the integrity of the systems that I love.
Where I workOur study site lies within Africa’s first transboundary marine protected area. It straddles the international border between South Africa and Mozambique and is fringed by the world’s highest vegetated sand dunes along some of the most pristine coastline in southern Africa. It is an exceptional place, with high-latitude coral reefs and a remarkably diverse array of large shark species.
A typical day in the field starts with the launching of Chance, our trusty rigid-hulled inflatable boat, from a sandy beach and through breaking surf before we navigate 10 miles (16 kilometres) along the coast and 2–3 miles (3–5 kilometres) offshore. The objective is to find a tiger shark. Many people think that the ocean is teeming with sharks, but finding a single shark in the wide expanse is often exceptionally challenging. Because tiger sharks are highly mobile, occurring within a huge area, we spend a lot of time searching for them and waiting for ideal conditions: warm, clean water and a north–south current. We also spend a lot of time diving to get an idea of the changing conditions and of where the sharks are. It is often during this time spent in the water that we witness the things that make our study site so special. On any given day we may encounter between six and 10 species of sharks, as well as massive fish aggregations, manta rays, ancient leatherback turtles and migrating humpback whales. Among all of this is where we find tiger sharks and discover more about them.
What I doOur research seeks to answer the question of the balance between the refuges of marine protected areas and the risks faced by tiger sharks throughout the south-western Indian Ocean. Because of their roaming nature, it is likely that the tiger sharks we locate at our study site spend a considerable amount of time outside the marine protected areas we find them in, and are thus probably exposed to risks such as unregulated shark fishing or shark culling programmes. We use data from telemetry and genetic analysis to examine this balance between refuge and risk.
Before we can start the science, though, we need to access the sharks. With the generous support of a scientific grant from the SOSF, we’re able to access our study site, a remote and challenging spot known for its tiger sharks, which otherwise would go unstudied. With the means to access these sharks, we are able to tag them. Using short-term satellite transmitters and longer-term underwater transmitters, we can track the habitat use and migration patterns of tiger sharks.
In the short-term the satellite transmitters give us a broad idea of tiger shark movements, whereas over time the fine-scale data from the longer-term underwater transmitters enable us to understand more about the conservation status of these sharks in relation to their refuges and risks. Additionally, we use genetic analysis to determine the links between various regional and global populations of tiger sharks. This in turns helps us to quantify the level of risk that tiger shark populations are exposed to and determine the current conservation status of the species. Finally, we can use this information to propose ways in which to reduce the risks that these sharks face and improve current conservation management practices within and outside marine protected areas in the region.