Lemon Sharks: Baby Sharks That Live in Trees

SHOW NOTES

Living and working in Bimini, in the Bahamas, Jillian has come to know lemon sharks very well – so much so that she has even witnessed a female giving birth [8.10]! It’s rare to spend a lot of time in the water with sharks, let alone catch such a special and somewhat unpredictable event. But lemon sharks come into shallow waters to give birth to their pups – so shallow that they almost beach themselves! – to avoid predators and give their offspring the best chance at survival. Like most sharks, lemon sharks do not engage in any form of parental care. So, the newly born baby shark must fend for itself from the first moment it enters the water. Giving birth in shallow, protected environments, like mangrove forests, gives them a headstart. And because of this, scientists have a better idea of when and where lemon sharks will give birth than they do for most other species. It took a lot of time, and careful planning, but the event was filmed for the nature documentary Shark, on the BBC – which Jillian was able to be part of.  “Just seeing them so small and vulnerable, and seeing their life start…yeah, I believe it will remain one of the most amazing things I have ever seen.” She says.

But why are lemon sharks called lemon sharks in the first place [15.30]? Are they really bright yellow? “I always tell kids that I wish they were lemon yellow!” Laughs Jillian. “But I don’t think that would really work in the natural environment.” But they do have a slight yellow-ish tinge to their colouration, from which the name comes from. As a requiem shark (the same group to which bull and tiger sharks belong), they have a classic ‘sharky shape’ – a streamlined, torpedo-shaped body, which they share with many other species. But a distinguishing feature is that they have two dorsal fins, which are similar in size, and cat-like eyes.

Lemon sharks are also big fans of warm, tropical waters (who can blame them!) [20.35]. They are found along the east coast of the United States in the Atlantic, down through Florida, the Caribbean and the Gulf coast, and then further south into central and South America. There is also a small population on the west coast of Africa. Lemon sharks are largely a coastal species. They start out their life in mangrove ecosystems, which serve as an important nursery habitat for the young sharks (more on this later), before moving out into seagrass and coral reef habitats, where they feed primarily on other fishes, including sometimes other sharks!

Because of their preference for shallow, coastal habitats, and the fact that they cope relatively well in captivity, lemon sharks are some of the most well-studied elasmobranchs. Something Jillian has learned from her observations is that they are super flexible [22.30]! “I often see them biting their own tails.” She explains. “Lemon sharks would be excellent at yoga if they did it!” She isn’t exactly sure why they do this, but theorises it’s more of an accident, than a behaviour with a purpose. Their flexibility does give them an advantage, allowing them to be more manoeuvrable in order to catch fish, but Jillian believes sometimes their tail just gets in the way. “I’ve seen groups of them do this, when they’re hunting or trying to get away from something. The bite just kind of happens…it’s not like a shy shark that hides like that. But it does show you how flexible they are.” Another fun fact is that baby lemon sharks have belly buttons! Lemon sharks are viviparous, which means that the young are born live. Like in humans, baby sharks have a connection to the mother which is broken when they are born, leaving an umbilical scar on the underside of the shark. But unlike humans, it gradually fades over time. In fact, scientists look at how faded the scar is to get an idea of the age of a newborn shark.

Another interesting aspect about lemon sharks is their social behaviour [27.40]. Lemon sharks are often found hanging out in groups, or observed following one another. But this isn’t like you or I going out to grab a coffee or lunch with friends for the sake of companionship. Rather, it serves a biological purpose. There is such a thing as ‘safety in numbers’ – being in a group offers protection from predators, as it’s harder for a predator to select just one individual. It can also help sharks find food or shelter, especially the younger ones who are still learning how to be a lemon shark. “This shark, who is bigger and older than me, might know where to hide out if a large barracuda comes along, so I’m going to follow it.” Jillian explains. Younger sharks can learn from older or more experienced sharks the best routes through the complicated mangrove root systems, or where is good to hunt. It’s more of a case of gaining an advantage, as fun as it is to think of sharks with friends.

