Cape Town (CNN) — From above, it looks like a vast oil spill spreading across the ocean. It's been called the "Greatest Shoal on Earth" and it's one of the planet's biggest migrations in terms of biomass.
Along South Africa's east coast, between May and July, billions of spawning sardines travel north towards Mozambique. They are pursued by predators ranging from sharks to dolphins, whales and even humans.
Before the Covid-19 pandemic, the annual "Sardine Run" would attract tourists from across the globe. But this year, South African free diving champion Beth Neale was one of the few people who witnessed this phenomenon.
Armed with a GoPro and 360-camera, she swam beneath the big black slick of fish to film the incredible variety of marine wildlife it attracts. She believes her footage can help people appreciate how the ocean ecosystem depends on seemingly insignificant fish like the sardines.
"I know through seeing the beauty of the sardine run and the underwater world, people start to understand how connected everything is," Neale tells CNN. "From seeing a fish as something that's just a food source to seeing a fish as its integral role in the whole marine food chain and how that fish supplies so many marine animals."
A recent study in the South African Journal of Science shows changing weather patterns caused by the climate crisis may threaten the sardine run. It also means the sardines are migrating later in the year, which can cause food shortages for animals like the sharks that feed on them.
Protecting the oceans
The sardine run passes through some of South Africa's marine protected areas (MPAs), where fishing is restricted by law, giving sea life a chance to recover. Neale has been diving these waters for years and says she can see a significant difference between the areas that are safeguarded versus those that aren't. "The most amazing thing about the ocean is once you implement a marine protected area, you can see the change really, really rapidly," she says. South Africa is home to 42 MPAs , which aim to protect wildlife for the benefit of both nature and people. Prior to 2019, only 0.4% of the country's ocean territory was protected, but that has recently increased to 5.4% with a target of reaching 10%, says marine biologist Kerry Sink, who has played an instrumental role in advising the government on this expansion.
"The reason why it's really important to manage our fisheries well is because if we do that, we can fish forever," Sink tells CNN. "In a world with increasing pressure and increasing industrialization of the ocean,and in a time of climate change where there's even more uncertainty, we need to do everything that we can to have healthy oceans and healthy fish stocks."
Neale wholeheartedly agrees. "You protect what you love," she says. "The ocean is what I truly love the most."