Photo by Morne Hardenberg | © shark explorers
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False Bay, South Africa

Sharks on the urban edge

False Bay is home to one of the world’s largest white shark populations and a growing human community. This creates a number of challenges for both people and sharks. Alison is finding out how these apex predators shape the bay and what would happen if they disappeared.

Project Leader:

Alison Kock

‘My goal is to be a marine biologist.’ This is the hand-made banner that I displayed above my desk all through high school. I have always wanted to be a marine biologist and was fortunate to have parents who fostered my love for the ocean. When I was very young I used to accompany my dad on boat trips to harvest crayfish. We would spend hours at sea, deploying nets and waiting for the crayfish to climb inside. When we…


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Status:

Active

Years active:

2015

Species:

Sharks

Partner organisations:

The Shark Spotters

Project details

Project Leaders

Alison Kock

Who I am

‘My goal is to be a marine biologist.’ This is the hand-made banner that I displayed above my desk all through high school. I have always wanted to be a marine biologist and was fortunate to have parents who fostered my love for the ocean. When I was very young I used to accompany my dad on boat trips to harvest crayfish. We would spend hours at sea, deploying nets and waiting for the crayfish to climb inside. When we retrieved the nets, it wasn’t only crayfish that we found, but small shysharks too. The little sharks would curl up into a ball with their tail covering their eyes and my dad instructed me to kiss them on the head and gently release them back into the water. When I did so, the shysharks would uncurl and swim back down to the bottom.
After high school I enrolled at the University of Cape Town to pursue my career in marine biology and at every opportunity I spent my free time scuba-diving and exploring the incredible underwater world around Cape Town. After my undergraduate degree I had the opportunity to go out on a white shark viewing trip to Seal Island. That was the first time I saw a great white shark launch itself two metres into the air chasing a Cape fur seal. I was hooked. I decided then and there that I was going to be the one to discover the answers to all the questions nobody could answer.
Following a four-year period when I worked as a field guide on the ocean with the sharks and in the terrestrial environment with other wildlife, I went back to university and initiated a research project on the behavioural ecology of white sharks in False Bay, which was one of the six inaugural projects funded by the Save Our Seas Foundation. Seventeen years since my first great white shark sighting, I am still studying these sharks, now in the role of research manager for Cape Town’s pioneering Shark Spotters programme. I no longer kiss the sharks on the head, but I did achieve my goal and have my dream job.

Where I work

Cape Town, South Africa, is a major city with an ocean wilderness as a backyard. It encompasses False Bay, a special place where you can visit African penguin colonies, view massive southern right whales breaching up to 15 times in a row from shore, encounter thousands of common dolphins on a boat trip, watch fishermen hauling in nets filled with yellowtail and, if you’re lucky, sit at a mountain lookout and watch great white sharks swim lazily by.
Just six kilometres from the coast is a small granite island that is home to 70,000 Cape fur seals at the peak of the season. It is here that you can witness the incredible raw power of the sharks as they pursue their seal prey in a game of survival. Nowhere else on earth can these encounters be observed with such consistency and it is a spectacle that deserves to be preserved.
One of the best things about working in Cape Town is that it is a hop, skip and a 20-minute boat ride to get to my field sites. This means that I can regularly and consistently conduct field work throughout the year. So far, my team and I have established that False Bay is a critical area for the conservation of white sharks because a significant proportion of South Africa’s white shark population uses the area throughout the year. But the sharks’ high fidelity to this coastal area has implications for them, as the environment is heavily impacted by fishing, pollution and disturbance resulting from coastal development. It also has implications for the large proportion of Cape Town’s four million residents who swim, surf, kayak, windsurf, kite-board, fish and dive along these shores. Shark incidents have increased over the years and conserving a threatened apex predator in conflict with people is a major conservation challenge. To maintain the balance between white shark conservation and public safety, I believe it is imperative that we have a strong scientific foundation on white shark ecology and behaviour, coupled with non-lethal mitigation methods to reduce shark incidents and supported by a comprehensive education and awareness strategy.