As we mentioned earlier, mangrove ecosystems are hugely important to lemon sharks [32.30]. Mangroves are salt-tolerant trees that grow along the water’s edge, and at certain times of the tide, their root systems can be completely submerged. This complicated tangle of roots and branches make the perfect hiding holes for small sharks, and protect them from larger predators whose size prevents them from gaining access. Many other animals use the mangroves for this purpose – including smaller fishes, crustaceans and molluscs – which means that there is plenty of food for a young shark too. The mangroves therefore provide the perfect nursery, supporting and protecting the baby lemon sharks until they are ready to make it out into the big, wide ocean.

But mangrove systems are also one of the most threatened habitats in the world [37.00]. Many mangrove forests have been removed to make way for coastal developments, taking away habitat that is vital for many species, especially in their early stages of life. This is in part why lemon sharks have been listed as Vulnerable on the IUCN Red List of Threatened Species. Lemon sharks are also threatened by fisheries. They are targeted in both commercial and artisanal fisheries, and caught as by-catch in other fisheries. The combination of these threats, and the scale of mangrove deforestation and overfishing, is driving lemon shark populations further into decline.

This brings us on very nicely to Project Lemon Aid, a collaboration between Sharks4Kids, the Big Blue Collective, the Turks and Caicos International Film Festival and the Edward Gartland Youth Center [38.40]. It started when Jillian and her partner Duncan attended a film festival in the Turks and Caicos to conduct outreach events, and as part of that visited a site where there were mangrove forests and baby lemon sharks. They discovered that there were nursery sites everywhere, but that they weren’t currently protected – although there were ideas for a sanctuary that had stalled due to a lack of data. And so, Project Lemon Aid was born, with the aim to aims to establish a base line population survey of juvenile lemon sharks at sites around the Turks and Caicos Islands. It involves tagging baby to sub-adult lemon sharks in inshore waters, and obtaining genetic samples from a tiny part of the dorsal fin. The team want to understand if females females return to the same mangroves they grew up in, and how the the Turks and Caicos population are linked to those in Florida and the Bahamas.

And a key part of Project Lemon Aid was the local community. “We thought, if we’re going to do this, the biggest thing we want that has to be part of it is students in the field. And training a local community to get involved – we want all the stakeholders involved.” Says Jillian. From the beginning, Project Lemon Aid has partnered with local education institutions, community groups, fisheries and diving and tourism operations to make sure that everyone has a seat at the table. “It’s far exceeded anything we’ve expected.” Jillian smiles. “It was formed from some wonderful conversations with some passionate people who wanted to find out what was happening with sharks, and that if data exists, if that can be used for better management. So it could be an MPA, it could be a no-take zone, full sanctuary, what’s going to happen…but we had to have a database, to start somewhere to find out what was happening with these sharks and make an informed decision.”

You can find out more about Project Lemon Aid here.

You can find out more about Sharks4Kids and how to get involved here.

And you can read more about lemon sharks here.

ABOUT OUR GUEST

Jillian Morris-Brake

Founder and President, Sharks4Kids

Born and raised in Maine, Jillian’s love for the ocean started at an early age and has continued to play an integral role in her adult life. She has spent thousands of hours in the field working and diving with sharks across the globe. She is a mom, marine biologist, shark conservationist, author, and educator.  She has filmed for numerous television shows and networks, has appeared on Shark Week and Shark Fest, and is a PADI Ambassadiver. She was named Scuba Diving Magazine’s July 2016 Sea Hero, awarded the inaugural Shark Con Shark Hero Award in 2017, and was the Go Blue Awards 2020 Blue Ambassador of the Year.  She is the author of Norman the Nurse Shark and Shark Super Powers and a member of the prestigious Ocean Artists Society.

Instagram: @biminisharkgirl

Twitter: @BiminiSharkGirl