What I do

My role is to conduct applied research on the ecology and behaviour of Cape Town’s white shark population. So far my team and I have answered questions relating to the ‘when’ and ‘where’ of white shark occurrence. We have discovered that they are present all year round in False Bay, but use the bay very differently depending on the season. In autumn and winter, male and female sharks spend most of their time around Seal Island, preying on naive seal pups. However, come spring and summer, the sharks spend little time around the island and instead many of the female sharks move inshore, closer to the coast.
Although we have a good understanding of why white sharks visit the island, our understanding of why they spend so much time inshore is still limited. We do know that within the inshore area there are specific hotspots, like the northern shores of False Bay, which are used significantly more than other inshore areas. But we don’t know what makes the inshore area so attractive. We have also determined that most of the sharks are juveniles and sub-adults.
My research now focuses on the ‘why’. To achieve this goal I will use a combination of direct observation, photo-identification, acoustic monitoring and animal-borne cameras. With a hypothesis-driven approach, I will investigate the drivers of white shark presence in False Bay, both environmental (such as water temperature) and biological (such as prey availability). This will enable us to model which factors relate to high shark activity and can be incorporated into shark safety strategies.
Furthermore, I will examine the interactions between white sharks and their prey to define the species’ ecological role in a temperate ecosystem. Predators can shape the ecosystems in which they live in a direct way by reducing prey numbers, which in turn can affect populations lower down the food chain. They can also influence the structure and function of the ecosystem by causing prey populations to modify their behaviour in response to predation risk. I hope that with enough information we can predict what would happen to the ecosystem if their populations changed significantly.
The overarching goal is to contribute to the conservation of the South African white shark population, its critical habitats and its prey resources. Even though white sharks have an extensive range, their high site fidelity to False Bay gives us an opportunity to contribute to the long-term conservation of this critical habitat and continue to foster co-existence between people and sharks.

Project Details

Shark research component of the Shark Spotters programme

Key objective

The key objective of this research is to understand the drivers, both environmental (e.g., water temperature) and biological (e.g., prey availability), of white shark presence in False Bay and define the role of this apex predator in a temperate ecosystem. We will use the results to improve management of critical habitats, and in shark safety strategies and awareness campaigns.

Why is this important

It has been established that there is high spatial overlap between human recreational water-users and female white sharks in False Bay during the warmer months of the year. The white shark’s seasonal distribution along popular recreational coastlines, natural opportunistic predatory tactics and large size increase the potential for human-shark conflict. This results in the challenge of conserving a threatened and protected apex predator in conflict with humans.
Although Cape Town is a white shark conservation success story, conflict between humans and sharks is likely to continue, due to human population growth and increased coastal development. Therefore, to maintain the balance between white shark conservation and public safety, it is imperative that we have a strong scientific foundation for white shark ecology, coupled with non-lethal mitigation methods and supported by a comprehensive education and awareness strategy.

Background

Previous research has identified False Bay is a critical area for white shark conservation because both sexes, across a range of sizes, show high fidelity to the bay. Furthermore, it’s been shown that Seal Island hosts one of the world’s largest white shark populations. The past 10 years of research has described the spatial ecology of white sharks in False Bay and identified the sites and times of high and low shark presence and activity. In autumn and winter, males and females aggregate around Seal Island where they feed on young-of-the-year seals. In spring and summer, there is marked sexual segregation: females frequent inshore areas and males are seldom detected in the bay. This research has added substantially to our knowledge of white shark ecology and conservation challenges. However, what drives this behaviour, especially in inshore areas, is still not well understood.
Previous research demonstrated that the primary function of Seal Island is most likely as a feeding aggregation site. Over the past nine years, sightings per unit effort have varied across years; some years have had relatively lower numbers of sightings, and others have had higher numbers of sightings. What drives this annual variation is not well understood. It is also important to understand the primary function of this inshore region for white sharks, especially maturing females, because the area is heavily affected by anthropogenic disturbance, such as fishing, pollution and coastal development.
A major gap in our knowledge is an understanding of the ecological role of white sharks in local ecosystems. Predators can shape the ecosystems in which they live in a direct (lethal) way by reducing prey densities or in an indirect way (non-lethal) manner as anti-predator behaviour may manifest as changes in resource use by prey.

Aims & objectives

The aims and objectives of this project are to:

  • Monitor white shark presence and distribution in False Bay across different habitats and seasons, and compare their behaviour, e.g., swimming depth and speed, in different habitats to understand how the sharks use them, i.e., for feeding, resting or socialising.
  • Monitor population demographics (size and sex ratios) and dynamics, across seasons and years at Seal Island and inshore.
  • Monitor trends in sightings and population status over time to determine whether the population is stable, increasing or decreasing.
  • Identify environmental conditions affecting white shark presence and distribution. Additionally, test the hypothesis that white shark presence inshore during spring and summer is higher when the water is warm (≥18 °C) and during the phase of the new moon. We will compare this with behaviour observed at Seal Island.
  • Identify prey availability (diversity and abundance) across different habitats and seasons in False Bay. We will test the hypothesis that white shark presence is related to an increase in abundance of teleost and chondrichthyan prey in spring and summer months.
  • Identify the diet of white sharks, their trophic position and food web interactions. Define the ecological role of white sharks in False Bay to understand the top-down control they exert on local ecosystems, and ultimately be able to predict what would happen to the ecosystem if their populations declined significantly.